Engine Fan Question

[DURA-MAX3]

Has anyone with an lly engine noticed the engine fan coming on with the brakes in the tow/haul mode. This is wizzing me off. I don't want the fan coming on all the time like that and was wondering if it can be turned off or set different at the dealer.The fan seems to come on more often than my 01 dura/ally...Thanks for your replies...

[Kennedy]

If it is coming on, things are hot under the hood, and it needs to be on. It senses temp of air coming through the coolers and radiator.

It needs to run to keep the AC and intercooler operating efficiently, and is basically picking up the slack when the ram air goes away.

My 6.5 is in TX now and Karl was saying the same thing was happening with my special fan clutch installed. He also said that the AC worked GREAT!

[DURA-MAX3]

So its just a coincidence that it comes on with the tow/haul mode on. Just seems like it comes on a lot more than the old style engine.My 01 hardly ever came on...Thanks...

[Colorado Kid]

I can think of at least three reasons why the air going by the fan on an LLY might be warmer than on an LB7 under otherwise identical circumstances.
1) The Variable Geometry turbo is used to create back pressure to make EGR possible. (Exhaust pressure must be higher than pressure at the point where the recirculated exhaust joins the intake air stream). Higher exhaust pressure = more heat retained in cumbustion chamber during exhaust stroke.

2) EGR gasses are cooled in a gas to liquid cooler . . .tranfering heat to the cooling system.

3) Even after leaving the EGR gas cooler, the gas temperature must still be higher than the coolant temperature . . . this hot (warm?) gas stream is added to the intake and passes through the intercooler, which cools the intake charge by transfering heat to the air headed into the radiator.

Anything that increases the water temperature in the radiator or the air temperature in the intercooler will increase the temperature of the air at the fan.

[Kennedy]

It sure SEEMS that the compressor out temps on the Garrett turbo are HOT compared to the IHI. This is a casual observation only, and may be influenced by the metal tube alongside the engine connector vs the silicon hose on the LB7...

[lafrance]

Just a side note,
I to have spoke to my dealership regarding the noisy fan. I was told this morning that G.M. powertrain is working on a fix for this as they are aware of the annoyance factor. My 04 duramax
at idle constantly has the fan clutch kicking in and out.... Also a little of topic but the dealer I spoke with also recommended additional fuel filtration and mentioned the 05,s will probably be coming from the factory with a new racor system mounted on the frame rail. They are currently fitting these units at additional cost to every new D-max that they sell.Cost of Racor kit from them 550.00 plus 2hrs install time.Racor has specifically targeted this kit at the Duramax market and refers also to G.M. dealers as having access to these kits. The current racor on our trucks (04,s) is a 10 micron
The racor kit is equipped with a 10 micron filter. Looking at the fuel analysis results it would seem that a 2 micron filter is more suited.
Having just paid 50,000 for this vehicle I find it difficult to understand why G.M. does not fit this kit at their cost as they have obviously found that it is needed.anybody with other info,
This info is from a reliable source. The racor part nos is RK32347.
Thanks.

[Darip]

Dura-Max3, I am having the same problem that you are on my LLY. I only have 1100 miles on it but the fan runs alot more than it did on my LB7. Pulling a 5,000 pound trailer down the freeway at 75 mph in 68 degree weather, the fan runs almost continuously and really hurts the power. I am new to the Diesel Page and appreciate all of your input.

[Darip]

I took out the Billet Grill insert that I installed on my grill and the pickup seems to work fine now. You might try this if you have a grill insert or a different grill in your pickup.

[Chevy2DMAX]

lafrance, what kind of truck did you get for $50K? I just got a new 4x4 LT LLY crewcab dooley for less than $39K.

[letsgo]

Is this along the same lines???

On a number of occasions after a 5 to 10 mile haul climbing to 6000' and 8000' towing in towhaul mode, an extremely loud noise would come from the engine area just before going over the crest of the hill/mountain, speed was 55mph @ 2800rpm to 3200rpm the electronics were in compleate control, not sure whether it was the engine fan,the noise would instantly disappear as the truck and trailer would reach the top and upshift to a higher gear, neither the rpm or speed changed, when this noise occured, the engine temperature was always constant going up or down hills the tranny temperature would fluctuate a 1/16th, I looked at the tranny oil, it looked OK and smelt fine, at one point I had ONSTAR do a diagnostic while the noise was taking place, no fault codes detected.

any input would be welcomed,

[mark45678]

I must agree the lly fan comes on when its idleing even be for its warm... I am not talking about cold start fan theres no way around that. it cycles on and off about every 10~15 seconds with water temps at 185*? (as seen on the juice monitor). the fan gives slight sound of speeding up and kicks out before it gets up to crank speed.

[RocketsDmax]

FYI, GM has overdriven the cooling fan on the new lly by about 1500 rpm at idle, Probably for the poor A/c performance at idle. My 03's fan works its ass off during warm day trips around town and going to the river. Havent had any customer complains about this being a problem here yet.