2005 Trailblazer fan running when first turned on - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum



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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 Vortec 4.2L I-6 Engine and Drivetrain > OEM Issues

OEM Issues Original Equipment Repairs and/or Problems

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  #1  
Old 10-07-2019, 03:05 PM
rnranimal rnranimal is offline
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2005 Trailblazer fan running when first turned on

I've been reading up and watching videos on how to do a coolant change and in some of the videos, they talk about idling and waiting for the radiator fan(s) to cycle on. But I've noticed that my fan comes on right after starting the engine and stays on as long as I idle. I have no idea if/when it turns off when driving (is there a way to tell?). The engine is stone cold when this happens and the A/C is not on. The fan doesn't come on if I just turn the key forward without starting the engine. It comes on after starting the engine. The temp gauge is at the lowest point.

No codes. No overheating. Seems to drive fine. Temp gauge rises until it reaches just a hair passed half and stays there (which I read is normal and these gauges are not really showing actual temp all the time but should show overheating). Coolant looks fine in reservoir and radiator cap. But I'll see what comes out when I drain it.

Last year the water pump was replaced at the dealer after I noticed a noise and could see the fan moving off-balance.

Is the behavior I describe the normal operation of the fan? Or should the fan only be coming on when reaching certain temp?
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  #2  
Old 10-07-2019, 04:28 PM
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EnvoyBoy2004 EnvoyBoy2004 is offline
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This fan is controlled by a viscous clutch, which means that is will always spin because the viscous material always causes some friction. It is normal for the fan to rotate when the engine is running, as the temperature of the coolant increases beyond around 220 - 230 degrees, the PCM will signal the fan clutch to increase the fan's speed.
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Old 10-07-2019, 05:01 PM
rnranimal rnranimal is offline
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Quote:
Originally Posted by EnvoyBoy2004 View Post
This fan is controlled by a viscous clutch, which means that is will always spin because the viscous material always causes some friction. It is normal for the fan to rotate when the engine is running, as the temperature of the coolant increases beyond around 220 - 230 degrees, the PCM will signal the fan clutch to increase the fan's speed.
Thanks! So during the point of the flush where the online instructions say to wait for the fan to come on, I'll be listening for the fan to spin faster?
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Old 10-08-2019, 12:20 AM
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EnvoyBoy2004 EnvoyBoy2004 is offline
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Yes, but I don't know what that is supposed to do with doing a flush. All that needs to happen is for the thermostat to open and allow coolant to circulate.
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Old 10-08-2019, 12:23 AM
rnranimal rnranimal is offline
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I'll have to go back and watch the videos but I think it had something to do with the burping after filling.
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