Yes it is horrible, try to tow something in Fl and that fan comes on and slows down everything, people look at you like you have an airboat engine under the hood. Doesnt sound like a quality GM product, sounds like something is broken or poorly modified. Is there an electric fan fix or do I have to wait and see the 2005's. I think GM should come out with a new version every quarter, Just think LB7 LLY 2005 and something else in one year!! WE are not too far offhttp://dieselplace.com/forum/smileys/Clap.gif.

That thing is moving some serious air. I like the sound http://www.dieselplace.com/forum/smileys/Big Smile.gif


Do you have some kind of bug screen that might be restricting air? Mine doesn't run all that often and when it does it only runs for about a minute untill it cools down. Of course it hasn't been very hot this year either.

Well, it's been hot here in Arizona and my fan runs more than not. I want to run an AUXILLARY fan to see if would help. I'm really tempted!

That thing is moving some serious air. I like the sound http://dieselplace.com/forum/smileys/Big%20Smile.gif


LOL- Hey- I really dont mind it either- something must be wrong with us. If it gets too loud I just turn up the xm- LOL

The fan sure does it job here in AZ, everytime mine kicks on the temp drops!!!!http://www.dieselplace.com/forum/smileys/Big Smile.gif

No bug screens on my truck. I just keep it washed. The sound is a personal preference, but it is a loud howl.

That's it's job.... Can't understand the noise complaints, Yeah it makes noise, it's a real truck fan, on a real truck. http://www.dieselplace.com/forum/smileys/Approve.gifWant peace and quiet? I'm sure some little import econobox will be much quieter.....

Silveradogs is correct - that is the fans job. How many of you had 6.2 and 6.5's where the fan came on late, never could cool the engine under load, and the vehicles ran hot while towing. You could never use your full power, had to back out of it, and saw temps that got into the red zone quick. The DMAX cooling setup is fabulous - I can never get the damn thing excessively warm no matter what I tow - try 33,010 lbs over the grapevine in 100 degree weather with the AC running. Fan ran, but engine temp never got over 210. And yes, the fans run for a few minutes on startup in the AM - so what? Great cooling system. And for those of you who wish to go to electric fans, I gotta laugh. I have never been able to buy a electric fan big enough that moved enough CFM of air that would fit in a pickup or car. I have electric fans (highest CFM I can find) with aluminum radiators in my hot rods and collectors, but they don't move enough air to cool under conditions found with a DMAX. Yes, maybe the fan is a little noisy sometimes in a DMAX, but it is one of the best and highly prised features of the truck for those of us who have had diesels for a long time (look at my signature). GM finally got cooling right - now if GM would only get injectors, sheetmetal thickness, paint, tailgate cables, and on and on RIGHT, they would have a great truck!

Gardener, What temps should I be seeing and when should I get worried? It gets damn hot in S. Fl with the humidity.I get my truck up to 212 while towing on occasion but it backs down a few degrees once I lay off of the pedal and let er breath. Trust me a 92 degree day with 80% relative humidity is a lot worse than an Arizonian 109 degree 4% humidity day.( whats up with the Ducks uniforms in Oregon, fluorescent green?)http://www.dieselplace.com/forum/smileys/HiHi.gif cant wait for football

gardnerteam,


When you say GM got cooling right, that is past tense. The LLY (at least mine) will get hot towing GCVW over 18,000#. Not enough cooling. I shut my AC off when it gets to 230 F.

Just wait until gardnerteam gets his 05 LLY he will be changing his mind http://www.dieselplace.com/forum/smileys/Big Smile.gif


My 02 LB7 fan and cooling system worked flawlessly, my LLY is on all the time. It does get very anoying and the truck looses power. Mine will come on unloaded running 80-85mph on a hilly interstate. You cannot tell me the fan fully engaged is moving more air than a truck running down the highway at 85. If anything I would guess it is hampering cooling flow.......................


IMHO this is problem and needs to be addressed by GM

IT IS moving more air with the fan even running down the highway at 85. The attitude displays a digital read out of the engine temperature. If you get it up to 210 degrees and the fan doesn't kick in it will very slowly come back down. If the fan kicks in it falls down VERY quickly. It is quite amazing to see just how much difference that fan makes.

I guess you guys never heard the fan kick in on a freightliner detriot diesel. You think yours is loud. This fan is like 30 or more inches in dia.

OK - I agree my experience is all on pre LLY, except I know of several LLY's that are used just for towing on the west coast between LA & Seattle, which is nothing but grades over the Grapevine, Siskiyous (spelling is wrong), and several grades in Southern Oregon. They all report no problems. My 05 is due in 3 weeks and I guess I will find out. But I still say no electric fan will do the job. OK - start throwing ---------------

On the way to the dealer on Saturday I am going to weigh my truck and trailer. I will take that slip to the dealer. We will then test drive. I hope they find some minor problem. I don't mind the fan coming on, but I will not accept 220 225 temps that force me to back off and turn off AC. This happens at 75 F or 100 F outside temps. Alot of people talk about how heavy they tow, but there is a definate break over point from the posts I have seen. My main testamony is my buddy pulling next to me with a similar trailer but with an 01 D/A. His temp gauge never moved. Mine went to 225 and I shut off the AC. I did not back off, are you kidding? Let him beat me? The temp stabilized at 220 and we finished the hill. This was headed up from Durango to Purgatory at 75 F outside. Maybe I am too extreme, racing 5th wheels up hill.

My LLY runs up when temp crosses about 87-90 degrees with low humidity- unloaded city driving, and the sotp test says it's robbing a bunch of power - I'm not worried about the noise. My temp gauge never rises abouve 205ish, but when the fan comes on it doesn't drop at all either.

I weighed 21600 combined in 90-95 degree weather (low humidity) and towed 900+ miles from So Cal to Oregon. There are several good pulls on the trip (Cajon Pass, Shasta etc). My temp gauge NEVER rose above 210. My tranny was always less than 210. I had climate contol set at 68. I let it pull up hills with the cruise set at 62. Sure, the fan came on, but only on hills and when accelerating. I dont mind hearing the fan.


This thing pulls great.

My clutch fan comes on when I first crank the truck up after having run it 30min to an hour before but the temp gauge says it is 160 I thought that it was only supposed to engage when the temp got above 210ish? Should I have this checked out?

That sounds way to cool to kick on. If it was me, I would check into it. Out here in AZ the temps are pretty high- My fan does not come on till over 200 I think.

my boss's 3500 LLY DRW fan comes on like most of yall are saying and like most we are towing usually between 12-20k boats around louisiana with 95-100 degree temps, and almost 100% humidity, and he has a polished grill cover on it and i know that makes the fan kick on more than normal, but the temp has never rose above 210 and we usually have the a/c set at 60 and its blowing full blast


we have a guy right now pulling a 15k lbs 40' Skater to NY from here and we just talked to him and he said that his fan isnt kicking on anymore than it does pulling his 7.5K lbs 26' Eliminator

My clutch fan comes on when I first crank the truck up after having run it 30min to an hour before but the temp gauge says it is 160 I thought that it was only supposed to engage when the temp got above 210ish? Should I have this checked out?


That is normal. The fluid settles in the clutch when sitting, causing the fan to run upon initial start until the fluid is fully circulating within the fan clutch. Once that happens, the fan clutch will stop/disengauge until you reach the higher temps.

Alright thanks sammy, Yeh it only stays on for like a min or two at most. But I just installed my edge/tude and I really didnt feel like taking it off so I could have it checked out by the dealer.

This is getting to be a very common complaint. Wonder if there is a fan that is quieter at the higher RPM, yet as effective at low rpm.

I've never paid much attention to this unless I'm towing something. Is this the noise that soundsl like an airplane propeller under the hood that cycles on and off????

yup

Glad to hear you boys are towing heavy with those LLY's and not overheating. Seems many LLY owners are having problems towing! http://www.dieselplace.com/forum/smileys/Ermm.gif


Oh yeah, the fan! http://www.dieselplace.com/forum/smileys/HiHi.gif Ditto Max Power's comment. I tow heavy 25500 GCW with 40' 5ver on my tail. On long climbs I'll see 230* engine temps, fan kicks in and cools fairly quickly. Yeah its noisy, but at least I know its working. JJ http://www.dieselplace.com/forum/smileys/Big Smile.gif

JJ, 230 is too high IMO. I saw where JK has lower temp clutches.


No complaints about effectiveness. My complaint is that it get that hot and needs an airboat fan to make it "right", in the first place. Properly designed, should not require 6000 cfm. The small grill, overly-stacked radiator components, etc require the "brute force" solution. Anything that makes me (or my passenger) jump is not "right"


Where would you be if it failed?

Where would you be if it failed? Dang masterp2, hope you didn't put the "maloicks" on my fan! http://www.dieselplace.com/forum/smileys/Pinch.gif


I've seen posts where guys that owned the LB7's are concerned about 230* engine temps with their LLY's. Seems reasonable to me that increasing HP/TQ in any engine is going to create more heat.


My experience is only with the LLY. I'm really, really, really, really slow when it comes to "meck-a-nickel" stuff so I have to read the owners manual so I don't blow things up! http://www.dieselplace.com/forum/smileys/Confused.gif I took GM at their word that engine temps up in that high range are ok and not an overheating situation. The noise doesn't bother me, especially given its cooling down the beast! I am thoroughly enjoying driving this "fat ass" truck! http://www.dieselplace.com/forum/smileys/HiHi.gif


I do agree there is an awful lot of "sh_t" up there around the radiator generating heat. 6000CFM, I had no idea! Ignorance is bliss! JJ http://www.dieselplace.com/forum/smileys/Big Smile.gif

I took GM at their word that engine temps up in that high range are ok and not an overheating situation.


Sure, it will definately get you to 36,001 mi. Sorry for my synisism (and spelling).


But lose the clutch and you are now a steam locomotive (unless you are on a downhill final approach to home).http://www.dieselplace.com/forum/smileys/Approve.gif Ought to be able to get home without it IMO. I am relocating my new fanned tranny cooler to help this out. i may never here the fan again, hopefully. Not to mention real AChttp://www.dieselplace.com/forum/smileys/Cool.gif.

OK, you peaked my curiosity!http://www.dieselplace.com/forum/smileys/Ermm.gif What kind of finned tranny cooler are you installing? And what does that have to do with the AC? Told you I'm mecha-nickel-y challenged! http://www.dieselplace.com/forum/smileys/HiHi.gif JJ

Moving the cooler, resizing it, add fans, presto chango, more airflow across the condenser and radiator, lower intake temps from a more efficient intercooler, lower temps across the cooling stack=less fan clutch engagement, so the theory continues. Oh yeah, and the tranny never sees over 180 again.


BTW, GM knows that the 50/50 coolant mixture boils at 236 deg, pressurize it to 14 psi and it boils at 260. So that is where they can figure you have 30 degrees more to blow the top. Trouble is, heat still kills engines, and everything else. 36K warranty has me seething with the stupid numbers they say are OK. I can't stand the way they trim the warranty to suit the engineering incompetence.

Well this is my first post and i'm not to sure of alot of the terms that are being used. I'm in San Diego where its been in the high 90's for a few weeks. My 04 LLY hasent engaged at high speeds, its always from a start or a rolling start. I went for a test drive today 9/10/04 with the Tech and it engaged! From his explaination its working correctly. My concern is when GM converted from the LB7 to the LLY and knew this was increasing HP and TQ but didnt increase the cooling capacity for a truck thats specificly designed for towing and is one of the most expencive vehicles they sell, the hell with the sound of the fan. Wheres all the concerns about the POWER LOSS. I purchased the truck for the towing power. The service Mgr. told me that he was talking to a service Mgr. in the desert area ie. Arizona/Nevada and they are getting a lot of complaints out there. They gave back my truck that they had lifted with a Fab-Tech 8" kit and put 30" tires on the day it rolled into town and said to continue driving while they look into the info I pasted to them about the paper pan gasket that Allison said should be changed out at 7500mi. to help increase fluid flow. I told them about the forum and they said in order to get the MFG to move it is going to require alot of dealer complaints before they will want to for go a BIG PUBLIC RELATIONS problem. I think with another or better cooling device the whole problem will disappear. And I hear they are monitoring forums just like this. Keep up the info transfer and I will give an update when they call me on Monday.

Welcome to the site BIGGERRED. DP is a great forum for airing issues, gathering intel, and mutual BS from time to time. Your fan operation sounds normal for the LLY; some love that sound, others hate it! http://www.dieselplace.com/forum/smileys/HiHi.gif I don't believe you will be too disappointed in the pulling power of the LLY, I'm pulling a 40' 18k GVW toyhauler with no problems. Others are towing much heavier.


Some are having overheating issues, likely the guys mentioned in Arizona. Watch those engine temps. http://www.dieselplace.com/forum/smileys/Approve.gif


masterp2, Thanks for the explanation. I've seen other posts where this is being worked on, I just didn't understand the application. I'll follow these posts to see the results.


JJ http://www.dieselplace.com/forum/smileys/Big Smile.gif

about the paper pan gasket that Allison said should be changed out at 7500mi. to help increase fluid flow.


Please explain??http://www.dieselplace.com/forum/smileys/Confused.gif How does a pan gasket affect fluid flow?


Welcome to the DP.


Biggerred, your fan should turn off after a short rollout after initial startup, then stay off for the remainder until you heat up. If it is coming on everytime to drop rpms to idle, while your truck hasn't warmed up yet, it is malfunctioning. Don't misunderstand, the fan spins under a viscous force 100% of the time. If your hear it when you step on the go peddle (distinctive roar) then the clutch is engaged, and applying more turning torque to the fan making it spin faster in proportion to the motor. This is only to occur when the air temp across the fan is high, this can happen whenever you stop if the engine is hot, heat builds up there while waiting for green, then the clutch engages, and then soon disengages when that builup of heat is purged.Edited by: masterp2

Announced for 05:


The new cooling system advantages:

• A reduction in parasitic losses due to disengaged fan speed with a corresponding increase in
combined city/highway fuel economy.
• A significant improvement in idle A/C performance (driver/passenger comfort) as well as an
ability to idle with A/C on for extended periods in very high ambient temperatures.
• A reduction in customer complaints normally attributed to unusual engine noise or
transmission noise/delayed shift, which are actually fan noise issues.



Looks like the electro-viscous fan will solve all our problems. Now if we can only compel GM to put it in a TSB. Everyone go to the dealer and tell'em your dog died when the fan kicked in at 70 mph.

Announced for 05:


The new cooling system advantages:

• A reduction in parasitic losses due to disengaged fan speed with a corresponding increase in
combined city/highway fuel economy.
• A significant improvement in idle A/C performance (driver/passenger comfort) as well as an
ability to idle with A/C on for extended periods in very high ambient temperatures.
• A reduction in customer complaints normally attributed to unusual engine noise or
transmission noise/delayed shift, which are actually fan noise issues.



Looks like the electro-viscous fan will solve all our problems. Now if we can only compel GM to put it in a TSB. Everyone go to the dealer and tell'em your dog died when the fan kicked in at 70 mph.





I haven't heard of an elctro/viscous fan clutch, how does it work differently than just thermal/viscous

To add to that, I looked at an 05 and all appears to be the same as far as fan/clutch/radiator????

http://www.gmtechlink.com/arcv_pdf/7_02_e.pdf


For earlier light duties, EV explained.

http://www.gmtechlink.com/arcv_pdf/7_02_e.pdf


For earlier light duties, EV explained.


Thank you for the link. This sight is great , you never stop learning.


bummer is, it doesn't sound very easy to retrofit.

My fan also comes on for about a minute when the engine is cold. From what I have read so far, I understand that this is due to the fluid settling in the clutch. It always returns to normal after driving a block or two. Funny thing is, I also have a 2004 2500HD 6.0 gasser that never does this. I always assumed that both trucks had the same size and type of fan clutch - could I be wrong about this? I don't worry about it because I've never seen the temp on my LLY D/A go above 210 towing my 14200# fifth wheel through the flat lands of the TX and LA Gulf Coast. Anyway, just as a point of interest, humidity does not have any influence on your cooling system - dry air at 100 degrees is just as hot as humid air at 100 degrees to a closed cooling system.

Humidity does affect cooling ability. Humid air can remove more heat because it has more mass. CFM is the same, but the mass flow rate is higher, therefore able to pass more energy along.

This is going to be interesting!


Matt, how would you say humidity affects your AC vent temps?


Peanut, I am very interested in the 2 fan clutches, especially the gasser, and would like to know if it is the same part number. Also are the fans identical?

AC vent temps depend on a whole lot more than outside air temp. The condensor will be more efficient at higher outside air humidity. But that does not mean you are going to feel cooler in the cab.

It was an easy question. Same OAT, same conditions, except humidity is 80% vs 20%. Which condition yield lower vent temps????

Masterp2, I usually start of by saying " I could be wrong, but..".


Unless I am missing something, automotive ac units use a fixed orfice expansion system. If the refrigerant coming back from the condensor is at a lower pressure, then after the expansion it will be at a lower pressure resulting in a lower temp for the evaporator.


So, yes the whole system will pull more heat out of the cab.

Did you take into account the additional latent heat of condensation consumed to make that bigger puddle (high humidity day) of water (from water molecules) under the truck?

Like I said the coil temp would be lower. Are your windows tinted, what direction are you pointed. You said to make it simple. If you are running recirc, after a time, your humidity in the cab will go down. I realize that you are enjoying this, or at least I hope you are, but there is nothing simple about it except that air crossing a coil will pull more heat off of the coil when it contains more water.

Vents temps are lower on a higher humidity day, due to the additional condensate. True, recirc will have a negating effect, but the cab is always being infiltrated with wet air. I agree with the rest of your statements.


I would only point out one other thing. If velocity across the coil remains constant for the 2 scenarios, I am in agreement with you. In the real world, the heavier air is more viscous, and velocity is not constant. These finned coils are very inneficient hydraulicly, since they are built for ht transfer with huge pressure drops (mixing) occuring across them.


Mass air flow is key as you have shown, where the state of the ht transfer mediums do not change. Truth is, that going from a gas to liquid gulps energy, and shows it in the reduction of delta T in the cab.

Well, exford, you are theoretically correct, but from a practical standpoint the effect of humidity on a closed cooling system would be insignificant unless the air temperature was at dewpoint temperature.


Masterp2, I will check the fan configuration and clutch part # on both trucks and let you know what I find. One way I have found to eliminate that cold start roar is to start the engine, let it idle for about one minute, then raise the RPM's to around 1500 by pushing the accelerator for about 20 seconds, let it drop back to normal, put it in gear - and take off. I have yet to hear it roar after doing this.

One way I have found to eliminate that cold start roar is to start the engine, let it idle for about one minute, then raise the RPM's to around 1500 by pushing the accelerator for about 20 seconds, let it drop back to normal, put it in gear - and take off. I have yet to hear it roar after doing this.





Yes, a "normal" attribute of the clutch design. I prefer to call it bad design. The fluid settles in the wrong chamber on shutdown (when heat soaks the bimetal strips) It takes a fair amount of cenripetal force to get it back where it belongs for the new cold conditions. That is why I wanted to know if both trucks have the same clutch. If so, the 6.0 running cooler in the stack is my guess as to why it never "fills" with silicone on shutdown.


Welcome to the forum!Edited by: masterp2