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Old 07-29-2016, 10:11 PM
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hydraulic cooling fan problems

08 wk 5.7. Any ideas why my fan does whatever it wants? It'll Rev up so high at times it sounds like an airplane taking off. Is there a control module or something that I can check? It's very random and of course it responds to engine rpm as well...then gets faster when coming to a stop. So fast that the bearings will chirp at times. Can be sitting at a light in 105 with no wind and not be on but times like this morning it was 68 and raining and it was going nuts??

Little history behind it...all started one day literally 2 minutes apart I got a Crack in my radiator and ran low on coolant for about 5 miles (didn't go but 1/8" about normal as I was almost home). Same time I noticed steam/smoke come out of my vents and a/c stopped blowing cold. Replaced radiator everything went well. Went to charge a/c...no freon...can't find leak. Charged it up and no pressure on low side so there's a blockage somewhere but no one knows what or where and I hate to just start guessing at it.
So no a/c now and my fan seems like it's about to spin through my hood.
Any ideas? Are the 2 issues even related?
Has anyone ever ditched the hydraulic setup and put dual electric fans on a thermostat? Only 38k miles on the clock.

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Old 07-29-2016, 10:25 PM
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Re: hydraulic cooling fan problems

The hydraulic cooling fan is controlled by the PCM. It uses inputs from the engine coolant temperature, but also the pressure in the AC system, to control the fan. So a problem in the AC system can cause the fan to go to high speed.
So i would first solve the AC problem, and then see if the hydraulic fan is ok.
The steam/smoke which came out of the vents, could have come from the evaporator. This one sits inside the HVAC housing and a leak overthere will bring the freon inside the cabin. Do you remember smelling it at the moment the smoke came out of the vents?
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Old 07-29-2016, 10:29 PM
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Didn't smell anything...it was a very small amount. Makes sense tho that the pressure will aid in the control of the rpms...I guess. Stupid system for sure. I got an expansion block for it gonna try that this weekend. But with there being a blockage something would have to have broken correct? Just gotta find it
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Old 07-29-2016, 10:43 PM
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Also afterwards it held a vacuum for upwards of 40 min...charged it up and nothing on the low side. Was almost 2 weeks before I was able to take it to an a/c shop for diagnosis and it was still full..they put a vacuum on it as well and founds no leaks. So weird!!
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