Fan clutch

[SatchMax]

Went on vacation and left my 05 ccdad with the dealer and told them about my trouble I was having with my fan clutch. When pulling my 5th wheel it was in and out all the time as compared to my 02 ccdad. Had less than 1500 miles on the new truck. My son picked the truck up and it has a new clutch but have now pulle the 5th wheel or a load with it yet. The dealer said the clutch was out of calibration and replaced it. Will find out if it is better or worse. What is the code for the Cal. emmisions on a truck, and will it hurt the truck if a larger exhaust is put on this lly motor, and does the new juice help this truck as much as it helped my 02 truck. My son was having the same problem with his clutch and one dealer said there was no problem, but the other dealer replaced it like they did mine. Funny how GM dealers are different. Gotta Love Them Durmaxs.

SatchMax
Lubbock, Texas

[Kennedy]

Personally, I would prefer a more active fan clutch as that is what is NEEDED to keep a good balance. Unfortunately, consumer complaints about noise, loss of power and fuel economy losses threaten to put us right back where we were with the 6.5 engine. On the side of the road. :mad: Let the fan engage already...

[Jim Brzozowski]

When I hear mine come on and the coolant temp starts dropping. Thats a good thing.
If you just absolutely can't stand the sound, you could take the fan off and install electric fans to do the job and set your temp setting where you think they ought to be. I think Summit would probably have something that would work. For me I'll keep what I have. To each his own. If you decide to do that let us know how it turns out.

[mcmonroe]

The trick is to design a cooling stack that will pull enough heat from the cooling system without having to run the fan as often.

When a truck is running down the freeway at 70mph there is *plenty* of air pushing on the front of the truck to keep it cool without the fan running if the cooling stack is big enough. In fact I would argue that the fan doesn't move much additional air at those speeds.

When I am driving an almost $50,000 truck with passengers and the fan comes on and all of them say "What the hell is wrong with your truck" -- I think we have a clear sign that the cooling system is poorly designed. Surely those GM engineers are smart enough to give us an effective cooling stack without taking the easy way out and having the fan run all the time.

The bottom line? Put bigger radiators in the truck and design a front end that allows plenty of air flow.

Random thoughts...

Mark

[rjschoolcraft]

That's counterproductive to good aerodynamics and fuel mileage...

Your assumption that the fan will not move that much more air when running 70 mph is not accurate either. Test data is a good thing. Some folks tend to ignore it, though.

[JD Diesel]

I have noticed that mine runs along time when I first start it in the morning is this normal. :confused: Dont really care that it comes on when its hot I just know that it is protecting its self which is great better early than late Right. ;) JD

[Kennedy]

From the fan clutch engagement thread:


Originally posted by More Power:
In addition to what DmaxMaverick mentioned:

Due to the fluid settling characteristics, these fan-clutches usually engage after the engine has been shut-off for a time - whether overnight or several hours. The fan-clutch will disengage after a half mile or so of driving. This is normal.

A thermostatic coil on the front of the fan-clutch controls engagement while the engine is running, and will react to changes in heat felt by the coil. The Allison ATF cooler, A/C condenser, intercooler and radiator all add heat to the airflow entering the engine compartment through the grille. Once the temperature reaches a predetermined level, the thermostatic coil on the fan-clutch will engage the fan.
MP Personally, coming from a 6.5 that had heating issues (until we built our special calibration fan clutch) I like to hear the clutch come in. My 2002 engaged the clutch several times driving empty from Missoula (DP Rend.) to Denver (ATS) two years back. My LLY lets the temp get much warmer and seldom (if ever)engaged on flat ground towing 11k+ in 90

[a bear]

The transmission cooler dumps a lot of heat right in the center of the stack and the front of the fan clutch. Moving the transmission cooler has completely eliminated my interstate travel fan clutch activity. Previously I would see engaugement about every 5 mins while towing. Now it's completely gone and the engine temp stays lower when pulling steep grades. Another added benefit is much cooler AC since the coils no longer has a cooler in front dumping heat into it. Should improve on intercooler temps also.

[Ofbmicsafety]

Just got back from a 3 week trip to Yellow Stone! Should have stayed there. On a mild grade out of Riverton Wy following a friend with a 34 foot fiver my LLY got up to the middle mark between 210 and 260. (ambent temp outside was 102) I assume that means it was running around 235. My trailer is only a 27 fiver. Friend was driving an 03 F**d. Said his temp never moved. Had simular problems when the outside temps were in the mid 80's. One time temp got as high as 240 and yes the fan was screaming. I do not hot rod my LLY going up grade. Try to keep RPM around 2200-2500 to help with the fan air flow. Is this normal for the LLY to get this hot? Never had a problem with my 02 or 03 getting that hot or my 99, 00 or 01 F**d. Hate to take it to the dealer they had my 02 for 23 days while I tried to convince them it was the injectors. IT WAS! So how hot is too hot and any suggestions would be appreciated.

[SatchMax]

MY DEALER SAID MY FAN WAS OUT OF CALIBRATION AND PUT A NEW ONE IN. HAVE NOT PULLED MY 5ER YET BUT CAN TELL THAT IT IS NOT IN AND OUT LIKE IT WAS BEFORE I TOOK IT INTO THE DEALER. THIS LAST SAT THE TEMP WAS AROUND 98 AND THE ONLY TIME IT CAME IN WAS STOPING AT RED LIGHTS AND WOULD GO OUT BY THE TIME I GOT UP TO SPEED AGAIN. WILL LET YOU KNOW WHEN I PUT THE 5ER ON OR PULL THE FLAT BED TRAILER WITH THE JD TRACTOR. THEY DID THE SAME THING TO MY SONS 03 AND HIS IS WORKING FINE RIGHT NOW. WILL LET YOU KNOW LATER
SATCHMAX
LUBBOCK, TEXAS

[More Power]

It would appear that GM raised the fan-clutch engage temperature to reduce the number of warranty concerns about fan noise that were mistaken for something abnormal.

The LLY runs with a new VNT (variable nozzle turbo) and more aggressive EGR, when compared to the LB7. These and possibly other programming changes apparently allow the engine to run warmer than the LB7 when worked hard.

Personally, I think raising the fan-clutch engage temp was a bad idea. The fan-clutch is an often overlooked but critical component in the engine cooling system. We also know from our 6.5 experience that a late engaging fan-clutch is behind the curve, when trying to control or reduce engine temperatures (harder to catch up when engaging late). It's best to be ahead of the curve, and the LB7 was definitely ahead of the curve with frequent fan-clutch engagement. My LB7's temperature gauge never moves when pulling hills in 100+ summer temps with a trailer in tow.

MP

[markrinker]

I agree. Would rather have the fan coming on early, rather than after I see my water temps hitting critical mass...

I noticed the fan clutch engaging yesterday pulling the same boat through the same hills home from the lake.

Only difference was the ambient temp outside - about 90 degrees. Engine water temp never exceeded 200, tranny temp stayed normal. A/C was on max the whole time.

Seemed to work well for the circumstances. It is loud!

[REDTRUCK05]

I SWITCHED FROM A FORD 7.3 2 A GM 6.6 BECAUSE IT WAS A BETTER RIDE AND QUITER WITH THE FAN NOISE IT IS UPSETTING!

[rjschoolcraft]

Let me guess, the Ford fan was whisper quiet, yet moved 300,000 CFM...

[Kennedy]

For those complaining about fan enagement, loss of power/mpg you can go to the dealer like some are and get it condemned as out of spec (they have a 10 degree window to the calibration) and replaced.

Now I'm not trying to sound rude, but when you start running hot and overheating under heavy load I'm going to say I told you so.

The LLY does seem to generate more heat, but should be controllable. I find that my LLY will idle up to temp much more quickly than my LB7 which is likely an emissions thing. As emissions get tighter, you'll see changes in heat rejection to gain compliance...

[REDTRUCK05]

Originally posted by ronniejoe:
Let me guess, the Ford fan was whisper quiet, yet moved 300,000 CFM... NO, COULD NOT SAY THAT THE FORD WAS WHISPER QUIET, BUT THE FAN NEVER CAME ON. ALL I HEARD WAS WAS NOISE OF THE ENGIME. MY 6.6 LLY WAS COMMING ON FOR 7-10 MIN AT A TIME. I BROUGHT IT TI THE DEALER AND THEY REPLACED THE FAN FOR FREE, HAVE NOT PULLED WITH IT SINCE BUT WILL MAKE A POSTING WHEN I DO WITH THE RESULTS IF ANY.

[rjschoolcraft]

Originally posted by REDTRUCK05:
NO, COULD NOT SAY THAT THE FORD WAS WHISPER QUIET, BUT THE FAN NEVER CAME ON. ALL I HEARD WAS WAS NOISE OF THE ENGIME. MY 6.6 LLY WAS COMMING ON FOR 7-10 MIN AT A TIME. I BROUGHT IT TI THE DEALER AND THEY REPLACED THE FAN FOR FREE, HAVE NOT PULLED WITH IT SINCE BUT WILL MAKE A POSTING WHEN I DO WITH THE RESULTS IF ANY. With as loud as the 7.3 is, how would you ever know if the fan came on? :rolleyes:

The point is this. I'm a 6.5 driver. The 6.5's have been notorious about overheating. In fact, Kennedy had a specially calibrated fan clutch made to engage 15 degrees cooler than the stock unit. I have one, it engages a lot more than the other one, but now I don't run hot anymore.

Many of you guys who complain about the fan clutch engaging are the very same ones who complain about overheating. Your silliness about the fan clutch is going to drive you right into the same problems that the 6.5 had...blown corks on the side of the road.

I personally relish the sound of the fan coming on in my truck because I know now that I won't have to pull over to let the engine cool back down on long grades.

The fan is there to move air. If you need to move a lot of air, it will make noise. Just listen to a modern turbofan... The Duramax is so much quieter than the competition that you can actually hear the fan. That's still not as loud as the 7.3's or the 2002 and previous Cummins...

[Tough Guy]

Easy there Ron....we're all friends here.

Having driven an LB7 quite a bit, pulling/loaded etc..the fan clutch works rather nicely...and as expected. Temps do NOT fluctuate at all.

Having riden in several LLY's pulling/loaded etc..the fan clutch engages late and often. Temps are much higher then compared to the LB7...

I own a 7.3L, at idle they are much louder than 6.5L's or 6.6L's but at cruising speed appreciably quieter. You can hear the fan clutch engage, and it is seemingly less often then the LLY or LB7...Why? I have no idea. The ECT needle never moves either.

I do know that the intercooler pipes for the LB7 and the 7.3L look nearly identical, rather large...and the LLY pipes look tiny in comparison...

I also own and drive daily a 6.5L and on hot days (90F+) the fan clutch is engaged all day long...

So the moral of my long post is, don't worry about your fan clutch, its good a thing...regardless of what you drive.

Cheers

[REDTRUCK05]

Originally posted by Tough Guy:
Easy there Ron....we're all friends here.

Having driven an LB7 quite a bit, pulling/loaded etc..the fan clutch works rather nicely...and as expected. Temps do NOT fluctuate at all.

Having riden in several LLY's pulling/loaded etc..the fan clutch engages late and often. Temps are much higher then compared to the LB7...

I own a 7.3L, at idle they are much louder than 6.5L's or 6.6L's but at cruising speed appreciably quieter. You can hear the fan clutch engage, and it is seemingly less often then the LLY or LB7...Why? I have no idea. The ECT needle never moves either.

I do know that the intercooler pipes for the LB7 and the 7.3L look nearly identical, rather large...and the LLY pipes look tiny in comparison...

I also own and drive daily a 6.5L and on hot days (90F+) the fan clutch is engaged all day long...

So the moral of my long post is, don't worry about your fan clutch, its good a thing...regardless of what you drive.

Cheers Its noisy and costs fuel. I am just wondering in what way in 2006 they changed the system and it does not NEED to engage nearly as often(so I have read)just as the early lb7 and the 7.3. I guess I am not looking for sarcasm just constructive input.

[REDTRUCK05]

Originally posted by REDTRUCK05:
</font><blockquote>quote:</font><hr />Originally posted by Tough Guy:
Easy there Ron....we're all friends here.

Having driven an LB7 quite a bit, pulling/loaded etc..the fan clutch works rather nicely...and as expected. Temps do NOT fluctuate at all.

Having riden in several LLY's pulling/loaded etc..the fan clutch engages late and often. Temps are much higher then compared to the LB7...

I own a 7.3L, at idle they are much louder than 6.5L's or 6.6L's but at cruising speed appreciably quieter. You can hear the fan clutch engage, and it is seemingly less often then the LLY or LB7...Why? I have no idea. The ECT needle never moves either.

I do know that the intercooler pipes for the LB7 and the 7.3L look nearly identical, rather large...and the LLY pipes look tiny in comparison...

I also own and drive daily a 6.5L and on hot days (90F+) the fan clutch is engaged all day long...

So the moral of my long post is, don't worry about your fan clutch, its good a thing...regardless of what you drive.

Cheers Its noisy and costs fuel. I am just wondering in what way in 2006 they changed the system and it does not NEED to engage nearly as often(so I have read)just as the early lb7 and the 7.3. I guess I am not looking for sarcasm just constructive input. </font>[/QUOTE]Sorry that last bit wasnt towards you

[rjschoolcraft]

I know it was aimed at me, and that's ok. I was being sarcastic...to make a point. The fan is there to do a job...move air.

In the world of Diesel, tighter emissions means more heat generation. Been through when I worked for Caterpillar and it's happening with the Duramax (and with the other guys as well). The fan on the lower emissions trucks will run more if nothing else changes.

I hate to hear people gripe about fan clutches engaging because of the cooling system problems that have plagued the 6.5. I don't want to see the Duramax have to deal with the same issues because of complaints about noise.

Larger radiators (as suggested in another post) would help, but that runs counter to the clean aerodynamics that we enjoy on the newer trucks. The Ford and Dodges are not nearly as clean as the Chevy/GMC.

Frankly, your reported mpg numbers sound low compared to many others that I know of. You may have a specific problem that should be addressed. Heck, with my old 6.5, I get 8 mpg towing at 75 with a 32' Wilderness TT weighing in at 9,000 lb. Nearly every DMax owner I've ever talked to does better than that.

[SatchMax]

My son just returned from a 800 mile trip pulling his fifth wheel with the new fan clutch. I ask his about it going down and he said it never came on and the truck ran fine. Coming back it would come on but nothing like it did before he had it changed and the temp never got above 210 and the temp outside was over 95. I have not pulled anything with my 05 yet but will tell You when I do. If the temp guage was getting up to 220 or 230 and I would expect the clutch to engage. When it never goes above 210 and raising all kinds of heck then I think there is a problem with the clutch or the temp guages are not worth anything. My 02 and my other sons 01 never had the problem that the 03 and 05 were having before we took them and got them replaced. Our chev dealer said other people had been in with the same problem and once they replace it the customer never complained again. May be quaility control in the fan clutch.
SatchMax
Lubbock, Texas

[Kennedy]

The fan clutch on my 02 runs more often than my 05. The 02 maintains cooler temps while the 05 has seen elevated ECT (220-230) on hills at elevation.

I'd rather have a more active fan and lower coolant/oil temps. It does not take a ton of HP to drive these fans.

I will not likely see any extreme heat like we did towing out west, but I have recently changed the fan clutch on my 2005 and will see how it goes...

[LanduytG]

I own a 7.3L, at idle they are much louder than 6.5L's or 6.6L's but at cruising speed appreciably quieter Chris
You can't be serious about the 7.3 being quieter than a Dmax? I have been around a lot of 7.3's and not one of them was quieter than a Dmax.

Greg

[REDTRUCK05]

Originally posted by kennedy:
The fan clutch on my 02 runs more often than my 05. The 02 maintains cooler temps while the 05 has seen elevated ECT (220-230) on hills at elevation.

I'd rather have a more active fan and lower coolant/oil temps. It does not take a ton of HP to drive these fans.

I will not likely see any extreme heat like we did towing out west, but I have recently changed the fan clutch on my 2005 and will see how it goes... My father in law runs a 2001 3500 6.6LB7. His fan only engauges in the mountains or like conditions. I just had the shop replace mine and it made no change. What I do not understand is my gauges never change! before or after. tranny is at 190 engine is at 210.

[REDTRUCK05]

Originally posted by LanduytG:
</font><blockquote>quote:</font><hr />I own a 7.3L, at idle they are much louder than 6.5L's or 6.6L's but at cruising speed appreciably quieter Chris
You can't be serious about the 7.3 being quieter than a Dmax? I have been around a lot of 7.3's and not one of them was quieter than a Dmax.

Greg </font>[/QUOTE]I dont think I said quiter, If I did let me refraise... the fan never needed to come on because of design. I pulled my trailer fully loaded, truck full of firewood, water and my kids and wife to Mt rushmoore. It downshifted 4 times the whole way (except the final 30 miles or so) and going 70-75 got 13-14 mpg fan never came on. Dont get me wrong, I like my truck I guess I just need to get used to the fan and the lower mpg.

[Tough Guy]

Originally posted by LanduytG:
</font><blockquote>quote:</font><hr />I own a 7.3L, at idle they are much louder than 6.5L's or 6.6L's but at cruising speed appreciably quieter Chris
You can't be serious about the 7.3 being quieter than a Dmax? I have been around a lot of 7.3's and not one of them was quieter than a Dmax.

Greg </font>[/QUOTE]Greg,

I can see how my statement could be mis-understood. I do not think the 7.3L is quieter than the Dmax at all. What I meant to say was that the 7.3L is much quieter at cruising than one would expect considering the db's at idle...

Cheers

[LanduytG]

Tough Guy
OK I can agree with that statement :D ..
Greg

[Kennedy]

Originally posted by REDTRUCK05:


My father in law runs a 2001 3500 6.6LB7. His fan only engauges in the mountains or like conditions. I just had the shop replace mine and it made no change. What I do not understand is my gauges never change! before or after. tranny is at 190 engine is at 210. Consider yourself lucky that you are not seeing 220-230+ and be prepared if you hit the higher elevations. I can only hit 203

[REDTRUCK05]

Originally posted by ronniejoe:
I know it was aimed at me, and that's ok. I was being sarcastic...to make a point. The fan is there to do a job...move air.

In the world of Diesel, tighter emissions means more heat generation. Been through when I worked for Caterpillar and it's happening with the Duramax (and with the other guys as well). The fan on the lower emissions trucks will run more if nothing else changes.

I hate to hear people gripe about fan clutches engaging because of the cooling system problems that have plagued the 6.5. I don't want to see the Duramax have to deal with the same issues because of complaints about noise.

Larger radiators (as suggested in another post) would help, but that runs counter to the clean aerodynamics that we enjoy on the newer trucks. The Ford and Dodges are not nearly as clean as the Chevy/GMC.

Frankly, your reported mpg numbers sound low compared to many others that I know of. You may have a specific problem that should be addressed. Heck, with my old 6.5, I get 8 mpg towing at 75 with a 32' Wilderness TT weighing in at 9,000 lb. Nearly every DMax owner I've ever talked to does better than that. Thanks for the input, This is what I wanted to hear. I talked to the shop manager and he is going to check the computer after we get home from vacation. I will let you guys know what I find...

[SatchMax]

Finally made a trip pulling my 32ft fifth wheel trailer. Going up I27 with temp outside at 90 degrees my fan would come on every 3.5 miles and not go out for 3.5 miles. The clutch was not as loud as it was before they change it out, but it was in and out every 3.5 miles. The motor temp was on the left of 210 and trans was at 190 everytime it came on and went off. Also the wind was pushing my truck and trailer. Today when we returned the outside temp was 65 and motor temp was at 210 straight up or barely to the right of 210 and the trans was running at 170 or 180 and the fan never engaged at 70 to 75 miles per hour. Going up the truck showed 9.1 mpg and today it showed 10.1 coming back with the wind pushing us again. Wondering if the edge would help and also if the larger exhaust would help with this problem. Truck has 3500 miles on it. We camped out in Palo Duro canyon and going in and out there is a 10.5% grade and the truck handled it very well. Coming out with a lot of horse shoe curves and slow speed the lly ccda dually did not waste any time coming up the 10.5% grade.
SatchMax
Lubbock, Texas

[rjschoolcraft]

Doesn't really sound like you have a problem at all...

[Kennedy]

Opening the exhaust and adding some more grunt should help your situation by keeping you in the lower RPM power band with less pedal input. Exhaust temps should drop a good bit, especially if the cat disappears...

[ 08-17-2005, 05:00 AM: Message edited by: kennedy ]

[REDTRUCK05]

Originally posted by kennedy:
Openiong the exhaust and adding some more grunt should help your situation by keeping you in the lower RPM power band with less pedal input. Exhaust temps should drop a good bit, especially if the cat disappears... Can I ask what the cat is? Or did I miss something?

[REDTRUCK05]

Originally posted by SatchMax:
Finally made a trip pulling my 32ft fifth wheel trailer. Going up I27 with temp outside at 90 degrees my fan would come on every 3.5 miles and not go out for 3.5 miles. The clutch was not as loud as it was before they change it out, but it was in and out every 3.5 miles. The motor temp was on the left of 210 and trans was at 190 everytime it came on and went off. Also the wind was pushing my truck and trailer. Today when we returned the outside temp was 65 and motor temp was at 210 straight up or barely to the right of 210 and the trans was running at 170 or 180 and the fan never engaged at 70 to 75 miles per hour. Going up the truck showed 9.1 mpg and today it showed 10.1 coming back with the wind pushing us again. Wondering if the edge would help and also if the larger exhaust would help with this problem. Truck has 3500 miles on it. We camped out in Palo Duro canyon and going in and out there is a 10.5% grade and the truck handled it very well. Coming out with a lot of horse shoe curves and slow speed the lly ccda dually did not waste any time coming up the 10.5% grade.
SatchMax
Lubbock, Texas Sounds like a good road trip! Sounds like you are happy with the power. How about the mpg? How heavy is your trailer? I am leaving for vacation on friday pulling a 7000lb travel trailer. I was having issues with the fan also, had it replaced. I will let you guys know what happens.

[dmax lover]

Mr Kennedy,
How goes your initial testing of your prototype fan clutch for the lly?

I was wondering whether all the "stack sealing" going on elsewhere is just making up for a fan that is "underactive" at low engagement?

jeff

[SatchMax]

REDTRUCKS05
Our Open Road 5er weights around 11000. Was going to have the truck and trailer weighted Sunday afternoon but it was raining. We got 9.1 going up and 10.1 coming back. Temp was 95 going up there and 65 coming back and running 70 to 75 both ways. No problem pulling the trailer and the truck would have pulled it a lot faster if You want it to. Let us know how the fan works on this trip. As JK said I might need more grunt and get rid of the cat. Going to be working on that problem.
Have a great and save trip.
SatchMax
Lubbock, Texas

[Kennedy]

dmax lover,

I have an RV hauler running a clutch that I sent him to see how it does. The LLY does seem to transfer more heat to the coolant plain and simple so I doubt that we'll see it run as cool as the LB7, but you never know. I'd like to see it dropped to 210

[J-M]

JK, I am running a 4500 LLY and is running hot,real hot when towing. Took to dealer ,they replaced the fan clutch.Saw some temp decrease as the fan ran more often.Just seems the fan is behind the heat curve and can not catch up.If stack sealing was sutch an issue on the light trucks why are the bigger trucks doing it also.If youre clutch works I will buy one now.

[Kennedy]

I've got one out in testing and one on my LLY. That's all I could scrounge so far w/o a major commitment. The unit in the field is just beginning the test.

I should note that fan clutch engagement calibrations run in a 10

[J-M]

I can deal with a 10 deg window, just cant deal with temps over 230.I even got ride of the Dex coll for the Evens coolant.Saw no change. I will buy your clutch pronto if it works. Thank you for your time.

[Showgood1]

I helped a friend change a water pump on his truck yesterday. This was the first time I had gotten to see the radiator out of one of these trucks and I don't think it is any bigger than the one on my big block. Also I was wondering my 454 has a auxillary electric fan from the factory. Would it be worth it to add one (big one or two small ones) on the Dmax to at least delay or in some cases eliminate the fan clutch kicking in? I'm not talking about replaceing the big fan just adding a electric to suppliment it. More horses more MPG?

[jwlbal]

I just looked at a 2006 on a dealer lot today and was surprised to see that the cooling stack has been changed. Without comparing it directly to my 2004, I think the main difference is the transmission cooler has been moved lower to allign with the opening in the bumper. Or it could just look different, due to a different mesh design on the grille...

[Dave]

Originally posted by kennedy:
From the fan clutch engagement thread:

</font><blockquote>quote:</font><hr />Originally posted by More Power:
[b] In addition to what DmaxMaverick mentioned:

Due to the fluid settling characteristics, these fan-clutches usually engage after the engine has been shut-off for a time - whether overnight or several hours. The fan-clutch will disengage after a half mile or so of driving. This is normal.

A thermostatic coil on the front of the fan-clutch controls engagement while the engine is running, and will react to changes in heat felt by the coil. The Allison ATF cooler, A/C condenser, intercooler and radiator all add heat to the airflow entering the engine compartment through the grille. Once the temperature reaches a predetermined level, the thermostatic coil on the fan-clutch will engage the fan.
MP Personally, coming from a 6.5 that had heating issues (until we built our special calibration fan clutch) I like to hear the clutch come in. My 2002 engaged the clutch several times driving empty from Missoula (DP Rend.) to Denver (ATS) two years back. My LLY lets the temp get much warmer and seldom (if ever)engaged on flat ground towing 11k+ in 90

[Dave]

Originally posted by Tough Guy:
Easy there Ron....we're all friends here.

Having driven an LB7 quite a bit, pulling/loaded etc..the fan clutch works rather nicely...and as expected. Temps do NOT fluctuate at all.

Having riden in several LLY's pulling/loaded etc..the fan clutch engages late and often. Temps are much higher then compared to the LB7...

I own a 7.3L, at idle they are much louder than 6.5L's or 6.6L's but at cruising speed appreciably quieter. You can hear the fan clutch engage, and it is seemingly less often then the LLY or LB7...Why? I have no idea. The ECT needle never moves either.

I do know that the intercooler pipes for the LB7 and the 7.3L look nearly identical, rather large...and the LLY pipes look tiny in comparison...

I also own and drive daily a 6.5L and on hot days (90F+) the fan clutch is engaged all day long...

So the moral of my long post is, don't worry about your fan clutch, its good a thing...regardless of what you drive.

Cheers I had a 01 LB7 truck, pulled 12,000 pounds with it very frequently, a Big square RV. Temperature gage almost never moved, clutch fan almost never engaged except on a mountain grade and out side temps in the high 90's.

My 05 LLY truck exact same as 01 except engine, the fan runs 50% of the time pulling a 4000 pound V nose motorcycle trailer much more aero dynamic than the RV. Tempurature gage moves up and down more. Fan comes on in high 70 degree weather flat road pulling 4000 pounds which should be nothing.

To me the LB7 had a very good and efficient cooling system that worked as it should. The LLY had an inefficient cooling sytem that is not up to the job, allows the truck to get to hot and fan must run to much. :eek:

[REDTRUCK05]

[quote]Originally posted by kennedy:
[b] I've got one out in testing and one on my LLY. That's all I could scrounge so far w/o a major commitment. The unit in the field is just beginning the test.

I should note that fan clutch engagement calibrations run in a 10

[Kennedy]

The clutch that I sent out aoppears to be helping some of the time. The problem is, it is just as erratic as the one that came on his truck. The truck can still get hot. I have one on my LLY, but am not sure if we'll see much heat enroute to Weekend One the Edge/DP Rendezvous.

Nice talking to you. Feel free to call any time, but be prepared to get the voice mail. I can always call you back.

[REDTRUCK05]

Originally posted by ronniejoe:
That's counterproductive to good aerodynamics and fuel mileage...

Your assumption that the fan will not move that much more air when running 70 mph is not accurate either. Test data is a good thing. Some folks tend to ignore it, though. AND THE FAN ENGAGEING ALL THE TIME DUE TO POOR DESIGN DOES NOT COST FUEL AND HP? IT WAS A POOR DESIGN THATS WHY THEY CHANGED IT IN 2006! END OF STORY

[rjschoolcraft]

Originally posted by REDTRUCK05:
</font><blockquote>quote:</font><hr />Originally posted by ronniejoe:
That's counterproductive to good aerodynamics and fuel mileage...

Your assumption that the fan will not move that much more air when running 70 mph is not accurate either. Test data is a good thing. Some folks tend to ignore it, though. AND THE FAN ENGAGEING ALL THE TIME DUE TO POOR DESIGN DOES NOT COST FUEL AND HP? IT WAS A POOR DESIGN THATS WHY THEY CHANGED IT IN 2006! END OF STORY </font>[/QUOTE]IS YOUR CAPS LOCK STUCK? ARE YOU YELLING AT ME?

I don't think it's the end of the story. If you had ever dealt with overheating problems because of late engagement of a fan clutch, as I have, you would not complain so much. The Kennedy aftermarket clutch that I have on my 6.5 engages frequently, even in the winter when towing. It is music to my ears because now I don't overheat.

My comments were directed as a response to the following quote:


Originally posted by Mark Monroe:
The bottom line? Put bigger radiators in the truck and design a front end that allows plenty of air flow.
Putting bigger radiators in the truck means more frontal area. That means more drag. What I said in that quote is true, no matter how out of context you want to take it.

You don't want the fan to ever come on...that's not realistic. And as I said previously, you will wind up right where the 6.5 has been...boiling down on the side of the road.

The LB7 cooling system was well engineered. I've never heard of an overheating problem on an LB7 truck. The fan does engage sometimes and people have complained about it. GM reacts by delaying fan clutch engagement on the LLY to prevent the "noise problem". Coupled with that, the aerodynamic requirements dictated a change in the grill opening and the emissions requirements dictated an increase in heat load. That's a recipe for disaster, based on ill-informed customer complaints.

I wish you well with your truck. Hopefully you will get it "fixed" to your satisfaction and it will not overheat on you. If not, you can always go back to the Ford...

I apologize that my first post in this thread was dripping with sarcasm. I was simply trying to make a point. It apparently offended you and I am sorry.

[lookin2buy]

Have any of you experienced sitting on the side of the road with steam rolling out of the hood? I understand with the 6.5's but with the 2001-present I haven't read about any on here. Also, i understand the 2006's have been only out a month on the lots... just woundering if anyone has had towing experience with them yet.

Just curious! smile.gif

[Kennedy]

Some of the LLY owners have reported reduced power mode/warning light and having to stop. I haven't experienced this, but will say that in the dry climate of the plains and hills of WY, UT, and MT my LLY runs warm. Not overheating, but warm. Back home it stabilizes nicely...

Coming back from UT the Attitude monitor did record 223

[REDTRUCK05]

Originally posted by ronniejoe:
</font><blockquote>quote:</font><hr />Originally posted by REDTRUCK05:
</font><blockquote>quote:</font><hr />Originally posted by ronniejoe:
That's counterproductive to good aerodynamics and fuel mileage...

Your assumption that the fan will not move that much more air when running 70 mph is not accurate either. Test data is a good thing. Some folks tend to ignore it, though. AND THE FAN ENGAGEING ALL THE TIME DUE TO POOR DESIGN DOES NOT COST FUEL AND HP? IT WAS A POOR DESIGN THATS WHY THEY CHANGED IT IN 2006! END OF STORY </font>[/QUOTE]IS YOUR CAPS LOCK STUCK? ARE YOU YELLING AT ME?

I don't think it's the end of the story. If you had ever dealt with overheating problems because of late engagement of a fan clutch, as I have, you would not complain so much. The Kennedy aftermarket clutch that I have on my 6.5 engages frequently, even in the winter when towing. It is music to my ears because now I don't overheat.

My comments were directed as a response to the following quote:


Originally posted by Mark Monroe:
The bottom line? Put bigger radiators in the truck and design a front end that allows plenty of air flow.
Putting bigger radiators in the truck means more frontal area. That means more drag. What I said in that quote is true, no matter how out of context you want to take it.

You don't want the fan to ever come on...that's not realistic. And as I said previously, you will wind up right where the 6.5 has been...boiling down on the side of the road.

The LB7 cooling system was well engineered. I've never heard of an overheating problem on an LB7 truck. The fan does engage sometimes and people have complained about it. GM reacts by delaying fan clutch engagement on the LLY to prevent the "noise problem". Coupled with that, the aerodynamic requirements dictated a change in the grill opening and the emissions requirements dictated an increase in heat load. That's a recipe for disaster, based on ill-informed customer complaints.

I wish you well with your truck. Hopefully you will get it "fixed" to your satisfaction and it will not overheat on you. If not, you can always go back to the Ford...

I apologize that my first post in this thread was dripping with sarcasm. I was simply trying to make a point. It apparently offended you and I am sorry. </font>[/QUOTE]I was not yelling at you, simply a case of not wanting to pay attention to grammer syntax. First off, you say the LB7 was well engineered? Thats my point exactly. If the GM Engineerers are going to base their design after complaints on this or any other forum then I and we should think twice about buying another truck. You say it is music to your ears to hear that fan come on? Well I see that as a result of a victim of a poor design willing to put up with another poor design because it solved the first one. As far as Kennedys fan, God bless him! He should be a GM Engineer. I still say with the design of the front end and the proper design of the cooling system, there is no reason for the fan to engauge unless under HEAVY load. As far as your comment of being able to go back to a ford? Hmmm...

[More Power]

Engine temperature is one of at least four contributors in determining fan-clutch engagement.

Engine temperature
A/C condenser
Intercooler
Transmission ATF cooler

Could the Garrett VNT turbo and more aggressive EGR used in the LLY be part of the puzzle?

Jim

[rjschoolcraft]

Originally posted by More Power:
Engine temperature is one of at least four contributors in determining fan-clutch engagement.

Engine temperature
A/C condenser
Intercooler
Transmission ATF cooler

Could the Garrett VNT turbo and more aggressive EGR used in the LLY be part of the puzzle?

Jim You bet!

[markrinker]

For what its worth, my 2005 LLY has been towing hard since day one, a little over two months ago.
14K towing miles and the fan clutch seems to be working properly. It comes on about 210 and brings temps back down to 190 or so before it disengages.

Personally, I LOVE the sound. Nothing better.

We are on week two with a new/used 2001 LB7. Seems to run a bit cooler, but fan seems 'busier' than on the LLY. Too early to compare, however.

Again, the fan roaring sound is normal to me - and is daily occurance since we always tow. I think of it as an audible reminder to check gauges - and maybe slow down a bit.

JK I am interested in your idea regarding improved underhood airflow. The 2005 is very very hot under the hood. Good in the winter, bad in the summer.

Seems like you could vent that big 'cowl induction' looking hood and do some good for underhood temps. Or maybe run something like this in the summertime, returning to the stock hood in the wintertime.

http://www.gmcpauls.com/pictures/Cowl%20Hoods/03-04%20Chevy%20Silverado,%20Avalanche%20Ram%20Air.jp g

(Knowing my luck, the ram air effect would slow down airflow through the cooling stack, and water temps would rise...)

[ 09-19-2005, 05:28 AM: Message edited by: Mark Rinker ]

[Kennedy]

Cowl induction could push us in reverse unless cowl air is restricted to the air intake system.

I believe the key is to evacuate underhood air underneath the vehicle...

[markrinker]

I wonder if there are heating differences between trucks equipped with skid plates, and those that aren't?

[Dave]

[quote]Originally posted by kennedy:
[b] Some of the LLY owners have reported reduced power mode/warning light and having to stop. I haven't experienced this, but will say that in the dry climate of the plains and hills of WY, UT, and MT my LLY runs warm. Not overheating, but warm. Back home it stabilizes nicely...

Coming back from UT the Attitude monitor did record 223