engine cooling

[macmac]

This is a question about my truck's cooling systems …

I have a Silverado, 1 ton dually, Duramax/Allison powertrain, new in 2004, standard specification for towing.  It hauls a 13,000lbs fifth wheel.

When it’s working hard on tow I hear various fan noises.  These increase in intensity and speed as the  engine gets hot but I’ve never been able to figure what fan is making what noise.  I can see a large diameter, viscous-coupled fan behind the two closely mounted large radiators and that’s all.  I can hear that kick in and out, speed varying according to the gear I’m in.

So what other fans (if any) can I hear and what causes their speed to increase markedly under heavy load sometimes – the turbo intercooler?

Lastly, towing up Wolf Creek Pass, CO, on a recent hot day I found the limit of the cooling sytem.  Close to the summit I could see the engine coolant temperature was getting close to the gauge red sector.  Literally as I pulled off the highway to allow the engine to cool, the engine management system indicated a coolant overheat warning.  A few minutes parked in ‘P’ with the engine at around 1500rpm cooled the system to near normal but the transmission temperature indication didn’t budge.

Luckily I was only a half mile from the summit and as we descended the transmission quickly cooled too.

 But why didn’t the main fan cool that along with the engine coolant?

[crosscountry]

When you over heat turn your heater on full blast, set to high heat.  These circulates the water and cools it off somewhat. It may be a bit hot and stuffy but it works.

I may be way off base but I had a noise in our Explorer that sounded like the fan was rubbing the radiator.  It turned out to be the timing belts.

Russ

[macmac]

When you over heat turn your heater on full blast, set to high heat.  These circulates the water and cools it off somewhat. It may be a bit hot and stuffy but it works.

I may be way off base but I had a noise in our Explorer that sounded like the fan was rubbing the radiator.  It turned out to be the timing belts.

Russ

Yes I can see that would help a little but we'd already turned off the a/c and the outside temperature was high 80s - blowing hot air would have killed us unless we stood outside the cab - in the Colorado sunshine!.... 

I'll keep that in mind for next time, though.  It should help with the engine cooling but what of the transmission?

The only noises I hear are increasing and decreasing fan speeds.  All the mechanicals look fine.

[crosscountry]

Your right it does get hot.  We did it going across desert in July.  We did not want to sit there to cool down. 
With the heater on and somewhat cooling the radiator the transmission cooler should help cool the transmission.  It is not a cure all but should get you down the road so you don't have to stop.

Sorry, not familiar enough with you engine to help with the fan noise.

This is not related to you fan noise.  However, when I overheated on hills I had a stuck thermostate, cracked manifold and once a clogged radiator.

Hope you find your answer soon.

Russ

[Marsha/CA]

macmac,

We have a 2007 Chevy 3/4 ton diesel and yes, the fans get very loud. 

Don't hold me to the specifics of my information; but before we bought our truck, I had been watching the Silverado- duramax-allison truck for a few years.  I had a 93 Chevy gas 1 ton dually and was thinking of getting a new truck; but we try to not buy the first year of drastic change in cars/trucks.  I'm an intense researcher and at one point in my research, I recall there was a year 2003 ?-2004 ? where the duramax was overheating while pulling a load up a grade.  It didn't do it without a load.  I think it had to do with size of the radiator or the size of the fan.  There was a fix and in subsequent years the problem was resolved; but I held off buying until that got solved.

Don't know if this helps, but perhaps you can check it out.

Marsha~

[macmac]

macmac,

We have a 2007 Chevy 3/4 ton diesel and yes, the fans get very loud. 

Don't hold me to the specifics of my information; but before we bought our truck, I had been watching the Silverado- duramax-allison truck for a few years.  I had a 93 Chevy gas 1 ton dually and was thinking of getting a new truck; but we try to not buy the first year of drastic change in cars/trucks.  I'm an intense researcher and at one point in my research, I recall there was a year 2003 ?-2004 ? where the duramax was overheating while pulling a load up a grade.  It didn't do it without a load.  I think it had to do with size of the radiator or the size of the fan.  There was a fix and in subsequent years the problem was resolved; but I held off buying until that got solved.

Don't know if this helps, but perhaps you can check it out.

Marsha~

Thanks Marsha - interesting observations.  I'll see if I can locate any information online.  I've never had trouble when not towing but an engine this big doesn't work very hard without a heavy load.

I guess I might also ask whether towing my trailer load, on a grade as steep as that was, at ambient temperatures as high as on that day, is actually outside the drive train's operating parameters? 

At some point a combination of all those factors would push the system beyond the limits at which it can safely operate.

The question I might have asked is would it be likely that the unit was working close to its maximum designed rating on that day? 

[macmac]

Your right it does get hot.  We did it going across desert in July.  We did not want to sit there to cool down.  
With the heater on and somewhat cooling the radiator the transmission cooler should help cool the transmission.  It is not a cure all but should get you down the road so you don't have to stop.

Sorry, not familiar enough with you engine to help with the fan noise.

This is not related to you fan noise.  However, when I overheated on hills I had a stuck thermostate, cracked manifold and once a clogged radiator.

Hope you find your answer soon.

Russ

Thanks for your observations.  I've towed at temperatures around 100F without bother but that's running in 4th or 5th gear - little involvement of the torque converter which I believe generates considerable heat.  

On hills, in lower gears, the transmission regulalrly gets to +200F which doesn't seem excessive as the redline is around 275F which I didn't quite reach anyway in the situation I outlined.  A longer hill might have caused problems of course....

But perhaps such heavy-work conditions are simply outside the designed performance of the unit.  Every vehicle must has its limits.  Is my 1 ton pick-up close to its limits towing under such conditions we might ask?

I've read the Mountain Guide warnings about long climbs with heavy loads at high daytime temperatures so maybe it's not uncommon that any such vehicles really are at the limit of their performance under such extreme limits?

I'm still keen to hear what cooling fans there are...

[almost13ranch]

I hope you got your problem figured out. Two observations that I have are this, I would check to see if there are any obstructions in front of or in between the radiator and inter cooler. It would be normal for the fan to make different noises depending on the engine speed and air temperature coming through the radiator, it could also cycle on and off depending on the heat load.  Second, when you experience an over heating problem with the transmission, you should place the transmission in neutral instead of park. Some transmissions do not run pumps in park and wouldn't allow the fluid to circulate to cool.

[macmac]

I hope you got your problem figured out. Two observations that I have are this, I would check to see if there are any obstructions in front of or in between the radiator and inter cooler. It would be normal for the fan to make different noises depending on the engine speed and air temperature coming through the radiator, it could also cycle on and off depending on the heat load.  Second, when you experience an over heating problem with the transmission, you should place the transmission in neutral instead of park. Some transmissions do not run pumps in park and wouldn't allow the fluid to circulate to cool.

Well, no, I didn't ever get a proper explanation of the sounds from the very noisy fan or fans - I still can not figure whether there is only the single, massive viscous-coupled unit or whether there are others not readily visible???

I had checked all the fan/radiator system, blown the Sonoran Desert dust out and removed bugs with a brush.  There was nothing to stop air from passing through the radiators.

I did park in neutral, ran the engine at a fast tickover, and the coolant water readily dropped back to its regular operating temperature (as indicated by the gauge)  What didn't happen, though, was for the transmission fluid's temperature to go down - it didn't budge until we had summited and were heading downhill....  Then both coolant gauge nedles returned to their regular operating positions.

It's quite disappointing that no-one had anything much to offer save for a staff member on another forum.  His math explanation indicated that engine power drop-off at high altitude resulted in my GCW being right on the limit for the Duramax engine....

[almost13ranch]

There should be only one cooling fan. The pitch will vary with engine speed (not just ground speed) and the temperature of the incoming air. the fans are very noisy, it's one of the reasons that they have a fan clutch, another is the amount of power used to turn the fan constantly. you also have to take into account how thin the air is at the altitude you were at, less volume to move through the radiator for cooling.

Also in your original post you stated you parked in"P". While this will be in neutral it will not run the pumps in the transmission. By parking in "N" with the parking brake on, will allow the pumps to run and circulate the fluid. The pumps will run in any position other than "P". The fluid will not cool if not circulated.

I hope this helps.

 

[macmac]

There should be only one cooling fan. The pitch will vary with engine speed (not just ground speed) and the temperature of the incoming air. the fans are very noisy, it's one of the reasons that they have a fan clutch, another is the amount of power used to turn the fan constantly. you also have to take into account how thin the air is at the altitude you were at, less volume to move through the radiator for cooling.

Also in your original post you stated you parked in"P". While this will be in neutral it will not run the pumps in the transmission. By parking in "N" with the parking brake on, will allow the pumps to run and circulate the fluid. The pumps will run in any position other than "P". The fluid will not cool if not circulated.

I hope this helps.

thanks!  Of course you're right - I'd forgotten that I hadn't parked in 'N'.  I was on quite a steep slope and selected 'Park' and applied the parking break hard - I didn't want to roll backwards! 

I did not know that the transmission circulating pumps did not operate in 'Park' - that's something I'll know for the future - thanks again.

You're bang on about less-dense air cooling less effectively - hadn't thought of that one either!

So there's only a single fan.  I really couldn't tell as the noise became so intense at times that it sounded like another fan kicking in - I suppose that was a speed boost setting?  The sound changed pitch regularly and often quickly...

I'm more wary of mountains in the summer now although it's not easy to avoid them - they are often in the way!      I'm pleased I was never tempted to buy a heavier trailer.

 Thanks again - your information has helped me understand the situation.

Keith