Engine overheating

Thanks. It turned out to be the fan switch is bad. So I used a jump wire and fixed the problem. :-)

Engine Cooling problem
1995 Honda Civic Automatic 116000 miles

I have a 1995 Honda civic DX coupe with 116K miles on it. Bought it about 15K miles back last year. About a couple of months back, I had gone out of town. It was a hot summer day, so the AC was on and there was a lot of uphill driving. The engine started heating up. I let the car cool down, checked the radiator and the resrvoir and saw it was very low on coolant. So bought coolant (Zerex pre-diluted, which mentioned Honda as one of the brands it would work for) from a gas station, and topped up the radiator and the reservoir (to the MAX level). Drove back home (about 50 miles), and there was no problem.

After that, for the next 2 months or so, was driving only in town (I live in a small town, so even the longest drive is maybe 5-6 miles at a stretch). No problems with overheating or anything.

Then last weekend, I was on a long trip again. Another hot day. Was on the highway and it was fine. We didnt have the AC on, and the windows were rolled down. Took an exit for some coffee, and the temperature gauge started climbing up. Checked the coolant level and it was fine (in fact coolant in the reservoir was above the MAX mark). I noticed that the cooling fan wasnt working. So I assumed that was the problem. Let the car cool down, continued with my trip on the highway. The temperature was OK as long as I have driving at 55 and above.

But an hour later, when the traffic slowed down due to road work, the gauge started climbing again. Luckily, the traffic didnt last long, so we were back at high speed and the gauge went to below the midpoint. Whenever the car overheated, I would pop up the hood and the fan would usually not be working.

So I googled fan troubleshooting tips and found advice on several forums. Took the connector off, shorted the pins and the fan started running, so the fan motor was OK. One possible reason being mentioned was thermoswitch and/or thermostat being bad. It was mentioned on a couple of forums that I should check to see if the lower hose was cold. It was not. After keeping the car in idling for 10 minutes, both the upper and lower hoses were hot. The upper one was hotter, but the lower one was hot too. So I took this to mean that there probably wasnt a problem with the thermostat or thermoswitch.

Next, I read that air pockets could be stopping the fan from coming on, so I should purge the system. Did that. Fan came on twice while the car was in idling with the reservoir cap open. So I thought now that the fan was working, things were fine.

Took it for a test drive. Took an exit and slowed down after 45 mins of driving, and there we go again. The gauge started climbing up. Popped open the hood, and saw the the fan was actually working. Both the lower and upper hoses were warm (though like I said, the lower was was a bit less warmer). Yet the gauge kept creeping up. Drove back again, maintaining high speed and the temperature remained fine.

So here are my questions -

1. Is it still possible that something is wrong with the thermostat or thermoswitch? The fan is coming on now, and the lower hose is not cold. I read somewhere that if the thermostat is busted, the engine will pretty much start overheating in minutes, and won't cool down even if you are at high speeds. Dunno if this is right.
2. There are no visible leaks. The coolant level is fine. I dont see any leaks from the water-pump either, but could that be a problem?
3. In general, what else, apart from fan problems, could cause this intermittent at-low-speeds-only overheating? Wherever I saw people saying that they had this problem, the people responding invariably said it was a fan problem. But now that the problem is occuring despite my fan running, what else should I check?

I am taking the car to a mechanic today for a diagnostic check, but would also appreciate some inputs here in case he cant figure it out.

Thanks. Oh, and today I need to drive 4 hours to pick my mom up from the airport. I was wondering, if intermittent fan operation is the problem, is it advisable to jump the connector pins so that the fan will stay on all the time, as a temporary fix? Or will keeping the fan on all the time that I am driving, damage the fan?

Thanks.

Here is some brand new information from the trip to the mechanic. He noticed that the coolant level in the radiator was not up to the neck, although I had topped it off just yesterday (the reservoir level was good though). He added some more coolant and it took very little (maybe 2-3 ounces - 60-90 ml) to top it up. So it was not like the coolant had run out fully, but some of it had gone somewhere.

So he hoisted the running car up with a cardboard under it to see if there were any leaks. Kept it like that for over half an hour and not a drop of leak. He also checked the oil cap and the dipstick to see if there was any green or white coloration caused by the coolant leaking into the oil, and that didnt seem to be the problem either. He also looked at the exhaust to see if any white smoke was coming out, indicating the coolant going out through the exhaust, and that wasnt the case either.

He has asked me to leave the car with him for a day to test this further. Any idea where else the coolant could be going?

Engine Cooling problem
1995 Honda Civic 4 cyl Manual

would a not working cooling fan cause shift problems

What do you mean by clutch operation, it is an automatic test drove it Thurs, bought it Friday, drove home 40 minutes road great, parked overnight Sat drove it only 2 houses away to get gas, overheated immediately pulled over, radiator cooling fan was not on put in Reverse and it felt like it was in neutral, I know the fan could be the fuse or the motor, that's not that big a deal, but the transmission? It is an Automatic and when I bought it the guy said his mech. Said the throttle idled to high and it needed proper adjustment. Driving wise it went thru till, at 35rpm's it didn't wanna go until it was put into d3? Any help would be greatly appreciated?

Well, Just picked up from a service guy, the cooling fan is fine, just unplugged, on the drive home if I gave it light gas at 40 rpm it was fine, but if to much I had to go to d3 then no problem, got home, absolutely no reverse? My next thing is do I need to take to a tranny guy? I don't know where or how to check the gear box oil level. Thanks for you help so far

Engine Cooling problem
1995 Honda Civic 4 cyl Front Wheel Drive Automatic 140, 00 miles

Replaced thermostat, radiator and cap, upper and lower hoses, water pump, timing belt.

When idling, temperature remains normal, cooling fans come on/off. After a couple of days of driving, loss of coolant, overheats, pressure builds in radiator. Had block checked for blown head-gasket. Checks out ok at this time, no hydrocarbons in cooling system.

Please help with advice. Thank you

Yes, the air was properly bled. When it overheats it blows back into reservoir. No coolant leaks to be seen. No recent pressure test.