Reduced by the Fan

[FlyRod]

OK, I am getting real ****ed now! I've just read a nice article in motor trend magazine about the three major brands of diesel trucks. The GM came in 2nd place! From what I gathered from the article, the reason GM came in 2nd place was basically because the fan clutch kicked in during the pull test. As we all know, if the fan clutches in, you lose all kinds of power. OK folks so what's up with this fan? Why is it kicking in So soon? I'm no expert but it does seem to be a little over anxious. The Ford (1st place) did not have that problem and it did not overheat or blow up. Any of you GM experts want to shed some light on the subject? Does GM realized there is a problem here and if so are they doing anything about it? I'm glad my truck is well protected in the cooling department; however, I think they may have gone a little overboard.

[More Power]

The fan-clutch in these trucks engage when the air temperature between the radiator and the fan-clutch reaches approximately 195 degrees.

There are four heat exchangers in the airflow path between the front of the grille and the fan-clutch (in Allison equipped trucks) - ATF cooler, A/C Condenser, Intercooler, and Radiator.

My guess is the heat load caused by the intercooler (and possibly the A/C condenser) is what caused the fan-clutch to engage in the MT test.

From the plethora of notes taken at our most recent Pull-Off event, it appears just one Duramax equipped truck experienced fan-clutch engagement during the hill-climb. And, that one was largely due to the A/C being used just before launching on the hill. We recommended drivers not use A/C on the 3 mile trip from the campground to the bottom of the hill, to avoid engaging the fan-clutch during the pull. To be fair, all drivers or all three brands of trucks were given the same advice.

MP

[rdanley]

i am having the same thing with my fan clutch it really robs the power. it kicks on way to much though. i live in oklahoma and going down i-35 from kansas border to my home town in lawton (texas border)with a load of around 7000 pounds, everytime i hit a little hill it kicks in and you can fill the power loss. is there anything that can be done about this. seems like all of the safety features that are on the ally and the lly are killing this setup.

[MaxedOut]

Just curious if the people with the clutch fan problems have any restrictions causing the fan to engage more often. Grill inserts can reduce air flow by a great deal and cause this problem. I noticed on the hot days with the AC on my clutch fan was coming on a lot. I took the grill inserts out & it's rare that it comes on now. I was a little worried that the radiator would get blasted with bug with the inserts out :eek: so I modified the winter front. I basically cut out the material leaving just a frame and replaced it with screen. This allows more air flow than with the inserts in & also protects the rad - best of both worlds.

[Kennedy]

I don't know the specific data for fan load, but I'd hazard a guess that the fan clutch pulls <10% of rated torque when fully engaged.

I also understand the Dmax clutch calibration to be 195

[Modified]

I have a modified Cold Front with the screen sewn in, that I bought from Maverick. It works great for keeping the bugs off the coolers.
I have however, noticed when pulling my 5ver in 80 or 90 Deg weather, that my fan is engaging, when it rearly ever did before.

I do not use the bug screen anymore when pulling in summer, because it definitely reduces air flow.

[chipper]

I do not use the bug screen anymore when pulling in summer, because it definitely reduces air flow.
__________________________________________________
Modified,
So does a radiator core 1/3 plugged with bugs & are they a bitch to get out 3rd core back in the stack!! :D

[LanduytG]

The fan engages because it needs to. Mine was one that engaged at the pull off and when it did I lost 2 mph,big deal 2mph. But in hung in pulled well to the top and things stayed cool. This is a truck made to work and pull and when you pull you are going to make heat that needs to be gotten rid of. If the fan bothers anyone then don't tow with it or by a car.


Greg

[Showgood1]

There is a electric fan clutch available for the goat rigs and they were supposed to go to some type of electric fan clutch on the '04 gasers. I haven't looked at one yet to see. So how 'bout it Kennedy? How about a electric fan clutch for the D'Max? I just hope that who ever else comes with one doesn't charge the 800+ for one. Oh and its made by C@mmins not goat inc.