I have a 2001 Civic LX that started running hot about a month ago. I changed fan switch because fans were not coming on. Thought I had her fixed but NOOO. I then changed thermostat and relay for the fan switch just because the parts guy sold me on it and still HOT. I can drive the car for about 30-45 minutes with the temp guage at the normal spot, after the continuous driving the temp guage rises, and falls. I am thinking I got a faulty thermostat but would value yall input here. Yesterday after driving the 45 min the temp climbed so I stopped to make sure fan was on and it was the hoses were hot and had pressure........car has 150k miles and drives like it's brand new - love my civic but this problem is driving me crazy....

 

air in the system would cause the car to overheat at idle and go back to normal driving so burp the system. if that is the problem and there is air then you need to find out where its coming from and pray its not the head gaskit which was a problem for 01-05 civics. also make sure yor radiator cap is in one piece and functioning.

 

Just drove 3 hours on interstate with no real temp changes. After one hour of driving the temp needle moved 2-3 lines - no big deal. Right after I got off interstate temp rose to 3/4 high. After I got into air again back down to normal. The fans are blowing but could they not be blowing hard enough? Did pressure test and it was fine. Any thoughts ?

 

like i said before try to bleed the air out of the cooling system if there is any.