99 Tahoe Fan Issue

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  #1  
Old 07-29-05, 07:50 PM
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99 Tahoe Fan Issue

I may be loosing my mind, but I think the main cooling (direct drive) fan on my Tahoe is working much more then it should. Perhaps I'm hearing things, or think the fan should work differently, but lately it seems the clutch never dissengages, or slows down. I know that when the engine is cold, and for the first few minutes the fan runs at full speed, it sounds like a blower when you accelerate and the car feels like it's pulling a trailer. However, after a few minutes the fan slows down, and you can barely hear it.

Lately however the fan sounds like it's going at full speed all the time. Even when the outside temperatures were 100F the fan was still fully on. Could the clutch fail so that it's always fully engaged? All of the failures I've seen in the past were opposite, where the fan would not spin fast enough and the engine would overheat. Is there a way to test this, or is there a rule on how long the fan should work at full speed? I've never had the "opportunity" to work on a clutch fan before, all of my other cars had electric fans.

Thanks,

G
 
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  #2  
Old 07-30-05, 06:28 AM
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Yes it's possible for a fan clutch to lock up, and run directly with the speed of the engine. Sounds like a a crop duster "prop job" plane is inside the engine compartment.. The only way I know (I'm sure there is a proper technical way,) is to try and spin the fan by hand. (Yes, please make sure the engine is turn off..) You should be able to spin it fairly easily, but with some "drag" or resistance. If you have to force it, or it won't move at all, then the clutch is bad..
 
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Old 08-01-05, 09:57 AM
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I tried to spin the fan by hand. One way it barely moves at all. The other way it can be pushed, but it requires a fairly strong force. I went ahead and ordered the clutch anyway, it was only $40. I don't have another car to compare the resistance, but I know the car sounds and feels differently.

The other thing I heard while the engine was running was fairly loud "vacuum" noise on the passeanger side of the engine. It sounds like a large vacuum leak, but the engine runs perfectly, and as far as I know nothing is out of the ordinary. Is that noise supposed to be there?
 
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Old 08-01-05, 07:27 PM
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Air rushing through the intake tube, and into the engine can often sound like a vaccum leak..I'm not sure if this is what you're hearing or not..I'd assume being that it runs ok, that's probably what the noise it.. But diagnosing a noise when ya can't hear it, is always kinda tough...
 
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