I Have A 2003 2500 Duramax And When I Tow My 32 Ft 5th Wheel In The Summer . The Fan Roars Every Time I Stop At A Stoplight Or Starts Roaring As I Drive Down The Road. It Even Roars In The Winter After Setting In Garage First Thing In The Morning. Does Anybody Else Have This Problem? I Had The Fan Replaced By The Dealer Last Year But Is No Better .

I Have A 2003 2500 Duramax And When I Tow My 32 Ft 5th Wheel In The Summer . The Fan Roars Every Time I Stop At A Stoplight Or Starts Roaring As I Drive Down The Road. It Even Roars In The Winter After Setting In Garage First Thing In The Morning. Does Anybody Else Have This Problem? I Had The Fan Replaced By The Dealer Last Year But Is No Better .

This is normal.

What you describe is definitely normal.

DEWFPO

Mine does the same thing.

Yea when my 8.1 did it for the frist it even made the "old lady wake up" and say what the h--- is that and I told her that I was overworking my truck and needed to upgrade to a d-max. Well she didn't buy that and went back to sleep.

thanks for the replies from all of you. i guess that answers the question

I told her that I was overworking my truck and needed to upgrade to a d-max. Well she didn't buy that and went back to sleep.


That's a good one!!! I'll give you an A for effort!!!

Mine does the same thing, to me it is a reassuring sound when towing the trailer.

Does anyone know if the fan is tied in to the engine oil temp in some way. I have noticed when towing heavy loads with my truck (12,000 lbs or more) the fan will engage and roar for quite a while. When it does engine temp is fine (190-200) and the trans temp is also fine (200 or so). The only thing that I have noticed is that when it starts my oil pressure will be around 45 psi and when it stops the oil pressure is back up around 60 psi. Just wondering.

The fan clutch engagement is not tied to the engine oil temp (at least not directly). It is however tied directly to how much heat your engine is trying to dump (throught the radiator). As the air flow thru the radiator gets hotter, the thermostatic clutch reacts and adjusts the silicone to grip the fan blade(s) more to increase airflow thru the radiator.

With the engine putting out allot of heat when towing the engine oil can thin out a bit potentially giving you slightly lower oil pressure. As the engine cools, the oil cools and thickens back up. You may want to try a synthetic motor oil and see if you notice the same pressure changes when towing.

DEWFPO

My fan is really loud in the morning sometimes too. Why would it do this if the motor is cold? When it has done it , it was probably 35-40 degrees.

This occurs because when you last shut off the engine, everything under hood was heat soaked. The thermostat in the fan clutch reacted and engages the fan. When the engine is started again it takes a minute or two for the thermostat to react to the cool conditions and dissengage the fan.

I agree it is weird when it's +5F out and as you pull away from a cold start your fan is roaring for the first 75 feet or so.

DEWFPO