Hey guys I need your expetise. I have a 97 Z28 and after a half mile of driving my temp gauge shoots up to 240 degress and the fan kicks on. But here is the problem. I have a 180 degree thermostat and when I check the temp of the coolant and hoses, the temp is 180. I know it is not the water pump, as I can see when the thermostat opens and the coolant circulates.
So the temp gauge reads 240, but actual temp is 180, but the fan kicks on because it reads the temp at 240.
What sensor do I change.
So the temp gauge reads 240, but actual temp is 180, but the fan kicks on because it reads the temp at 240.
What sensor do I change.
Registered User
sounds like either a bad sensor for the gauge, or an air pocket in the coolent system; did u purge the system of air via the 2 bleeders on the coolent lines near the tb?
Registered User
Try bleeding the cooling system this way: with the car cold and engine off, loosen both bleeder screws, remove the radiator cap, and fill the system. Allow the water level to go down and refill as necessary. When no more air bubbles come from the bleeder on the water outlet, tighten down the screw and proceed to do the same with the other bleeder.
Now, start the engine with the radiator cap off and allow to reach opperating temperature. The water level should go down once the thermostat opens. Open ONLY the bleeder on the water outlet and top off the radiator until it stays full. The water level should be high enough that when you put the radiator cap back on, it's going to be touching coolant.
Once the water level is stable, put the cap back on, tighten all the way. NOW loosen the bleeder on the small hose and wait for only coolant to come out of it, then tighten it up. Check the coolant level in the overflow reservoir and fill as necessary.
I've noticed that if you open the bleeder on the small hose while the radiator cap is off and the engine is running, it will cause the cooling system to overflow, spilling out enough water to cause problems.
Take the car for a short drive, come back, crack the radiator cap and refill (with no bleeders open) until the coolant level is stable again, then close the system, crack the small bleeder until only coolant comes out, and check the reservoir again.
Repeat as necessary.
I know this is far from the normal procedure, but it's worked for me time and time again.
Now, start the engine with the radiator cap off and allow to reach opperating temperature. The water level should go down once the thermostat opens. Open ONLY the bleeder on the water outlet and top off the radiator until it stays full. The water level should be high enough that when you put the radiator cap back on, it's going to be touching coolant.
Once the water level is stable, put the cap back on, tighten all the way. NOW loosen the bleeder on the small hose and wait for only coolant to come out of it, then tighten it up. Check the coolant level in the overflow reservoir and fill as necessary.
I've noticed that if you open the bleeder on the small hose while the radiator cap is off and the engine is running, it will cause the cooling system to overflow, spilling out enough water to cause problems.
Take the car for a short drive, come back, crack the radiator cap and refill (with no bleeders open) until the coolant level is stable again, then close the system, crack the small bleeder until only coolant comes out, and check the reservoir again.
Repeat as necessary.
I know this is far from the normal procedure, but it's worked for me time and time again.
Administrator
The gauge comes off one sensor in the head... and that's telling you the coolant is 240*. The fans are controlled by the PCM, using the sensor in the water pump housing, and that sensor is apparently telling the PCM the coolant is over 236* since both fans are on.
Wouldn't it seem odd that both these sensors happened to fail at the same time?
How did you determine the coolant is actually 180*? Where in the cooling system did you make that measurement? Measuring the temperature of the hoses is not going to indicate the temp of the coolant in the block, heads and water pump.
Wouldn't it seem odd that both these sensors happened to fail at the same time?
How did you determine the coolant is actually 180*? Where in the cooling system did you make that measurement? Measuring the temperature of the hoses is not going to indicate the temp of the coolant in the block, heads and water pump.