Originally Posted by sdaidoji

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...

Originally Posted by arizaga8799

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.

Originally Posted by Matt_75

Just for reference and I am in the process of changing the HG. Didn't even bother looking at thermostat, radiator cap or water pump. They were replaced about a year ago as preventative maintenance by me along with timing belt and associated items.

2002 civic ex with 85K
-No overheating
-Coolant spewed from reserve tank on trans and trans side of engine
-Reserve tank filled to the top and having bubbles coming up every few seconds immediately after shut down
-Waited 10 minutes and opened radiator cap. Air blew out and no coolant.

Originally Posted by sdaidoji

arizaga, thanks for the run down on yours too
hope you get yours figured out too.

Originally Posted by cpbennett

Wish I saw this thread when I was having issues a few weeks back!

Here is a case study for you guys (and girls):

2004 Honda Civic EX Coupe
Fiji Blue
130,000 miles

Issue:

First Day
-First time using my heater this fall on the way to work
-Noticed that when I slowed below 20mph, my car blew COLD air -- BBRRRR
-Fans were running, coolant level was ok

Second DAY
-Overheated (didnt actually overheat, just started getting too warm for comfort ~ temp guage inching towards 3/4) == SHUT CAR OFF RIGHT AWAY
-reservoir was filled to the cap- eek
-Let my car set for 2-3 hours
-Turned my car on, with rad cap off, no air...
-After car reached operating temp, a few bubbles came up, nothing crazy


Solution:

Drove my car to the STEALERSHIP due to panic that my heater core or HG had gone...F.

Paid them $85 to "look" for the problem. They lifted my car and some air came up - "burping" the coolant. The mechanical they lift the car due to the position of the radiator in relation to the rest of the system. Next, they pressurized the system and checked for leaks. They found NONE, thank GAWD. I told them about 20,000 miles back I paid a local shop to replace my timing belt and water pump, at a cost savings to me (I too am no mechanic). They mentioned that the other shop may have put the water pump in w/o bleeding the coolant system. I had this same problem last year around this time and it just needed more coolant and the same "burp". The other shop tried to convince me last year my radiator was leaking, which the STEALERSHIP confirmed was NOT THE CASE. He said to keep a close eye on the temp guage and went ahead and flushed / replaced the fluid.

I am hoping that last year they simply did not get all the air out of the system AND I hope my water pump hasnt been damaged due to cavitation.

LESSONS LEARNED:
The issues I had were caused by AIR in the system. That air, as the above members have mentioned, can get into the system multiple ways. All you can do is hope that it is one of the cheaper fixes.

I am worried that the air may have gotten into the system another way, i.e. the replaced water pump 20k ago wasnt the ROOT CAUSE of the issue.

MY QUESTION TO YOU?

Do you think I should worry about the Rad Cap, Thermostat, or WORSE the HG? Should I replace the Thermostat and Rad Cap just in case?



~~ ONLY USE *OEM* RAD CAP, THERMOSTAT, COOLANT ~~ NOTED.

Originally Posted by sdaidoji

if it's cheap, do them and thanks fer the input

Originally Posted by Matt_75

Once again for reference my findings from the above symptoms. It looks like #3 cylinder is the culprit from the discoloration.

Originally Posted by thiggins20

but if your oil doesnt look "watery" or hazy, and Dark smoke isnt coming out the exhaust,

Originally Posted by Stock 99

Lol, I think the Toyota 22RE was the nastiest engine I've dealt with. The timing chain could break the plastic guides and then chew through the water jacket milkshaking the oil.

Honda actually has a good design there if it was done on purpose. No milkshaking saves a lot of engine damage and it's easy to see your reservoir puking out fluid.

My '78 Civic used to run just fine until I shut it off and about 60 seconds later it would violently blow about a liter of coolant out the reservoir. I used to try and get as far away from it as I could before it puked so people didn't realize it was my car, lol

Originally Posted by dave9

2003 civic 1.7.... new rebuilt engine , new hoses, thermostat and pressure cap from honda..replaced radiator and still i have pressure build up that pushes coolant out usually out on passenger side lower hose.. and the car looses its coolant and over heats.... i am at my wits end trying to find the cause of the pressure buildup.... has anyone have any thoughts on this?

Originally Posted by dave9

2003 civic 1.7.... new rebuilt engine , new hoses, thermostat and pressure cap from honda..replaced radiator and still i have pressure build up that pushes coolant out usually out on passenger side lower hose.. and the car looses its coolant and over heats.... i am at my wits end trying to find the cause of the pressure buildup.... has anyone have any thoughts on this?

Originally Posted by Tim1959

Following is a useful summary of my recent experience with a 2002 Honda Civic LX, auto trans, 1.7-liter engine with 185,000 miles:

Originally Posted by AccidentProne

First off would like to thank everyone who posted all the awesome information on this thread. 8 years later and this information is still reaching members of this community. I am a new member so i apologize if im posting on this thread incorrectly.

But my reason for posting is here because it is 2019 and i was having much trouble diagnosing a bad head gasket on an 05 honda civic dx. Thanks to this thread i feel more certain i have a failing HG so now i can move forward to the next step and replace it. I Will be starting a new thread that will address all the issues i encounter diagnosing the problem as well as my progress update.

So of any veteran members have any advice for me before i post to an incorrect category or thread, please feel free to let me know. I want to respect the forums and rules.