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Hi all.

2005 Civic LX 1.7 Auto

been experiencing over heating problem. Usually only occurs after long drives, and starts to overheat when slowing down or at an idle. If I throttled up to about 3K RPM, it would cool down.

I replaced thermostat, flushed, and water pump was replaced right at a year ago along with the timing component kit.

I’ve owned the car since 2015, and I’ve never replaced the radiator, so far I’m leaning in this direction.

my issue now has gotten so bad that after driving roughly 3-5 miles, it goes through the roof and I have to kill it.
I noticed when Overheating, the upper hose was hot, but the lower hose was cool, and no pressure on it. This made me think bad thermostat. However, I took the thermostat completely out last night. This morning I let the car idle for 30 minutes, did fine, and after 3 miles, started over heating again.

so here we are. I’m leaning towards radiator, which I plan on testing today by a water hose, or a faulty water pump, which has a lifetime warranty.

thoughts? I’m lost.

 
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Are the fans coming on?

 
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Yes both fans are working, but I think they only come on when the AC button is turned on.

 
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Well then I would say no they are not working properly if they only come on when a/c is on. You have to check that stuff and report back. Do you have a obd tool you can look at live data to check water temp? They are cheap pick one up. Look for the fans to run without a/c. I forgot the temp they come on but I believe my 2012 fans are running by 200f. You could also have a intermittent fan problem who knows but you have to rule it out to know for sure its not a fan issue.

 
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I do see your point, and will be checking this as well. 1 of the fans I have replaced a while back as well.

what do you say to the fact that the upper hose was hot and the lower hose was cold?

 
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Another thing....hows your coolant levels?
Is any coming out our coolant tank?
Any leaks anywhere?
Do you get much burn off out your tail pipe?

 
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Coolant levels seem to drop a little, but not a lot.

seemed like a slow leak at first. Performed pressure test, and had a small leak on upper hose. Resolved issue, performed another pressure test, and was holding strong after test at 15 PSI.

last night I opened the cap, and tried to add water, and it was boiling and spitting out when I was trying to add water. This was leading me to believe thermostat was stuck, so I removed it after the fact. Even after doing this, and loosing water, I might have gotten half gallon or less.

 
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Well that by itself right there I would question if the t-stat was opening or not but you already said you replaced it. The t-stat has to open and let the hot coolant flow to the radiator so it can be cooled but not sure if thats happening cause your hose is not getting hot and the car is overheating.

 
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Correct, and I have the same situation with NO thermostat at all.

this led me to believe radiator clogged, bad water pump, even though it’s only. A year old, or blown head gasket.

 
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If the t-stat is fine then theres got to be some kind of blockage in there. Coolant isnt allowed to be circulated which is why its over heating (unless fans so check them)
Sounds like theres alot to recheck and go over. At this point who knows about the water pump also. Just because its newish doesnt mean it wont fail.
Yikes, its times like this being a car guy comes with headaches LOL.

 
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headache does not even begin to describe my pain! Lol

my next question, is blockage in the radiator or the block?

tonight... going to attempt to pull upper hose off T-Stat, shove a water hose up it, pull lower hose off block, and check the flow. If this is good, I will flush the block. Afterwards, run for 30 minutes and check levels and attempt to remove all air, and see what happens.

I’m hoping I just find blockage in the radiator, and it stops there.

 
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My guess is you have a failed impeller on your waterpump. You mentioned that it was replaced about a year ago.

How well does the heater work?

 
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thought crossed my mind.
yes tensioner broke on timing belt under a year ago, I replaced the whole kit which included water pump. It is under warranty if I have to go that route.

heat works great!

 
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Update!!

i wanted to change our radiator last night, but opted to wait until the weekend for more time.

so instead, I pulled upper and lower hoses, flushed out the radiator forward and reverse for probably 5-10 mins each way, and the same thing with the block. Put hoses back on, filled up, worked out air, and worked perfect.

as water was heating up and working bubbles out there were little pieces of trash floating up to the top of the radiator. So I’m sure it’s clogged, but at least I got a temporary fix until the weekend.

 
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Another update - I replaced the radiator last weekend. Was doing ok until this weekend. Tried to make a 60 mile drive, and before half way in it started over heating on me.

pressure test shows no leaks at 15PSI.

with pressure tester on, at 0, just turning the car over attempting to start it, builds pressure in the radiator up to 10PSI which I thought was weird.

compression test on all 4 cylinders yields 180-190 so good there.

after running hot, parking, pooping the cap, it had trouble starting back up, which I was guessing was water in the cylinder at this point. After finally starting, water shot out of the radiator.

I also have water dripping out of the tail pipe. Obviously not a good sign.

Pulled valve cover, and had a lot of water and oil mix on the top of it on the inside. Eww..

attepted torquing down the head bolts to about 60 PSI instead of the recommended 49PSI, out a new valve cover gasket on, and she did the same thing.

also, a lot of small air bubbles keep coming up in the radiator while running. Still water coming out of the tail pipe.

so basically I’m thinking gotta be blown head gasket at this point. I see nothing left to do but order new head gasket and head bolts at this point. Everything else such as fans, radiator, thermostat, water pump, timing belt, tensioner, etc are all new.

 
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That's what it sounds like. Head bolts do not need replaced unless damaged. You will want to take the head to a machine shop to be checked for warpage.

 
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There ya go. It happened on my 02 civic. I bought the car with about 117k on it and the head gasket was slightly blown but I didnt know it at the time. The car never over heated but on hot days coolant would get pushed out the over flow. Also I would notice the heat wasnt working at idle in winter. I drove the car like that until I realized it needed a gasket at 154k. Did the job myself and traded it in at 199k for 500 bucks. It was my beater car lol.

I reused the old head bolts, you can use them they are not torque to yield like other cars. Getting the head resurfaced is a must. Mine was pretty bad.

 
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update - spend pretty much the whole day today doing the job.

cleaned head, intake, exhaust, etc.
straight edge and feeler gauge showed about 0.006 of an inch only in the middle. Everywhere else on head, and block, was solid. Hung yo head gasket, and sprayed it thick with copper gasket spray. Coated block, head, and gasket thick with STP oil treatment.

Put her back together, Torqued everything to spec in sequence, then torqued an extra 5-10 LBS a piece.

she’s running better than she ever has. No more air bubbles in radiator, no more water coming from tail pipe. Made a 30 mile round trip drive no problem.

however, when I barely touch the throttle, it tried to jump a little high. It will jump up about 2k. After sitting still and idling for a minute, it will come back down around 1k (still seems a little high. While driving about 30MPH, I let go of gas, and it pretty much drove itself.

so seems like it’s sticking somewhere, and kinda jumps up and down too.

not sure if I got throttle cable back on wrong, bad sensor, dirty somewhere, etc.

 
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Check over everything, make sure you didn't miss a hose or leave a bolt loose. I would guess a small vacuum leak at this point. You can test this by removing the intake air filter box, start the car, use two fingers to cover the IACV port inside the throttle body. If the engine keeps running you have a vacuum leak. There are also lots of other suggestions in thread below, read it and start some testing.

https://www.civicforums.com/forums/3...e-posting.html

 
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everything is looking good. No cracks or loose hoses. Everything plugged in. I ran codes and got P0113 - IAT (intake air temperature) sensor or air charge temperature. Previously there was oil and water getting inside i take before this job. So it’s possibly the sensor went bad, just not sure why it wasn’t doing it before this job.

sensor is $20 so I might just go replace it.

thoughts?

 
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I would recommend an OEM sensor, not a cheap one from a parts store. A cheaper alternative is to get a used one from a junkyard.

You should be able to check the temp sensor as it's just a thermistor. If you have a scan tool read the IAT from the PCM, if the engine is cold it should read around ambient. If not unplug the sensor and jump the two wires together. Read the IAT again, should now be less than -4F (-20C). If not replace the sensor.

 
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got it! I will try this.

I will note - when sitting at a stop light, or at idle, it idles around 800. When I hear the 2nd fan kick in for radiator, I notice the idle go up to about 1100-1200 for a couple seconds, then drop back down. Don’t know if this is any help

 
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After cruising down highway, if I drop into neutral, it wants to stick around the 2000RPM point, after about 5-10 seconds it will drop back down to normal.

if at a stop or neutral, and I tap on the gas, it will drop down, jump itself back up about 2k, hold for a second, then fall back down again all by itself

 
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Took a video, won’t let me attach it. Anyone that wants to see I could email the video if necessary.

 
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Sounds like a vacuum leak to me.

 
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Everything may look good but it sounds like a vacuum leak. I would be under the hood spraying around the intake, hoses, anything that could be sucking in air. I have a mechanics stethoscope I would be using also.

 
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Update - just replaced the IAT Sensor, and no luck. Still having weird idle issues.

however, I found that upon unplugging the Engine Coolant Temperature (ECT) sensor, it goes nuts, and starts revving up and down all by itself. Could this be the issue? Wires from it run in line with the main wires on top of engine that run across the coil packs. 2 leads coming off of the sensor.