My son bought a 2000 Civic from a friend. It has had some problems running hot. I replaced the timing belt (tensioner pulley chattering) and the thermostat after we got it home, because it was still running a little hot. The car had some overheating problems about a year ago and the radiator was replaced and some engine work was done to repair the damage. I guess the head has been resurfaced. I assume that the water pump was replaced then, as it should have been. When it is idling, and the thermostat is open I can see good coolant circulation.

When I replaced the thermostat and the timing belt I test drove it and I could not make the thing overheat. It was about 98 outside and I drove in stop and go traffic around town. The fan was kicking cycling at the right times and everything was fine. My son commutes about 45 miles to his classes, and that is when he says the temp gauge creeps up past the halfway mark. The check engine light came on a couple of weeks ago, and my scanner said that the engine was running lean in bank 1 and 2. I could not find any vacuum leaks. I erased the code and wondered if the engine running lean could cause it to run hot. Meanwhile my son drove it some more and it was running hotter that normal. The check engine light was on again. This time it is P0420. I pulled the freeze frame data:

Throttle position 16%
Engine RPM 1969
Load value 41.1%
Map sensor 42 kpa (we are at sea level)
coolant 258 degrees
intake air temp. 123 degrees
short term fuel trim 1.5%
long term fuel trim1 -4.6%
short term fuel trim3 -100.6%
long term fuel trim3 -100.6%
vehicle speed 47 mph
fuel system 1 closed
fuel system 2 n/a

Sorry about the novel, but I want to figure this out. I typed this data out exactly the way the scan tool displayed it. Thanks.

 

ok my friend i just had a problem with my cooling, the thing is i had air in the system, so what ya do is squeeze the hose a couple times that goes to the head while you pore coolant back into the rad. untill no more bubbles will come out and that should fix your issue, it will get to a point that when you think the rad is full just squeeze the hose and watch for bubbles to come out and then fill it back up

 

I called in to a radio talk show that features an expert mechanic. I described the problem and since the car only seems to heat up when my son drives it down the highway, he suggested it might be a leaking head gasket, causing air to enter the cooling system. What's funny is that I went outside, started the car and started squeezing on the hoses to see if the thermostat was opening. I had the radiator cap off while I did this. I then drove the car 40 miles, and the temp gauge never budged from the middle reading. So, I did what you suggested without knowing better, and it seems to have worked. Thanks for the advice, but I still won't relax until my son drives it out of town and reports that it is fine.

 

no problem my friend, glad i could help