Accord 4cyl overheating...probably a leak or air in system

talontsiawd

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I have had never had cooling issues on any of my cars so this is new to me. A few months ago, my car would overheat in traffic so I replaced the thermostat. I didn't really think about this at the time, but I was really low on coolant. In the past, when I changed my thermostat (I have owned the car since 2003), I recall coolant coming out of the thermostat housing. The last time, no coolant and if I recall, no coolant really in the upper radiator hose when I refilled the coolant. At that point, if stuck in traffic, I could rev the engine a bit and temps went down to normal.

My car started overheating again, it was minor until today. Though I could rev the car to get my temps down, it didn't work well enough for me to get to school. I am a grad student with night classes so I didn't want to be stuck driving home at 10:00 PM so I went home. As soon as I got out of traffic, and could drive normally (with the heat up at first), temps remained normal. After my car cooled down, I found I needed to add about 1/3 gallon of water. Because I filled it about a month ago, I believe it is a leak.

What I have done before adding water. I let my car idle and get up to temp to see if my fans were working. They work fine. I then added water and my temps are fine. I went out and rented a pressure tester, it is now dark, I cannot find any obvious leaks, but the tester seamed to leak as what I heard was right at the cap area, but no coolant lost.

In addition...My car is daily driven but only has 90k on it, I don't drive much. A lot of times, if I drove a regular amount of miles, I feel I would detect these problems more easily, and also, they would likely be worse. I would not be surprised if adding more coolant (well water in this case), will be fine for 6 months or more.

What are your suggestions going forward? I have no reason to believe the coolant temp sensor is bad, but it is almost 20 years old. I do believe I was overheating because my car was running like it had no power, but no CEL came on. Still, I don't see any signs of a leak. I may be able to get a better pressure tester, or find something when it is more light out, but my garage is fairly well lit. I did smell coolant when it overheated, I don't recall that in the past when I last replaced the thermostat.

Long thread, I just need to deal with this, I understand how coolant systems work, I just haven't really worked on one, outside of my old Jaguar, outside of failed thermostats. Again, my lack of driving my car often makes me think I fixed something when I didn't.
 

Eclipse99fwb

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If your adding coolant or water, you have a leak. The coolant system is sealed meaning you shouldnt need to add. Now here some areas you need to check (if your coolant is mainly filled with water tgis is going to be harder, normally you can find dried coolant trails from the leak).

Check around your heater hoses going into the firewall. This may be easier with tge car running as it can be a pin hole leak.
Check around the thermostat, look for any signs of dried coolant.
Check all around your upper/ lower radiator hoses and the radiator.
If it is dry around these areas check around the bottom and back side of the timing cover, it may be the waterpump. Your due for the timing belt, balance belt and water pump at 90k.

Its going to be one of these areas 99% of the time. Also keep in mind if your system is filled witg mainly water your temp will increase quicker since water boils alot sooner than a 50/50 coolant mixture would.

The only other two possibilities would be a heater core leak (the carpet would be soaked around the glove box) or blown headgasket(not likely very uncommon on honda motors)

Hope tgis helps let me know if you need anything else.
Also check your radiator cap, make sure the spring/vent is still on tge bottom of the cap. These fail alot and come apart in tge radiator.
 

talontsiawd

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If your adding coolant or water, you have a leak. The coolant system is sealed meaning you shouldnt need to add. Now here some areas you need to check (if your coolant is mainly filled with water tgis is going to be harder, normally you can find dried coolant trails from the leak).

Check around your heater hoses going into the firewall. This may be easier with tge car running as it can be a pin hole leak.
Check around the thermostat, look for any signs of dried coolant.
Check all around your upper/ lower radiator hoses and the radiator.
If it is dry around these areas check around the bottom and back side of the timing cover, it may be the waterpump. Your due for the timing belt, balance belt and water pump at 90k.

Its going to be one of these areas 99% of the time. Also keep in mind if your system is filled witg mainly water your temp will increase quicker since water boils alot sooner than a 50/50 coolant mixture would.

The only other two possibilities would be a heater core leak (the carpet would be soaked around the glove box) or blown headgasket(not likely very uncommon on honda motors)

Hope tgis helps let me know if you need anything else.
Also check your radiator cap, make sure the spring/vent is still on tge bottom of the cap. These fail alot and come apart in tge radiator.
Thank you, I found the leak at the cooling outlet for the upper radiator pipe (where the plastic housing is). I just happened to have accidentally bought the gasket when I bought my thermostat, not I can't see any obvious cracks in the plastic but haven't taken it off yet.

I thank you for your thoroughness as the leak wasn't obvious, so I could rule other things out, then, it was much easier to spot.
 

Eclipse99fwb

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Glad you got it figured out. Keep a eye on everything once you get it fixed. I had bad luck after i replaced my radiator hoses and radiator. Both heater hoses went afterwards, fixing one part tends to make the next weak part to show.
 
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