Overheating Diagnostics - Continued...

[Mitch90535im]

Decided to start a new thread on this one -

Replaced the fan clutch ("borrowed" the tool from Autozone to hold the waterpump pulley)

Now the bad news - the fan clutch was not my problem.

Back to diagnostics.

1) I believe the thermostat is OK based on the fact that the top radiator hose is hot. Is that a valid assumption?

2) Is there any sure way to test the water-pump on while on the vehicle?
Bentley says to take the belt off and spin and check for play. I'm not sure that is a complete test. I'm looking for a way to tell if it is actually pumping coolant.

3) I'm going to test the aux. fan this evening. I'm really not sure if it is working or not. Question - With the air compressor on should the aux fan run regardless of whether the aux switch on the radiator is bad or not?

4) I'm looking for someone to do a coolant system pressure test (my luck it is a head gasket) but I'm having trouble finding a mechanic willing to diagnois problem unless I'm willing to let him do the work.)


Any other suggestions would be appreciated.

MB

[Mitch90535im]

Looks like "cooling system week" on the board. (bump)

[632 Regal]

if the switch is bad they wont come on.

[Mitch90535im]

Based on that I believe I should test the switch/fan low and high speeds by jumpering the plug. Sound reasonable?

[632 Regal]

Based on that I believe I should test the switch/fan low and high speeds by jumpering the plug. Sound reasonable?

[Derek A.]

The a/c turn on for the aux fan operates independantly of the thermo switch in the radiator. If the a/c compressor is running the fan should be on, if its not there is a problem. Generally an aux fan problem will not cause on overheat problem. Its only when you are in a super hot climate sitting still that it kicks in. Are you comsuming coolant ? when does it overheat ? Its possible tha the thermostat is open enough to allow some coolant flow but not enough to cool the engine when it get hot.

[Dan in NZ]

I replaced my fan clutch and still had overheating, same as you. It turned out my radiator was 75% blocked, so I took it out and had it cleaned out by a specialist, then re-installed. Good as new.

[Mitch90535im]

Its only when you are in a super hot climate sitting still that it kicks in. Are you comsuming coolant ? when does it overheat ? Its possible tha the thermostat is open enough to allow some coolant flow but not enough to cool the engine when it get hot.

Not consuming coolant. It overheats in slow traffic after it has warmed up and the needle has remained steady at 1/2 for 5-6 minutes. I guess the thermostat is a possibility, top hose is plenty hot. I didn't get a chance to test the aux fan yet, but I'm glad someome qualified the fact that the AC controlled fan switch is independent of the radiator switch. (got bad advise on that one earlier). Earlier was told that if the radiator switch was bad, the A/C switch would not work either. That should be quick enough to test this morning before work.

I suspect either:

1) Aux Fan (or related switches/resistors)
2) Water Pump (still haven't seen any advise on how to determine if it is actually pumping coolant)
3) Thermostat
4) Head gasket or crack

The odd thing is that this all started just after a coolant drain, flush, and fill. That's obviously why I suspected trapped air, but I've bled dozens of times, and there really doesn't appear to be any trapped air at this point.

[Mitch90535im]

Update - Aux fan runs on low speed with A/C on. Drove to work with compressor on this morning and temp still wanted to creep up above 1/2 mark. I'll test radiator switch this evening.

Beginning now to suspect either the water pump, or thermostat that is only partially opening.

Any recommendations from you guys at this point?

[Derek A.]

Can you feel hot air being pumped by the fan when the car is running ? How old is the radiator on the car ? After you shut the car off how long does the cooling system hold pressure ? If the top hose collapses quickly I would guess that you have a leak somewhere. How does the engine oil look ? Does the car make steam a lot out the exhuast ?