Aux Fan Sensors

[jmc1590]

Hey all,
Recently I had a chance to inspect and test a majority of the cooling system trying to resolve a overheating condition. In particular, the high and low speed aux fan sensors. (Of which both failed!)
The low speed sensor appears to be a 80 degree unit, and the high speed sensor appears to be a 99 degree unit. (Both in celsius.) What I'm wondering about is what the stock low speed sensor should be, 80 or 91? RealOEM shows the 91 as a stock item, but I like the idea of the aux fan kicking in earlier with the 80.
The other question is which vehicle is the 80 degree sensor stock on, or does anyone happen to have a part # handy.

Thanks!

[jlevie]

Does the overheating problem only occur at low speeds or in stop and go driving with the AC on? The aux fan is only to provide addition air flow in those conditions. If overheating occurs with the AC off, you have to look elsewhere for the cause (fan clutch, thermostat, air in the cooling system, bad head gasket).

[jmc1590]

The overheating problem was resolved. It was air in the system. Trying to bleed from the thermostat housing didn't resolve the problem, however with the front raised, removing the low speed temp sender allowed a majority of the air to be removed.

Which brings up a question... After bleeding the system, I ran the vehicle with the expansion tank open while "massaging" remaining air out of the system. I noticed that my coolant level will drop while the engine revs. Is this normal? (Reducing the engine revs will allow coolant to return to the tank.)

I also found that several of my radiator hoses were soft to the touch after the bleed. (i.e. - no presure.) By reving the system with the cap off, I watched the coolant level lower, at which point I fastened the cap. This seemed to presurize the system. When cool, I topped off the coolant level. As of this morning, no more overheating. (However... Now it wont idle!)