My sister have a 94 civic DX.
Recently it started to overheat, so i added more coolant to the radiator.
It stopped, now its doing it again, and more often.
I checked and confirmed i do not have any leaks anywhere.
I noticed that when the car is overheating, you know the bottle where the extra water resides with the hose comming from the radiator, the water in that bottle gets so hot that there are bobbles popping in it.

oh and the car is completly stock.

 

bad thermostat maybe. Is the air compressor hose firm when the car gets warmed up? If not the thermo needs to be replaced. do you hear the compressor coming on at all?


[Modified by maxim, 12:33 AM 7/4/2002]

 

When the car overheats, everything is normal, the pipes don't swell up or anything. But that bottle heats up with hot boiling coliant in it.

 

Ok dunno if you know what a thermostat is; basically it is a valve that opens and closes relative to temperature of the coolant. This is to regulate flow of coolant in the engine. The t-stat is a wear item and can need replacement from time to time.

An easy check of thermostat failure: (Once your engine is running and you can see the temp needle climbing -- which is a very bad sign)

The hose entering the radiator (top hose) will be quite hot but the hose exiting will be cold(er) -- more like warm. If both hoses are equally hot (in which case they will be very hot) then it's probably not the thermostat. I hope that makes sense.

 

ok, so i drive the car around, bring it to normal operating temp. or let it overheat for a bit, than kill it, and check to see if the bottom radiator hose is hot or not.

If its hot than its not the thermostat.
if its cold that its a bad thermostat.

am i correct.

 

Well, like I said if the hose is not firm then your thermostat is not working properly. I doubt it is the water pump, but it could be. You should be able to hear the compressor turn on and off. If it is not clicking on and off the water pump is not turning on because the thermo is stuck or is just not working. Hopefully it is just the thermo because those things are not expensive. The water pump on the other hand

 

have you check your fan too see if it is coming on when the car is overheating?? if not i would check the fan motor by just jump the wires that come from the fan to the battery and if it comes on it's OK, and check the thermo switch it is on the thermostat housing. pull the wire plug from the switch and jump the connector and the fan should come on.

Hope that helps

 

I don't think it is the fan. Most of the time it is the thermo.

 

i don't think its the fan either, but why would the colant boil in that bottle ??

 

The coolant is pumped out the block and into the radiator then out the radiator back into the block. Before re-entering the block, it has to pass the thermostat (the thermoswitch is housed nearby as has been mentioned). If the thermostat is jammed, most of the hot coolant never exits the radiator since the flow is blocked.

The engine gets very hot and all the coolant in the upper tube entering the radiator gets very very hot. When the pressure of the system is exceeded, it's usually released as steam/fluid through the radiator cap. The coolant stored in the reservoir (the bottle) is then drawn in by pressure. Since the coolant in the bottle is part of the cooling system, the heat is also conducted there and the coolant in there boils as well (I think I'm forgetting something here but that's all that's important).

The thing to remember: if the thermostat is blocked, the temperature of the coolant in the lower hose (exiting the radiator) will not be near the temperature of the upper hose. This means the thermoswitch will not turn on the fan. Usually the fan isn't the problem with an overheating car except in heavy traffic. The volume of air the fan can draw in is really not very much compared to the volume of air displaced by a moving car.

It's probably the thermostat, like someone else mentioned. No big fuss.

 

Exact same thing just happened to my civic. It was overheating and the coolant overflow bottle kept filling up. I replaced the t-stat, radiator cap, and flushed the coolant. Nothing seemed to help though. I decided to pull the head off. When I got the head off, there were no visible cracks or blown out spots. I put a new gasket in and it has been fine for over a week now, and the temp around here is in the high 90s. It very well may be your head gasket.

 

Update:

I just filled up the radiator with coolant and water, then took the car for a test drive, and noticed that the radiator fan is not working at all. How do i wire it up directly to the batter, so i'll know if the motor is not bad. i don't know much about electrical things.

Can someone guide me.

 

I just had this problem. It turned out to be my cooling fan motor had gotten crappy and didn't like to always come on. Solution: replace fan motor.

 

whats what i think too.

I need to hook up the fan with the battery to see if the fan is bad or not, but don't know how to do it.

 

 

i had the same problem... i replaced my radiator cap... im almost certain its your rad cap. if not the radiator cap then its prolly the thermoswitch... both are very cheap to replace and easy to install. if your upper radiator hose is hot, most likely its not your t-stat.

 

My RAIDATOR FAN was not turning at all. Could that be related to radiator cap.

 

well to test the fan motor just look at the back of the fan, there should be 2 wire coming out of it and that goes to a wire plug. Unplug that and take 2 wire that is long enough to go to the battery and strip the end of it, and just jam the strip end of the wires and put it into the connectors and run that to the battery one postive and one ground.

if the fan works then it is probably your thermo switch. That is locate on the thermostat. in the mean time to get a temp fix on it until you get a new part you could unplug the wire harness that connects to the thermo switch and jump the connectors, again just take the stripped wire and plug it into the end of the wire into one side of the plug and the other end of the wire into the other side. Does that make sense?? the wire should just make like a "U, one end of the plug directly into the other end... this will work fine until you get a new thermo switch.

Hope that helps

 

thank you

 

Also, check if your heater is working. If you turn on the heater, does it get hot inside the cabin? Or does it stay somewhat cooler? That means hot coolant is not getting to your heater core, and you may have bubbles in the cooling system, and a possible leak in the upper part of the radiator.

 

Hey I just moved from wisconsin to alabama went from mid 60's on a hot day to mid 90's on a hot day ... First time driving to work i glanced down and watched my temp guage moving up up so naturly I turned my heater on ..and it jumped back to normal running temp. well try driving around in 90 degree weather with your heater on .. Not fun trust me turned out my problem wasent the thermostat coolent or any thing else (checked all those .. even tried running water+watter wetter) I had a blocked radiator ... UP GRADE TIME ... i went with a fluidyne radiator and it has been running beautifuly ever sence !!! true story

NS

 

how can you tell if you have a blocked radiator?

today my CRX threw a code 1(first time ever) and it overheated a couple of minutes later(first time also).. white smoke was coming from/below the timing belt?? and some from a screw on the valve cover... Any help? I posted this in the EF forum but nobody replied



[Modified by crXtreme, 11:09 AM 7/5/2002]

 

You have a blown head gasket...

 

BINGO!!!