98 Cavalier - Engine is remaining hot

ewilson · #1 08-31-2005, 11:27 PM

Please I need some help. The Temp gauge doesn't always work. I have noticed that sometimes it will be working just fine then all of a sudden it will flop around between 100 and 195. Then it will stay below the 100 line. Also, the coolant is not circulating throughout the car. The hose to the radiator is cool while the hose after where the thermostat is located is extremely hot. I have already changed the thermostat twice. I just replace a sensor (one of two I guess) and the water pump has just been replaced. I am at a loss of what might be causing these problems. If anyone can understand what I have just tried to explain, and can help me I would be most appreciative!

jakegday · #2 08-31-2005, 11:29 PM

at first was gonna say THERMOSTAT but then i finished reading your thread, whens the last time youve had your cooling system flushed?? not just the radiator, but everywhere the coolant goes???
also something you might wanna try just for shits and giggles, try taking the thermostat out and see if that changed anything

ewilson · #3 08-31-2005, 11:35 PM

Currently the person who is trying to fix it, is running it without the thermostat and says that it is running fine. Also, we drained the coolant and running water through it. I'm not sure if that would be considered flushing the system out.

ewilson · #4 09-01-2005, 06:50 AM

UPDATE- my car is not holding pressure. Could it be the head gasket, or is there something else that we are missing? Someone please help I'm starting to lose my mind!

cdru · #5 09-01-2005, 11:30 AM

Are your coolant levels changing, either rising or falling? When my 98 Trans Sport's head gasket went, it would force a large pocket of air into the cooling system. This would work it's way to the thermostat and cause very quick fluctuations from normal engine temps to near the redline. Revving the engine slightly would push the buble past the sensor and the temp would return. Right before my head gasket failed completely, large amounts of air were being pushed into the cooling system. The air would displace the coolant into the resevoir, causing it to basically overflow.

I can't tell you what your Cavalier would do when the head gasket goes, but the coolant level will either rise (air displacing coolant) or fall (leaking externally or internally) if that was the case.

ewilson · #6 09-01-2005, 01:03 PM

The coolant levels seem to be maintaining. Out of all of this I do know that I am not losing any fluids. There are no puddles under the car, the oil looks good, and there is no smoke coming from my tailpipe.

Tookie · #7 09-01-2005, 04:21 PM

It sounds like your mech failed to purge all the air from the system during the last flush and fill. This is easlily rectified by running the car to temp where the thermostat opens and then adding the coolant that I hope you mixed to meet specs. Just for the record; did the mech reinstall the drive belt correctly; and are you sure the pump is known good?
My bets lay on purging and refilling the system; sans air. You can even reuse the coolant.

jwest30531 · #8 09-03-2005, 08:37 PM

out of curiosity... Does your cooling fan come on? at all? An easy oversight if one assumes it is working like it should. Even if it is working properly, try straight wiring it to a hot wire coming from your fuse box so that it turns on and off with the rest of car as you turn your key on and off; constant rotation will help keep it from getting hot instead of waiting for it to get hot before it comes on.

quake61 · #9 09-04-2005, 08:19 PM

Quote:

Originally Posted by cdru

Are your coolant levels changing, either rising or falling? When my 98 Trans Sport's head gasket went, it would force a large pocket of air into the cooling system. This would work it's way to the thermostat and cause very quick fluctuations from normal engine temps to near the redline. Revving the engine slightly would push the buble past the sensor and the temp would return. Right before my head gasket failed completely, large amounts of air were being pushed into the cooling system. The air would displace the coolant into the resevoir, causing it to basically overflow.

I can't tell you what your Cavalier would do when the head gasket goes, but the coolant level will either rise (air displacing coolant) or fall (leaking externally or internally) if that was the case.

well u also have to keep in mind this cars cooling system works under pressure if u loose pressure (steam) it wont matter if ur system is full of coolant

the car will overheat because the fan cools the steam not the water

if the coolant doesnt become steam car will remain hot

ewilson · #10 09-08-2005, 08:49 AM

The probelm has been found and fixed. It was a wiring problem. The plug that fits into the sensor wasn't working. The wires that went to the plug were broken, in some spots not even there. So, after spending money on a sensor, 2 thermostats, and a water pump it was the plug that cost $11. Thanks for all your input.

cdru · #11 09-08-2005, 09:26 AM

Quote:

Originally Posted by quake61

well u also have to keep in mind this cars cooling system works under pressure if u loose pressure (steam) it wont matter if ur system is full of coolant

the car will overheat because the fan cools the steam not the water

if the coolant doesnt become steam car will remain hot

That makes absolutely no sense. There is no steam in your cooling system...not if it's working correctly. Normal water boils around 212 degrees. A 50/50 mixture of ethylene glycol and water will push the boil point to about 225 degrees. Dex-cool antifreeze may be a little different, but for the sake of this discussion, presume it's the same as ethylene glycol. These numbers are for an open system, such as if you had the radiator cap off.

My '97 Cavalier uses a 15psi radiator cap. It will hold 15lbs of pressure in the system before venting to the overflow tank. Each psi adds approximately 3 degrees to the boiling point. So a 15psi cap would add an additional 45 degrees of boilover protection. So that 225 boil point is now around 270 degrees.

Unless there is something seriously wrong with your cooling system or you are in some seriously harsh driving conditions (driving up a mountain hauling a trailer in 100 degree weather), your coolant really shouldn't get to 270 degrees.

Coolant is pumped through the engine block by the water pump. There, it absorbs heat from the engine (heat "flows" from hot to cold). Because the system is closed and allowed to build pressure, the coolant doesn't have the ability to boil. From the block, some will travel to the heater core for your cabin vents before rejoining the rest of the coolant going to the radiator. At the radiator, the coolant is cooled by passing air across the radiator fins. Again, since the air is cooler then the coolant, heat travels from hot to cold. The cooled coolant is then sucked/pumped back into the engine block by water pump.

Of course if you run your car up to temperature and then open the system, steam will come out. This is because you have released the pressure, causing a rapid drop of the boiling point.

Steam is a poor conductor of heat compared to a liquid. You don't want any gas (meaning air or steam, not fuel) in your cooling system as it can create hot spots where the engine can quickly overheat as there is no flow of cooler coolant to absorb the heat. Also, an large air bubble in the system can cause what's called an air lock. The bubble may become trapped in a high spot not allowing any coolant to flow through that particular passage. It use to be that in most cars the highest spot in the system was the radiator cap, so an air lock wasn't as much of an issue. Many cars these days have one or more bleeder screws to allow air trapped in the high spots of the system to be bled out, preventing a air lock.

I don't know who told you your misinformation about your cooling system working on steam, but it's incorrect.

manny man · #12 09-13-2005, 10:12 PM

Quote:

Originally Posted by ewilson

Please I need some help. The Temp gauge doesn't always work. I have noticed that sometimes it will be working just fine then all of a sudden it will flop around between 100 and 195. Then it will stay below the 100 line. Also, the coolant is not circulating throughout the car. The hose to the radiator is cool while the hose after where the thermostat is located is extremely hot. I have already changed the thermostat twice. I just replace a sensor (one of two I guess) and the water pump has just been replaced. I am at a loss of what might be causing these problems. If anyone can understand what I have just tried to explain, and can help me I would be most appreciative!

manny man: How long does it take before your fan comes on?

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