02 envoy, 6 cyl, loud wooshing noise when engine is cold. fan clutch seems fully engaged. goes away when engine warms up. is this normal or does fan clutch need replaced

Should idle between 500-600. Clean your throttle body with the battery disconnected to help with the fluctuation. The roaring very well could be your fan clutch. Fan clutches are a known problem with our platform. If engaged, will sound like an airplane.

Fan clutches are stiff and loud till vehicle runs a bit, as fan clutch mechanism warms up drag on clutch mechanism releases pressure and will free wheel.
Do not mistaken this with, when engine hot, clutch engages to help cooling system which is normal.

2008 GMC Envoy is only equipped with one of two engines:
4.2L (254") 6-Cylinder SFI
5.3L (325") V-8 SFI

Niether of these engines are equipped with an EGR valve, so I guess the probability of that being the cause of your noise is pretty much zero to none.

If you believe the noise is being caused by the exhaust ststem, then the only way to verify that is to inspect the exhaust system. Leaks are easier to verify with the engine running.

With that said, there is also a Technical Service Bulletin (TSB) that is published by GM that addresses customer complaints about loud noise that is being caused by the electro-viscous engine cooling fan clutch. Some people describe it as exhaust noise and others describe it as the engine "racing" or "roaring".(even though the tachometer (if equipped) will be reading normal)

It basicly says that it can make noise on startup due to high rpm of the fan which goes away once the electric solenoids open and allow the fan to start free-wheeling. GM says this is normal operation. You might want to check to be sure this is not what you are hearing. (it can be pretty loud)

Fan clutch failure is common on these........and very costly to replace. With the engine cold, engine off, reach in and turn the fan, it should turn with minimal resistance, if it has heavy drag, or wont turn at all, it needs replaced.

That's the fan clutch for the radiator fan. It has a thick fluid in it and in this cold weather it is ispecially thick. This makes the fan turn almost at engines speed and that makes the roaring noise. After it has been spinning a while, the fluid gets warm and gets thinner. that makes the fan turn slower than the engine. This is normal and needs no attention.

We have the same tapping sound on our 2003 Envoy six cylinder engine. I believe the sound is coming from the radiator fan clutch assembly. When the engine reaches its operating temperature and the fan clutch engages, the tapping sound goes away.

most fans are clutch fans and they work or are engaged by temp.most all will spin under really cold conditions.this is normal.but to be sure, with the motor off and key in your pocket grab the fan and see if it wiggles or has any slop. if not alls good

it may need a lifter or valve adjustment when cold they will tick or knock depending on how loose or worn out then when it warms up they swell with heast and noise stops. after adjusting or replacing it will stop making noise

The emission controls (or PCM) do what you are describing intentionally. There is an electrically controlled fan clutch. It is noisey when cold. The shifts are held to increase engine speed to heat up the catalytic converter faster.

I would guess it is the electronic fan clutch. It will cause the fan to run too fast (very loud) and the light will come on sometimes.