Overheating and mysterious coolant loss common causes - reference
05-10-2011
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Overheating and mysterious coolant loss common causes - reference
First off, i never had an overheating except when on the track - i need a oil cooler...
Also, do not post questions here, no one wants to read for 100 pages of the same thing being asked continuously to find actual useful information.
I am currently trying to diagnose if my HG is actually starting to go bad...
Plus the annual influx of overheating threads are starting to raise since spring - talk about winter tires questions during fall, for example
Anyway, the thing is that the Civic engine is not diagnosed as most of the other cars, rarely you will see coolant in the oil, or oil in the coolant, or leakage or any other common diagnose for overheating.
The top culprit is: the head gasket going out. It will slowly let the combustion gases pass through the gasket to the coolant.
What then happens?
1) The gases will heat the coolant
2) The gases will create bubbles inside the engine, reducing heat transfer
3) The gases will push the collant out of the reservoir.
A good giveaway are:
1) if when you open the rad cap there is "air", not coolant.
2) Heater blows only cold air. (could be a dead heater core, though...)
3) Coolant overflows the coolant tank - This is already on the extreme cases.
If these symptons are there, perform a gases test in the coolant - since they are combustion gases, they will be detected.
If positive above, need to change the head gasket.
Now, comes the trick part: If you drove too long with it overheating, you run the chances that the head itself warped due to heat. If so, need to take head to a machine shop to ensure that the mounting surface is even, as to not allow leakage (if warped, the gasket cannot conform to the warped surface and the new gasket will simply let gases pass.
If the noted above is not your case, then start checking for fans not working, leakages, and oh, the radiator cap - use always the honda. Aftermarket ones tend to cause troubles.
If your case is not listed in here please post a new thread with your case and when solved, it will be later updated in here.
There is another thread, but it is more general so i thought it could be misleading - it was not written for hondas.
https://www.civicforums.com/forums/7...ml#post1862929
one iof the last posters did correct the info, so i am posting it with the gasket in the top.
how to test? cheap way 1:(Thanks, ezone!, including your "own style" comment :P)
Half of the bad head gaskets I see on this engine will pass every test you guys have mentioned. These almost never leak externally. These almost always leak from the combustion chamber into the cooling system, and that's it. That's all.
My procedure:
Start with a hot engine, pull out plugs and rad cap:
Pressurize each cylinder (@TDC, one at a time) with shop air line pressure 150-170+ PSI. Watch for the coolant level to rise when you get to the bad one. (sometimes this is a slow process)
If no results, then wait for the engine to cool down and repeat this same procedure on each cylinder.
If it passes this test, then it's probably ok right now. EDIT (by ezone): Now with video goodness
see original thread here - more details in there.
https://www.civicforums.com/forums/3...-ex-coupe.html
how to test? cheap way 2: Thanks, Scotty!)
If anyone have more insight info, feel free to contribute
regards
Also, do not post questions here, no one wants to read for 100 pages of the same thing being asked continuously to find actual useful information.
I am currently trying to diagnose if my HG is actually starting to go bad...
Plus the annual influx of overheating threads are starting to raise since spring - talk about winter tires questions during fall, for example
Anyway, the thing is that the Civic engine is not diagnosed as most of the other cars, rarely you will see coolant in the oil, or oil in the coolant, or leakage or any other common diagnose for overheating.
The top culprit is: the head gasket going out. It will slowly let the combustion gases pass through the gasket to the coolant.
What then happens?
1) The gases will heat the coolant
2) The gases will create bubbles inside the engine, reducing heat transfer
3) The gases will push the collant out of the reservoir.
A good giveaway are:
1) if when you open the rad cap there is "air", not coolant.
2) Heater blows only cold air. (could be a dead heater core, though...)
3) Coolant overflows the coolant tank - This is already on the extreme cases.
If these symptons are there, perform a gases test in the coolant - since they are combustion gases, they will be detected.
If positive above, need to change the head gasket.
Now, comes the trick part: If you drove too long with it overheating, you run the chances that the head itself warped due to heat. If so, need to take head to a machine shop to ensure that the mounting surface is even, as to not allow leakage (if warped, the gasket cannot conform to the warped surface and the new gasket will simply let gases pass.
If the noted above is not your case, then start checking for fans not working, leakages, and oh, the radiator cap - use always the honda. Aftermarket ones tend to cause troubles.
If your case is not listed in here please post a new thread with your case and when solved, it will be later updated in here.
There is another thread, but it is more general so i thought it could be misleading - it was not written for hondas.
https://www.civicforums.com/forums/7...ml#post1862929
one iof the last posters did correct the info, so i am posting it with the gasket in the top.
^^^ actually the people who know alot have HAD OR are having the problems arent saying much cause this is a common problem and if u DO know what ur talking about like some of us do. THEN u can easily reconize the symptoms and fix the gasket in a coupe hours time.
needless to say that 99% of modified Honda's meaning MODIFIED..(turbo,nos,full built N/A job.etc...) have this problem.
the fastest honda's todate still use oem gaskets and let them BLOW..
its better to have a gasket blow, reconize it, fix it for 30 bucks and move on... then have a heavy duty gasket.. hold up and risk the engine blowning via broken rods, pistons, block... and have to start all over with a new engine.
so THAT IS why so many head gaskets blow..
needless to say that 99% of modified Honda's meaning MODIFIED..(turbo,nos,full built N/A job.etc...) have this problem.
the fastest honda's todate still use oem gaskets and let them BLOW..
its better to have a gasket blow, reconize it, fix it for 30 bucks and move on... then have a heavy duty gasket.. hold up and risk the engine blowning via broken rods, pistons, block... and have to start all over with a new engine.
so THAT IS why so many head gaskets blow..
Compression test will not show you this problem.
I would stick a funnel-fill funnel on the radiator
and let it run, watch for an endless slow stream of bubbles coming up.
If the engine seems to never finish burping its air out, then my next step is to put shop air pressure on each cylinder to see and prove which one is leaking.
I'm darn lazy and I don't like pulling a head without definite proof, and that test is proof enough for me.
You have read threads where I talk more about this method, right?
I would stick a funnel-fill funnel on the radiator
and let it run, watch for an endless slow stream of bubbles coming up.
If the engine seems to never finish burping its air out, then my next step is to put shop air pressure on each cylinder to see and prove which one is leaking.
I'm darn lazy and I don't like pulling a head without definite proof, and that test is proof enough for me.
You have read threads where I talk more about this method, right?
Half of the bad head gaskets I see on this engine will pass every test you guys have mentioned. These almost never leak externally. These almost always leak from the combustion chamber into the cooling system, and that's it. That's all.
My procedure:
Start with a hot engine, pull out plugs and rad cap:
Pressurize each cylinder (@TDC, one at a time) with shop air line pressure 150-170+ PSI. Watch for the coolant level to rise when you get to the bad one. (sometimes this is a slow process)
If no results, then wait for the engine to cool down and repeat this same procedure on each cylinder.
If it passes this test, then it's probably ok right now.
see original thread here - more details in there.
https://www.civicforums.com/forums/3...-ex-coupe.html
how to test? cheap way 2: Thanks, Scotty!)
Good numbers. Well under 10% variation too.
Stick the reservoir hose in a container of water set up where you can see it, watch for bubbles coming up while you let it run?
All you need is a way to see the coolant level change or air bubbles coming up through it. I mentioned the funnel because that is what I use, most convenient for me.
Some of them don't want to leak much until the engine has a load on it, and pressure in the radiator reduces how much gets past the head gasket.
It's like $32, and damn handy if you do any regular work on cars. http://www.amazon.com/Lisle-24610-Sp.../dp/B001A4EAV0
Too many will pass this test, yet still have a head gasket problem. Not reliable enough for me.
Correct.
Stick the reservoir hose in a container of water set up where you can see it, watch for bubbles coming up while you let it run?
All you need is a way to see the coolant level change or air bubbles coming up through it. I mentioned the funnel because that is what I use, most convenient for me.
Some of them don't want to leak much until the engine has a load on it, and pressure in the radiator reduces how much gets past the head gasket.
It's like $32, and damn handy if you do any regular work on cars. http://www.amazon.com/Lisle-24610-Sp.../dp/B001A4EAV0
Too many will pass this test, yet still have a head gasket problem. Not reliable enough for me.
Correct.
So blown head gasket it is then
I attached some rubber tubing to where the overflow reservoir hose attaches to the radiator filler neck and immersed the other end in an open container full of coolant. Please see attached video to the see the bubbles:
There are no bubbles at idle but you can clearly see a stream of bubbles when I rev it up.
Is this enough confirmation of a blown HG to warrant removing the head and replacing the gasket?
I attached some rubber tubing to where the overflow reservoir hose attaches to the radiator filler neck and immersed the other end in an open container full of coolant. Please see attached video to the see the bubbles:
There are no bubbles at idle but you can clearly see a stream of bubbles when I rev it up.
Is this enough confirmation of a blown HG to warrant removing the head and replacing the gasket?
If anyone have more insight info, feel free to contribute
regards
Last edited by ezone; 12-19-2015 at 04:17 PM.
05-10-2011
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There is a systematic sequence of events you have to go through to diagnose a head gasket. The way 99% people realize something is wrong is when their car starts overheating and the overflow is full to the top and the heat only blows hot when moving, not when idling. But hold your horses, it might not be a head gasket yet.
If the overflow tank is overfilling skip step #1-2.
1. Check your fans to make sure they are turning on and functioning properly, if not you need to replace either the fans themselves, the switches or relays.
2. You need to bleed the coolant system of air, which consists of jacking up the front of the car while it is cold. Removing the radiator cap, starting the car and turning the heat on full heat full blast. As the radiator drains down you need to refill it with OEM Honda coolant. Once the air is all bled out I lower the car back on its wheels, leave the radiator cap off overnight and top up the radiator in the morning. You will notice it has gone down a little bit top it up, put the rad cap back on and off you go. If however, the overheating problem comes back go to step #3.
3. A thermostat and radiator cap are common causes of air getting into the cooling system. They tend to age and are actually part of a cars regular maintenance. Since your POS is overheating, change them out and repeat step #2. If the overheating continues go to step #4.
4. Great, the cheap stuff is out of the way, now it's probably a head gasket... if the overflow however is not overfilling it could still be a water pump or a clog in the system. Unlikely though, since there are about a hundred threads a week here about people asking whats going on with their head gasket. On to step #5...
5. Now it's time to check for exhaust gases in the coolant system. The absolute best method is not a leak down test... or a pressure test because it may miss the problem. The best way hands down is a combustion leak test, where they check for actual exhaust in the radiator. Hell, here is a great video of Scotty Kilmer doing it:
[autostream]http://autostream.com/ibcivicforums/?page_type=firebirdplayerthumbnail&framepage=122&t ransactionid=1305049178-1732384843&posted_by=tbohar_www.civicforums.com&yo utube_video_id=QA7KVQq9vKA[/autostream]
If you don't discover exhaust gases in the rad, the car is not blowing white smoke, spark plugs or oil cap are not white... your coolant system may be plugged up somewhere causing overheating. However, you car does not have to blow white smoke, have white spark plugs or oil cap in order for it to be the head gasket... it could be blown and not be showing any symptoms whatsoever except overheating/full overflow. On to step #6, and yes it's gonna hurt.
6. Time to start taking crap apart... start removing the head using hondas awesome service manual... when you get to the timing belt portion remove the water pump and make sure it's okay. If you find the water pump is corroded or some of the blades are gone replace it. Do go on and replace your head gasket anyway though. Your not only halfway there but if you detected gases in the exhaust system it is guaranteed to be the HG.
7. Head gaskets tend to blow because of an underlying problem that caused the car to overheat. You should do your due diligence and find out what the initial problem was or you risk blowing your head gasket again. Or you can just rely on it being the thermostat or rad cap which youve already replaced. Keep a close eye on your temp gauge after you repair it. THhe last thing you wanna be doing is replacing it again a few months later.this thread.
I hope this helps some people diagnose their head gasket issues. Anyone that asks as to why they are overheating on this forum should be pointed straight to this thread.
Great job sdaidoji... Stickied
If the overflow tank is overfilling skip step #1-2.
1. Check your fans to make sure they are turning on and functioning properly, if not you need to replace either the fans themselves, the switches or relays.
2. You need to bleed the coolant system of air, which consists of jacking up the front of the car while it is cold. Removing the radiator cap, starting the car and turning the heat on full heat full blast. As the radiator drains down you need to refill it with OEM Honda coolant. Once the air is all bled out I lower the car back on its wheels, leave the radiator cap off overnight and top up the radiator in the morning. You will notice it has gone down a little bit top it up, put the rad cap back on and off you go. If however, the overheating problem comes back go to step #3.
3. A thermostat and radiator cap are common causes of air getting into the cooling system. They tend to age and are actually part of a cars regular maintenance. Since your POS is overheating, change them out and repeat step #2. If the overheating continues go to step #4.
4. Great, the cheap stuff is out of the way, now it's probably a head gasket... if the overflow however is not overfilling it could still be a water pump or a clog in the system. Unlikely though, since there are about a hundred threads a week here about people asking whats going on with their head gasket. On to step #5...
5. Now it's time to check for exhaust gases in the coolant system. The absolute best method is not a leak down test... or a pressure test because it may miss the problem. The best way hands down is a combustion leak test, where they check for actual exhaust in the radiator. Hell, here is a great video of Scotty Kilmer doing it:
[autostream]http://autostream.com/ibcivicforums/?page_type=firebirdplayerthumbnail&framepage=122&t ransactionid=1305049178-1732384843&posted_by=tbohar_www.civicforums.com&yo utube_video_id=QA7KVQq9vKA[/autostream]
If you don't discover exhaust gases in the rad, the car is not blowing white smoke, spark plugs or oil cap are not white... your coolant system may be plugged up somewhere causing overheating. However, you car does not have to blow white smoke, have white spark plugs or oil cap in order for it to be the head gasket... it could be blown and not be showing any symptoms whatsoever except overheating/full overflow. On to step #6, and yes it's gonna hurt.
6. Time to start taking crap apart... start removing the head using hondas awesome service manual... when you get to the timing belt portion remove the water pump and make sure it's okay. If you find the water pump is corroded or some of the blades are gone replace it. Do go on and replace your head gasket anyway though. Your not only halfway there but if you detected gases in the exhaust system it is guaranteed to be the HG.
7. Head gaskets tend to blow because of an underlying problem that caused the car to overheat. You should do your due diligence and find out what the initial problem was or you risk blowing your head gasket again. Or you can just rely on it being the thermostat or rad cap which youve already replaced. Keep a close eye on your temp gauge after you repair it. THhe last thing you wanna be doing is replacing it again a few months later.this thread.
I hope this helps some people diagnose their head gasket issues. Anyone that asks as to why they are overheating on this forum should be pointed straight to this thread.
Great job sdaidoji... Stickied
Last edited by BlueEM2; 05-10-2011 at 12:45 PM.
05-10-2011
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greeeat! more complete and better than mine. Now we don't need to be like parrots and repeat the same stuff all the time thanks, tom!
thanks, tom! The following users liked this post:
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05-10-2011
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No problem, I've been meaning to write this up for a while I just have never gotten around to it. I hope I didn't step on your toes by adding a bunch to it. Another quality stick by you my friend!
05-10-2011
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nooot at all! As i said in the first post, i am still stepping in the diagnosys itself, but the sheer amount of the threads daily was... hard...
you will be also helping me to see if my HG is actually bad or good enough for the upcoming 1200 mile trip... I wanted to do it during the timing belt that is coming too... and the stage 1 cam (which can be written off if the engine... deceases itself...)
you will be also helping me to see if my HG is actually bad or good enough for the upcoming 1200 mile trip... I wanted to do it during the timing belt that is coming too... and the stage 1 cam (which can be written off if the engine... deceases itself...)
05-10-2011
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Re: Overheating common causes - reference
Epically awesome job guys. Hopefully this will steer a lot of these people in the right direction. I don't mean to get a little off of the tips, but I didn't need to jack my car up when I changed my coolant. I just ran the car with the cap off and let the bubbles blow out and kept adding coolant until the rad was topped off and no more bubbles were coming out. I just went by my manual, so the 7th gens might have a different procedure?
05-10-2011
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Hmm... to be honest with you MelJ I don't know why we jack the car up, I was just always told to. I think it has something to do with getting air that resides in the heater core out... possibly bringing the core lower than the radiator but I could be wrong. Someone correct me please.
05-10-2011
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Re: Overheating common causes - reference
Yeah. When I was reading it, that's what I was thinking as well. I think I actually saw that same response back when I first started working on my car and being on this site. It makes sense, though.
05-10-2011
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I just did a bit of research and it helps burp the air out for some reason... Still haven't found a concrete answer to your question... I'm no mechanic though so maybe someone can chime in here that may know the cooling system better than I do.
05-10-2011
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ah, it's about the air - it tends to go up when in a liquid environment - so if the rad is higher than the engine, it will burp more air easier
05-15-2011
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From the most recent thread, i am adding an very important missing piece of information in here....
USE OEM Honda radiator cap and thermostat - aftermarket ones are well known for causing problems
https://www.civicforums.com/forums/1...ease-help.html
USE OEM Honda radiator cap and thermostat - aftermarket ones are well known for causing problems
https://www.civicforums.com/forums/1...ease-help.html
get an oem cap and thermostat. some stupid shop had put an aftermarket thermo in our accord and it always ran slightly hot and the fans would come on every minute. finally it started to actually overheat past the 1/2 way mark on the gauge so i took the thermo out and thats the first thing i noticed how crappy it looked compared to the honda part i used. not to mention, the aftermarket was barely opening compared to the oem. swapped in the oem and it was like a new car again. usually aftermarket replacement parts are crap and nowhere near what oem is like. i know someone else who thought a cheap radiator cap from the store was fine, next thing you know coolant is coming out of the waterpump and his hoses were swelling. im guessing the pressure was too much or the cap wasnt working properly.
05-31-2011
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Re: Overheating common causes - reference
Thanks for all the good info that ultimately led to me swap my head gasket. I too was experiencing raising temps while stopped and idling but not while driving. I didn't want to accept that it was a blown gasket but there was no way around it. I ended up swapping a few valves and all the seals in my cylinder head while I had the chance. Thanks for helping me pinpoint the problem before I did any more serious damage.
This thread wins!
06-08-2011
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After reading this thread, I'm pretty sure my HG is bad, I'm overflowing the jug, and it will not suck the coolant back in when it cools down. No steam, no antifreeze in the oil, but after a couple hundred miles, the temp will start to go up while sitting, and I have to add coolant. For now, I have just been adding every few days to be safe.
Anyone know what a shop normaly charges to do this? Taking into account, changing timing belt and water pump, since they are in there already.
Not something I feel like working on myself. Would be a different story if it were my 72 olds 442
Anyone know what a shop normaly charges to do this? Taking into account, changing timing belt and water pump, since they are in there already.
Not something I feel like working on myself. Would be a different story if it were my 72 olds 442
09-02-2011
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hunh.
If the temp gauge jumps on when car is cold, need to check the gauges too. they might be shorting or else.
https://www.civicforums.com/forums/1...ar-normal.html
If the temp gauge jumps on when car is cold, need to check the gauges too. they might be shorting or else.
https://www.civicforums.com/forums/1...ar-normal.html
10-02-2011
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From recent threads (many), it seems that the gas in the coolant tester is not really reliable...
Not sure of the causes, but if you have a coolant overflow from the reservoir, fans working, gauges OK, OEM cap and thermo, etc, etc, just bite the bullet and go for the headgasket. You will end up saving time and money (especially if engine overheats, which means machining the head...).
Not sure of the causes, but if you have a coolant overflow from the reservoir, fans working, gauges OK, OEM cap and thermo, etc, etc, just bite the bullet and go for the headgasket. You will end up saving time and money (especially if engine overheats, which means machining the head...).
11-06-2011
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here goes a good collection of factors and things to check from our good fella GB:
thanks, buddy!
are the lower and upper large radiator hoses too hot to touch after driving the car? if so the thermostat is good. if the lower hose is only warm or cold, bad thermostat. is the coolant overflow (plastic white tank) full of coolant and leaking from the top? when overheating, does the temp gauge go down if you turn the fan to max and temp to HOT? does hot air blow from the vents? the radiator fan actually does very little to cool the motor unless you are stopped in traffic for long periods of time in the summer. you can also try to feel different areas of the radiator to see if certain areas are cold, which would indicate clogs. also i think you two drove the car way too much and caused a small problem to become worse. im not sure what a transmission light is, these cars dont have one unless you mean the engine light, or the D icon was flashing. have the code checked for free at the auto store and post back what it was.
11-08-2011
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good god...
steve went on a row in that thread... great!
steve went on a row in that thread... great!
the easiest way to figure this stuff out is start small and work your way up. head gasket should be the last thing to worry about, altho they seem to be pretty common on these cars. i have a feeing its due to people inadvertently (or on purpose, thanks honda owners manual) driving their car in winter til the temp gauge reads in the middle/normal, then cranking the temp dial from cold to hot. on this particular gen, this opens a large heater hose valve and allows ice cold coolant sitting in the heater core and dash hoses to go straight into the hot engine head. as you can guess, this is really bad for the engine. instead, leave the temp dial on hot for the whole winter and just turn the fan to OFF before the car warms up. this allows the car to still warm up fairly quickly, and you will have all the coolant circulating already when the car is warmed up. then adjust the fan speed to your liking or leave it off and air will blow in when driving on its own. on the freeway, i doubt you even need the blower fan at all.
anyway, ordered list of overheating checks:
1. thermostat. drive the car til its fully warmed up, at least 30mins. open hood and feel top and bottom radiator hoses (the big ones). top should be hot, bottom should be hot. this means coolant is going to the radiator and everything is normal. if bottom hose is cool or warm, thermostat is either stuck closed or not opening enough. can cause overheating under certain conditions. solution: replace with oem honda thermostat.
2. fan motor, fan relay, fan fuse, or fan temp sensor. something is causing the cooling fans to not come on like they should when the car is at idle for extended periods of time in hot weather. turn the a/c on and see if both fans come on immediately. if so, motor/fuse/relay is fine. fan temp sensor in the coolant passage could be bad. on a hot summer day, outside temp of 90F or higher, drive the car til it warms up fully. park car and leave it running. within 5 mins the fans should turn on. if not, bad fan temp sensor. replace it and retest. a fan problem can cause overheating at idle in stop and go traffic, but not while the car is driving above 35mph (then the radiator will be doing its job).
3. air bubbles. can cause real or fake overheating. air in the cooling system is usually caused by doing a coolant drain and fill on these cars, since the radiator passages are so tiny compared to cars with larger engines. air bubbles around the cooling passages can cause hotspots to develop, which can cause serious problems with the engine. air does not cool anywhere near as good as liquid. air can also confuse the engine coolant temp (ECT) sensor and cause it to read a higher than normal temp. the sensor must be inside the coolant to work properly. to limit air bubble formation when doing a coolant change, you can turn the temp dial to full COLD before shutting off the car. you can also choose not to open the engine block drain bolt. note that doing these things will allow some old coolant to stay in the system. so you may want to do a second drain and fill later on once the new and old coolant mixes. after coolant change, make sure you bleed the majority of air out by following this procedure. drive car til fully warmed up. park on a sharp upward incline or jack up front of car. carefully remove radiator cap using a lot of shop towels to catch the coolant spray. leave cap off, start car, turn temp dial to max HOT. turn fan on one notch. feel the air coming out. if cool, you have a long way to go. watch the radiator and add coolant so that you can see the level near the top. keep watching for air bubbles for at least 30 mins, or until no large bubbles are coming to the surface. you can tap or squeeze the large radiator hoses and rev the engine to 3k rpms occasionally to speed up the process. when bubble formation has stopped, put cap back on and turn off car. go for a drive and turn the fan on. hot burning air should be coming from the vents. some water bubbling noises may be heard in the dash for up to a year afterwards, but these small bubbles will eventually come out. make sure the temp gauge does not go above normal.
4. radiator cap. a faulty cap that does not pop open and allow coolant into the overflow tank can cause cooling system pressure to rise above normal. this can lead to hoses failing, water pump leaking, and a variety of other problems that can make it seem like a headgasket leak. replace cap with a new honda oem part every 5 yrs to prevent any problems.
5. ECT sensor. already mentioned, this sensor is extremely important. not only does it tell you how hot the coolant is (via the temp gauge), it also tells the ecu so it can adjust how the car runs. usually you will get a check engine light for a bad sensor, but not always. replace this if you seem to be overheating for no real reason, and the engine bay does not seem to be hotter than normal and the coolant level is normal.
6. clogged radiator, cooling system, or other. if you have an older car where the coolant was never changed, chances are you have junk inside that could be clogging parts of the cooling system. you can check for radiator clogs by warming up the car, then using an IR thermometer to check the temp of various areas of the radiator. if one or more spots are very cool, you may have a blockage. if you drain the coolant and find any sort of debris, try a power flush of the system and hope that most of the chunks work their way out. it can be a huge challenge to clean up a cooling system like this because there are so many small passages where clogs can occur.
7. physical coolant leaks. if you are losing coolant and there are visible leaks, trace where they are coming from and fix the leak (hose, water pump, engine block, etc). failure to fix leaks can result in overheating when enough coolant is lost. if the overflow tank becomes empty, the cooling system can suck in air and make the situation even worse.
8. head gasket. you finally arrived. it wasnt easy, but now you are almost sure the overheating is caused by a gasket leak between the engine head and block. how can you make sure? lots of ways. a large leak can easily be detected by checking the compression of each cylinder. the stock rating is roughly 128 psi, but you are looking more for one or two cylinders that are very low compared to the rest. with a small gasket leak, compression can come back normal on all cylinders. if the oil looks milky, and the coolant looks oily, more than likely the two are mixing together. if you have a misfire when cold starting the car (whole car is shaking violently for a minute), that can be an indication of a slow leak where coolant is filling one or more cylinders. when the car warms up, the coolant burns away and car runs fine. you can have the cooling system pressure checked as well. lower pressure can mean a physical leak or also a gasket leak. pull all the spark plugs and look for white deposits that can indicate burnt coolant.do a gas test of the coolant that can indicate the presence of hydrocarbons leaking in from combustion. be complete and do as many tests as you can. a blown headgasket, if small, can be driven on for a while. but it will get worse and can eventually cause serious damage, even if you are not overheating right now. usually coolant that disappears from the reservoir with no reason always points to it being burned in the engine from a headgasket leak.
now some ideas if your car is not overheating, but there is no cabin heat from the heater vents. drive the car to normal operating temp and leave it on. look in the back of the engine bay where there are two smaller cooling hoses going into the dash. on one hose there is a black valve assembly with a metal lever and cable assembly (usually blue cable). inside the car, turn the temp dial from full hot to full cold. make sure the lever moves completely from one side to the other. this opens the cooling passage and allows hot engine coolant to come inside the cabin and heater core (small radiator in the dash). after a minute or two of turning the temp dial to hot, feel the two heater hoses going into the dash. they should both be warm to hot. it is okay if one hose is hotter than the other (this is hot engine coolant going into the dash). the cooler hose is coolant that has already been used to heat the cabin. if you have the fan blowing hard, one hose will always be less hot than the other. with fan turned off, they should be similar temps. inside the car, remove the driver side lower fuse cover and stick your head up on the gas pedal side. you should see a bunch of plastic gears and an actuator motor. turn the temp dial from full hot to full cold. the gears should move for a few seconds (they may not be smoothly turning, but they should move). now turn the temp dial one notch at a time. each notch should turn the gears very quickly for a split second. if you hear no noise and gears are not moving, replace the actuator motor. if gears are slow or struggling but motor is working, the engine bay heater hose valve may be sticking. spray it with silicone to see if it moves faster. if not, replace the heater valve. do not attempt to manually turn the heater valve using the metal lever. you can break it. if everything checks out but you are not getting hot air blowing, it could be a problem with either the blower motor or transistor.
anyway, ordered list of overheating checks:
1. thermostat. drive the car til its fully warmed up, at least 30mins. open hood and feel top and bottom radiator hoses (the big ones). top should be hot, bottom should be hot. this means coolant is going to the radiator and everything is normal. if bottom hose is cool or warm, thermostat is either stuck closed or not opening enough. can cause overheating under certain conditions. solution: replace with oem honda thermostat.
2. fan motor, fan relay, fan fuse, or fan temp sensor. something is causing the cooling fans to not come on like they should when the car is at idle for extended periods of time in hot weather. turn the a/c on and see if both fans come on immediately. if so, motor/fuse/relay is fine. fan temp sensor in the coolant passage could be bad. on a hot summer day, outside temp of 90F or higher, drive the car til it warms up fully. park car and leave it running. within 5 mins the fans should turn on. if not, bad fan temp sensor. replace it and retest. a fan problem can cause overheating at idle in stop and go traffic, but not while the car is driving above 35mph (then the radiator will be doing its job).
3. air bubbles. can cause real or fake overheating. air in the cooling system is usually caused by doing a coolant drain and fill on these cars, since the radiator passages are so tiny compared to cars with larger engines. air bubbles around the cooling passages can cause hotspots to develop, which can cause serious problems with the engine. air does not cool anywhere near as good as liquid. air can also confuse the engine coolant temp (ECT) sensor and cause it to read a higher than normal temp. the sensor must be inside the coolant to work properly. to limit air bubble formation when doing a coolant change, you can turn the temp dial to full COLD before shutting off the car. you can also choose not to open the engine block drain bolt. note that doing these things will allow some old coolant to stay in the system. so you may want to do a second drain and fill later on once the new and old coolant mixes. after coolant change, make sure you bleed the majority of air out by following this procedure. drive car til fully warmed up. park on a sharp upward incline or jack up front of car. carefully remove radiator cap using a lot of shop towels to catch the coolant spray. leave cap off, start car, turn temp dial to max HOT. turn fan on one notch. feel the air coming out. if cool, you have a long way to go. watch the radiator and add coolant so that you can see the level near the top. keep watching for air bubbles for at least 30 mins, or until no large bubbles are coming to the surface. you can tap or squeeze the large radiator hoses and rev the engine to 3k rpms occasionally to speed up the process. when bubble formation has stopped, put cap back on and turn off car. go for a drive and turn the fan on. hot burning air should be coming from the vents. some water bubbling noises may be heard in the dash for up to a year afterwards, but these small bubbles will eventually come out. make sure the temp gauge does not go above normal.
4. radiator cap. a faulty cap that does not pop open and allow coolant into the overflow tank can cause cooling system pressure to rise above normal. this can lead to hoses failing, water pump leaking, and a variety of other problems that can make it seem like a headgasket leak. replace cap with a new honda oem part every 5 yrs to prevent any problems.
5. ECT sensor. already mentioned, this sensor is extremely important. not only does it tell you how hot the coolant is (via the temp gauge), it also tells the ecu so it can adjust how the car runs. usually you will get a check engine light for a bad sensor, but not always. replace this if you seem to be overheating for no real reason, and the engine bay does not seem to be hotter than normal and the coolant level is normal.
6. clogged radiator, cooling system, or other. if you have an older car where the coolant was never changed, chances are you have junk inside that could be clogging parts of the cooling system. you can check for radiator clogs by warming up the car, then using an IR thermometer to check the temp of various areas of the radiator. if one or more spots are very cool, you may have a blockage. if you drain the coolant and find any sort of debris, try a power flush of the system and hope that most of the chunks work their way out. it can be a huge challenge to clean up a cooling system like this because there are so many small passages where clogs can occur.
7. physical coolant leaks. if you are losing coolant and there are visible leaks, trace where they are coming from and fix the leak (hose, water pump, engine block, etc). failure to fix leaks can result in overheating when enough coolant is lost. if the overflow tank becomes empty, the cooling system can suck in air and make the situation even worse.
8. head gasket. you finally arrived. it wasnt easy, but now you are almost sure the overheating is caused by a gasket leak between the engine head and block. how can you make sure? lots of ways. a large leak can easily be detected by checking the compression of each cylinder. the stock rating is roughly 128 psi, but you are looking more for one or two cylinders that are very low compared to the rest. with a small gasket leak, compression can come back normal on all cylinders. if the oil looks milky, and the coolant looks oily, more than likely the two are mixing together. if you have a misfire when cold starting the car (whole car is shaking violently for a minute), that can be an indication of a slow leak where coolant is filling one or more cylinders. when the car warms up, the coolant burns away and car runs fine. you can have the cooling system pressure checked as well. lower pressure can mean a physical leak or also a gasket leak. pull all the spark plugs and look for white deposits that can indicate burnt coolant.do a gas test of the coolant that can indicate the presence of hydrocarbons leaking in from combustion. be complete and do as many tests as you can. a blown headgasket, if small, can be driven on for a while. but it will get worse and can eventually cause serious damage, even if you are not overheating right now. usually coolant that disappears from the reservoir with no reason always points to it being burned in the engine from a headgasket leak.
now some ideas if your car is not overheating, but there is no cabin heat from the heater vents. drive the car to normal operating temp and leave it on. look in the back of the engine bay where there are two smaller cooling hoses going into the dash. on one hose there is a black valve assembly with a metal lever and cable assembly (usually blue cable). inside the car, turn the temp dial from full hot to full cold. make sure the lever moves completely from one side to the other. this opens the cooling passage and allows hot engine coolant to come inside the cabin and heater core (small radiator in the dash). after a minute or two of turning the temp dial to hot, feel the two heater hoses going into the dash. they should both be warm to hot. it is okay if one hose is hotter than the other (this is hot engine coolant going into the dash). the cooler hose is coolant that has already been used to heat the cabin. if you have the fan blowing hard, one hose will always be less hot than the other. with fan turned off, they should be similar temps. inside the car, remove the driver side lower fuse cover and stick your head up on the gas pedal side. you should see a bunch of plastic gears and an actuator motor. turn the temp dial from full hot to full cold. the gears should move for a few seconds (they may not be smoothly turning, but they should move). now turn the temp dial one notch at a time. each notch should turn the gears very quickly for a split second. if you hear no noise and gears are not moving, replace the actuator motor. if gears are slow or struggling but motor is working, the engine bay heater hose valve may be sticking. spray it with silicone to see if it moves faster. if not, replace the heater valve. do not attempt to manually turn the heater valve using the metal lever. you can break it. if everything checks out but you are not getting hot air blowing, it could be a problem with either the blower motor or transistor.
01-27-2012
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Re: Overheating common causes - reference
ok i have a confusing problem on my hands..... i have a 2001 Civic Lx. It was overheating with physical visual leaks coming from radiator due to corrosion.... i replaced radiator.... bled it with all bubbles out, still overheating, i felt the top and bottom radiator hoses and found bottom one is cold while at operating temperature... so i replaced thermostat, bled it with no bubbles..... drove car for 30 miles got heat and all and no overheating.... now just got off highway temp readings start to creep up to H.... popped hood and found coolant sprayed everywhere from resevoir.... im starting to think this might end up being a major problem.....thank you for your time!
01-27-2012
#20
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did you even read any words of what is written above? also, no questions in here, it clutters the thread and important info could get lost. this is for reference, not for asking.
It is right there in the first post, actually... that shows how much you did read...
"Also, do not post questions here, no one wants to read for 100 pages of the same thing being asked continuously to find actual useful information."
It is right there in the first post, actually... that shows how much you did read...
"Also, do not post questions here, no one wants to read for 100 pages of the same thing being asked continuously to find actual useful information."
01-28-2012
#21
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Hmm.. Sandro, this is your thread. Do you want me to close it and leave it as a reference thread?
Andy, your head gasket is shot.
Andy, your head gasket is shot.
01-28-2012
#22
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thanks, Tom, but no.
I still want to keep it open, so anyone that have useful info or is not listed here can chime in and add to the usefullness of it. (which clearly was not the last case, he did not even read through the thread at all... so there was not even point in responding, since he cannot read anyway.)
I still want to keep it open, so anyone that have useful info or is not listed here can chime in and add to the usefullness of it. (which clearly was not the last case, he did not even read through the thread at all... so there was not even point in responding, since he cannot read anyway.)
06-07-2012
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thanks, JonDorian!
I think this thread is pretty well covered- but I'll share my story to make sure - pretty frustrating - I did not expect this when I bought my Honda
02 Civic EX with intermittent cooling issues - at around 150K it started overheating when slowing down getting off highway (water pump and tb were replaced at 130K)
replaced thermostat and radiator cap - no luck...replaced whole radiator..no luck..
noticed disappearing coolant - was disappearing faster and faster - no external leaks
tried combustion leak check to test for combustion gases and it did not detect any problems - no white smoke out of tail pipe, spark plugs looked OK
So - really the only signs of HG failure I had were overheating when slowing down (and over time it even happened at highway speeds), extra coolant in the reservoir, and mysteriously disappearing coolant with no external leaks
I pulled the head - gasket itself looked OK - but I took the head to an engine machine shop and the owner told me right away the gasket was blown at spots in all 4 cylinders - and he sees about 2-3 of these per week from Civics.
Charged me $80 to clean and resurface the head - said it wasn't warped too bad and he only had to take a little off (I don't remember exactly what he said)
IMHO - If you don't take your head to a professional machine shop that works on engines while its apart I personally think you're crazy. Too big of a job to take the chance that its fine and slap on a new gasket
Reinstalled head with a Fel-Pro Gasket - reused original head bolts (torque like you're supposed to) and have driven 1000 miles without any coolant loss or overheating
Sorry to anyone who has this misfortune - I don't see my next car being a Honda...but if you have symptoms like mine good chance its your HG
02 Civic EX with intermittent cooling issues - at around 150K it started overheating when slowing down getting off highway (water pump and tb were replaced at 130K)
replaced thermostat and radiator cap - no luck...replaced whole radiator..no luck..
noticed disappearing coolant - was disappearing faster and faster - no external leaks
tried combustion leak check to test for combustion gases and it did not detect any problems - no white smoke out of tail pipe, spark plugs looked OK
So - really the only signs of HG failure I had were overheating when slowing down (and over time it even happened at highway speeds), extra coolant in the reservoir, and mysteriously disappearing coolant with no external leaks
I pulled the head - gasket itself looked OK - but I took the head to an engine machine shop and the owner told me right away the gasket was blown at spots in all 4 cylinders - and he sees about 2-3 of these per week from Civics.
Charged me $80 to clean and resurface the head - said it wasn't warped too bad and he only had to take a little off (I don't remember exactly what he said)
IMHO - If you don't take your head to a professional machine shop that works on engines while its apart I personally think you're crazy. Too big of a job to take the chance that its fine and slap on a new gasket
Reinstalled head with a Fel-Pro Gasket - reused original head bolts (torque like you're supposed to) and have driven 1000 miles without any coolant loss or overheating
Sorry to anyone who has this misfortune - I don't see my next car being a Honda...but if you have symptoms like mine good chance its your HG
06-26-2012
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I have an 01 that is having the same problem. The head gasket was replaced and it still over heats just not as bad. Any suggestions?
08-05-2012
#26
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interesting - another member:
https://www.civicforums.com/forums/1...out-ideas.html
trick - check carefully for leaks in the radiator body too - could be it :P
the 2 miles to overheat was another clue - too fast to be gasket.
https://www.civicforums.com/forums/1...out-ideas.html
trick - check carefully for leaks in the radiator body too - could be it :P
the 2 miles to overheat was another clue - too fast to be gasket.
08-20-2012
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I have an over heating issue with my 2002 honda civic ex. Its overheated on me twice.
Ive changed the radiator cap and have noticed that my fans only work when im driving not when its is parked or stalled. ive also notcied that the radiator keeps sucking up all the coolant so im constantly added water.
Now what was really suprising is that i took off my bumper to check for any leakages or cracks but didnt find none until i opened the radiator cap and started adding water. What i notice is that as i was adding water to the radiator there was alot of fluid dripping from behind the motor kinda like when you bleed your radiator, the water just kept pouring out and the radiator wouldnt fill up all the way instead it would leak all the fluid out. Its really hard to tell where the leak was coming from because of all the parts surronding the motor. Can somebody help me out to find whats wrong with my car. Maybe some torn hoses? but its definitly leaking behind somewhere behind the motor?
Ive changed the radiator cap and have noticed that my fans only work when im driving not when its is parked or stalled. ive also notcied that the radiator keeps sucking up all the coolant so im constantly added water.
Now what was really suprising is that i took off my bumper to check for any leakages or cracks but didnt find none until i opened the radiator cap and started adding water. What i notice is that as i was adding water to the radiator there was alot of fluid dripping from behind the motor kinda like when you bleed your radiator, the water just kept pouring out and the radiator wouldnt fill up all the way instead it would leak all the fluid out. Its really hard to tell where the leak was coming from because of all the parts surronding the motor. Can somebody help me out to find whats wrong with my car. Maybe some torn hoses? but its definitly leaking behind somewhere behind the motor?
08-20-2012
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I have an over heating issue with my 2002 honda civic ex. Its overheated on me twice.
Ive changed the radiator cap and have noticed that my fans only work when im driving not when its is parked or stalled. ive also notcied that the radiator keeps sucking up all the coolant so im constantly added water.
Now what was really suprising is that i took off my bumper to check for any leakages or cracks but didnt find none until i opened the radiator cap and started adding water. What i notice is that as i was adding water to the radiator there was alot of fluid dripping from behind the motor kinda like when you bleed your radiator, the water just kept pouring out and the radiator wouldnt fill up all the way instead it would leak all the fluid out. Its really hard to tell where the leak was coming from because of all the parts surronding the motor. Can somebody help me out to find whats wrong with my car. Maybe some torn hoses? but its definitly leaking behind somewhere behind the motor?
Ive changed the radiator cap and have noticed that my fans only work when im driving not when its is parked or stalled. ive also notcied that the radiator keeps sucking up all the coolant so im constantly added water.
Now what was really suprising is that i took off my bumper to check for any leakages or cracks but didnt find none until i opened the radiator cap and started adding water. What i notice is that as i was adding water to the radiator there was alot of fluid dripping from behind the motor kinda like when you bleed your radiator, the water just kept pouring out and the radiator wouldnt fill up all the way instead it would leak all the fluid out. Its really hard to tell where the leak was coming from because of all the parts surronding the motor. Can somebody help me out to find whats wrong with my car. Maybe some torn hoses? but its definitly leaking behind somewhere behind the motor?
08-20-2012
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read thread first - you failed to read the first post, from starters
and double posted, so you not helping anyone. why should others help?
you did not read, so why should we assume you will actually read what we reply?
Note: all of the members that did not read but wanted to ask anyways received a bad rep for the simple act of asking without reading. what's the point? no reading, no meaning to reply... asking on internet means you will need to do diagnosis by yourself - i am not gonna leave my job to help you diagnose and fix your car...
you did not read, so why should we assume you will actually read what we reply?
Note: all of the members that did not read but wanted to ask anyways received a bad rep for the simple act of asking without reading. what's the point? no reading, no meaning to reply... asking on internet means you will need to do diagnosis by yourself - i am not gonna leave my job to help you diagnose and fix your car...
Last edited by sdaidoji; 08-20-2012 at 10:18 PM.
