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I have an 01 civic coupe ex and there has been three separate incidents in which the car starts to overheat. The last two times that it has happened, as soon as i start going the gauge starts to drop. So im thinking that it might have something to do with the fans. I checked for leaks and didnt find any. I also checked the fuse and it hasnt gone out. I know someone who works for a honda dealership and he said it might be a faulty fan switch but he cant check my car out until next saturday and i kind of want to fix the problem already cause its been going on for over a month know. is there a test i could do at home and how hard would it be to replace it myself. Im not really an expert but with instructions im sure i could get the job done. Or should i just wait til he could look at it?

 
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Does your fan turn on and run when it's over heating?? If so then the fan switch isn't the problem. You said you checked for leaks and the fuse, did you check the coolant level too? If not, a system that wasn't toped off could stay cool under normal driving, when it wasn't being pushed hard, but would probably over heat at a stop. One more question. It seems that this always happens while your stopped. How long do you usually sit before it occurs? Does it always overheat if you sit and idle for that long?

 
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There are times that i hear when the fans are on. yes i checked the coolant level too and it was fine. usually i sit for like 4 mins and then it will start to overheat. It doesnt happen all the time that is why im thinking maybe there is a loose wire or something. Doesnt help out that i live in so cal and the temp is like 85 to 90 everyday that is why i want to fix it so im not always worried about it especially since im going to be going to school everyday and have to travel 30miles each way.

 
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im having a very similiar problem. with the same car.

on the hot days my car quickly heats up. the needle gets very close to the red while driving around the city or idling. it started about 2 weeks ago with some of the hot hot weather.

down the highway or interstate it stays at an optimal temp, and even gets lower when i turn the ac on.

i hear my fan turn on also, there are no leaks, and my coolant is topped off. could it use a flush?

to add right around the same time, my car started sounding louder. would a leak somewhere in the exhaust cause the temp to rise?

 
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slammin:
An exhaust leak will change the dynamics of the engine, causing it to run lean, or rich, which can cause the engine to create more heat. Reset the ecu, that should help some until you fix the leak, then reset it again.
Of course you still may have a different problem.
EDIT: Where is the exhaust leak? If it's near the header it could be shooting exhaust air right into the radiator.

dc:
I would suggest flushing the system. I'd probably go ahead and replace the thermostat while the coolant was out. It may be occasionally sticking, or only opening partially sometimes, something like that.

 
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im gonna get it on a lift this week to find it. i can hear it more towards the engine. it definitely runs a little funky since too. but noticeably losing fuel mileage.

also, would the leak possibly blow hot air onto the thermostat? or that wut you mean but shooting exhaust into the radiator?


thanks for the advice!

 
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Not quite, I was saying it could be pushing hot exhaust gas through the radiator, instead of cool out side air pulled in by the fan, which wouldn't help to cool the water any.

If the exhaust leak effected the thermostat (which it can't reach) it would cause your car to run cold, not hot, since the thermostat would always be opened.

 
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hmmm that makes a lot of sense! thanks.

 
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so i got it on a lift, after 1 guy trying to charge me 75 bucks to lift it! DOUCHE!

i parked it, waiting for another appointment. took it in last friday, no signs of exhaust damage, anywhere.

he said the newer civics can be really iffy when it comes to which coolant you choose. so he added some coolant directly to the radiator. it was the honda blue coolant. was like 28 bucks a gallon!

but she seems to be running like a dream, the temperature is running lower than ever. i also learned i will always spend the extra money for the honda coolant.

 
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That's where you were adding it and checking it too right??? Just making sure. Because the overflow tank can have fluid in it when the radiator is low.

 
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My 2003 civic ex is also overheating also. There has been several incidents where it would start overheating... I replaced the thermostat, and it ran fine for about a week, until it started to overheat again. Each time, I would blast the heat, and drive the car at least 40 mph+. Weird thing is, the car would stop overheating after awhile. I took it to my mechanic and he replaced the thermostat again, saying everything else is working fine. Now its starting to overheat again... weird but the overheating usually happens when it rains...

 
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perhaps you have exposed wires somewhere and the rain is shorting out the fan.

 
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originally i wasnt adding any to the radiator. i pretty much learned that from this whole incident

 
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Well, that's the cure, not the genuine Honda coolant, although I'm sure that at nearly $30 a gallon it's good stuff.

 
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Guys...I don't post a lot on this forum, but I use it a lot and good some info from my mechanic on this problem that might be useful.

My Story:

About 3 months ago, I noticed my car overheating. When I was running at 45+ on the open road, it ran fine, but would spike anytime I slowed down, get behind somebody, came to a stop, etc. Only did it when the A/C was off - diagnosis - bad radiator fan switch - tested and confirmed bad by my mechanic. Got switch replaced. A month later, starts happening again, exact same symptoms. Take it back to my mechanic and as any good mechanic should, replaces the switch no charge. Starts happening AGAIN! Take it back to my mechanic, looks over the car for like a day, baffled.

In between trip two and three, I was actually driving by his shop and it was overheating, I pulled into his lot, drug him outside, popped the hood and pointed at my cooling fan which was NOT RUNNING as the engine was running near red line. So he's had it for two days now. When he starts it up in the parking lot and lets it idle up to temperature, everything works PERFECT, fans and all. Finally came up with a creative diagnosis that I'm going to confirm myself this weekend (thanks to this fantastic forum and it's many DIYs):

When I drive to and from work, I hop in my car start, and leave - literally no stoplights and only 1 stop sign between my house and work - 20 minute drive. Car heats up very quickly - unlike when he lets it heat up in his parking lot. He believes that my head is warped and/or head gasket is damaged in between one of the cylinders letting exhaust/combustion gas leak into one of the cooling chanels pushing air into the system...once this air pressure makes it to the fan switch, the switch doesn't function. He suspects the warping/damage occured from the initial round of habitual overheating caused by the fan switch ACTUALLY being faulty.

Passes my smell test, what do you guys think?

 
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its possible, if you ran the car when temp was above normal, the head is prolly damaged.

 
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yeah. wouldnt you be able to tell if the head is damaged by a low coolant level?

or a bubbling in the radiator?

 
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yeah even a small leak would cause bubbles, or white smoke out exhaust, or white deposits on exhaust or spark plugs.

 
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ya this happened to my car and my head is now warped , what the he88 is going on but mine was after only 60k

 
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sorry i havent posted back but in my situation it turned out to be that i did have a blown head gasket and my head had been warped. i took it to a honda dearlership, where a buddy of mine works and he told me what it was. The company that is contracted my the dealership to machine the head actually messed it up so they had to buy me a new one. in the end i got it all done for $590 bucks which i hear is a very low price. Now it hasnt overheated, but there is another problem i have with it. i feel like im driving a ford, lol everytime i fix something, something else goes wrong.

 
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i was overheating but that was because somehow my coolant catch tank hose got clogged and it messed up my thermostat... so i made my own catch tank and got a new thermostat... never had problems since