When I drive my Honda on the highway and get off to drive reg-streets it starts to overheat slowly. I had a broken fan and it has been replaced also the ECT sensor was also replaced. It only starts to overheat if I have been driving on the Hwy for 25 miles or more then get off onto the reg streets. If i just drive it on reg streets nothing happens no overheating. I'm going to flush the raidator and test my thermotat in the mean time. Is there anything else I should be checking that I might have missed??

 

It's possible your water pump could be worn. You need to keep track if both fans are running(or if you don't have ac, if the one fan is running when it starts trying to overheat).

 

Both fans are running and yes I do have AC. Also I've tested and had to replace the fan for AC. I'll check the water pump do you lose coolent when water pump is bad? And if so is it a lot or a little at a time?

 

It will leak a little through the seep hold in the middle but that's when the bearing starts to go bad I think. The fins may start going bad before that happens if you use tap water instead of 50/50 coolant as tap water will corrode the fins away.

 

I've always used 50/50 mix I live in California so it gets very hot 107 ish it is on the really hot days that this problem seem to happen. On cool days it is not even a problem that's why I was thinking a coolent flush might solve the problem.

 

My car occasionally, on very hot days, will do something similar to yours. I have found that if I switch off the AC the temp will lower a lot. I had this same problem on another car that I converted from R12 to R134a. I believe the R134a generates a lot more heat and since the condenser is located if front of the radiator the air available to cool the radiator is a great deal hotter, thus less effective. As I said, this happens only when the temp is in the high 90's. All other times no problem. You might try switching off the AC and see what happens. I have heard that the first Hondas to use R134a were not all that efficient in the conversion. I believer that '93 and earlier were R12?

 

Well I've had this Honda for about 3 years and this has never happened on really hot days till now. So I tested a theory.... Before I got off the freeway I turned off my AC and slowly decreased my speed and coasted on the off ramp this seemed to help a great deal because it didn't over heat not even a flinch on the temp needle... So I'm thinking the thermostat might be reacting slower or maybe even a faulty coolent sensor.. Not sure will repost updates.