I did a search and can't say I found a problem that duplicates mine. My Civic is a '92 CX, 5 sp. with 260,000 miles. My problem started about 400 miles ago when I noticed the temp. guage climbing, up to the red. I immediately turned the heater on and the temp. guage dropped to the normal range. I turned off the heater and then you could watch the guage slowly go from normal to near hot before going back down by itself. I arrived at home and checked all fluids and they were all up and normal. The radiator was not feeling hot and not burping. There was no evidence anywhere of any leaks. I thought that just maybe the thermostat was bad, so I replaced it and the antifreeze. For 2 weeks, all was normal. Then tonight it started doing it again. Again, a total search was done. Every fluid is at normal levels, normal color, the radiator fan came on when parked and then shut off, with the engine not running (as it should). I took apart the the electrical connection on the thermostat housing. cleaned the contacts and put a diaelectric grease on the connections. I did not take the ground wire off of the 'stat housing as it was of course removed and replaced when I replaced the 'stat, so I would think it would have a good ground. What could I be missing? The engine runs great. For the past 2 weeks, the temp. guage would climb to the normal range after about 2 miles +or- and then stay there like a rock. The only thing I noticed is that the little green arrow light that tells you when to shift, does not always come on. It may work about 1/2 the time and this started about 6 weeks ago. Any help?

 

Do you overheat only when driving? Or when sitting at idle? Or both?

 

I can't day I ever just let it sit and idle. But, yes I do to run into the Post Office or bank and it always normal when I return. I only have seen the guage climb when driving it. Tonight, I had went about 20 miles, when it started to do it. I was near home and my errand was over with anyhow, so I parked it and started checking things. The first time it did it weeks ago, it was after about a 15+mile drive. I live in a rural area, so in the small town near where I live, means I have one traffic light to contend with.

 

I had the same problem, but it was after I drove hard on a highway for an hour then sat in traffic because my cooling fan was not getting a signal, I replaced the relay switch to the fan.

Check your cooling fan by unplugging your thermostat, jump the two terminals with the key on and the fan should turn on if it doesn't it the fan, but also check the relay and switch.

 

If you are overheating while driving, when is the last time your water pump was changed?

 

Thanks for the responses. I hope(fingers crossed) I have it fixed using the advice I got here. I "thought" I had the radiator topped off after changing the thermostat. In what I read here, the talk of purging the cooling system could be needed. I had 1/2gal of anti-freeze here, so this morning I started in and out it all in the system and I still know I didn't completely top it off. I drove it to the parts store with a cautious eye on the temp. guage and it went to normal and stayed there the whole 25 mi. round trip. When it cools, I will top the radiator off. I don't know if it will take a cup or a quart, but it has to be close to full anyhow even now. I would have thought, in those 25 miles, that the guage would have showed a problem if there was one. There was about 15 min. of in town driving and the rest was 60+mph on the highway. Thanks all, I hope it is not a problem but my lack of attention in refilling the cooling system after changing the thermostat. Thanks again.

 

cvcrcr99, the water pump never was changed. On a curious note, being used to GM small block cars, the water pump is either not leaking from the seal and considered good or leaking and considered bad. Does a Honda water pump fail to pump?

 

IMO, it is a possibility. If no part of the cooling system is clogged and if your Tstat is not sticking shut, you should have no problems with cooling while driving. However, if the water pump is not pushing the water through the system, you will overheat.

 

I don't have an answer about the system being clogged. I did put a new radiator in about 6 yrs. ago. The plastic top tank in the radiator developed a crack so I replaced the radiator. I replaced the thermostat about 5 weeks ago or so. Of course, it wouldn't be the first time that I got a bad new part. I have learned long time ago, that brand new, doesn't ALWAYS mean that it is good, we all just assume it is good. Thanks again, love the responses.

It may explaing though several things, as I watched the temp. guage go up and down. One, is the water is being pushed by the water pump. Another is that the 'stat is opening and closing, since we see the guage move up and down. The air that was probably and even had to be in the system was not keeping the temp. sending unit in a constant enviroment to show a steady temperature. Either steadily increaseing, steadily decreasing or just plain holding steady. JMHO.