Overheating on long pulls?

[alaskax]

I just made my annual trip to Alaska from Illinois, and this year I pulled a 15,000 lb load (tractor) behind. Some record temps were in northern Canada and Alaska (90 deg the last 1000+ miles). I think I encountered the worst set of conditions: there are some really long grades in northern BC, it was about 90 deg, the wind was blowing WITH me a little bit, and my truck would overheat before I could make it to the top. I took my bug screen out, which helped a little, but I still would have to pull over on the hill as my temp gauge pegged, leave it idle for a while, the temp would drop to as low as about 210 deg, then take off again, using almost full power to get that load going again! By the time I was up to about 40 mph in 2nd gear, it was time to pull over again! The slower I went, the more it would overheat. I finally figured out that my best bet was to hit the hills at 75-80 mph (yeow!), and keep the egt's at redline (1300 deg), keeping as much power to it as I could. If I could maintain a high speed, then the ram air seemed to keep the engine below redline. If I could not maintain this speed, then I would peg my water temp gauge in no time! Fluid is full, radiator fins not plugged with bugs, and fan SEEMS to be working fine.



Is this normal for the Cummins? I was really asking a lot of my truck on this trip (I weighed the entire set up on a CAT scale, over 22,000 lbs), redlining water temps and egt's for hour after hour, but have other people had this overheating issue, or is something a little bit wrong? Thanks!



John

 

[Gary - K7GLD]

Wonder if your fan clutch is functioning properly? If you were using all the power adders you list, that contributes lots of overheating potential on steep grades heavily loaded...

 

[CumminsPuller]

John, I am a bit confused. If I read this correctly you weighed the truck and trailer with the tractor on it and you weighed in at 22,000 lbs or a bit over? You also stated the tractor alone weighed 15,000 lbs. That means if you subtract the tractor weight you get 7,000 lbs for the truck and trailer. Did I not understand?



I ran into the same problem pulling coming into Flagstaff, AZ (I believe someone told me it is an 8-9% grade). My truck and trailer combined weigh 16,000lbs. The load on the tralier was 16,000lbs as well. 32,000 lbs total. I did not have it as bad as you though. I hit the hill at about 70-72 and by the time I reached the top I was at about 10 mph and the engine temp light just came on as I crested the top of the mountain. Just took my foot off the throttle a bit and started coasting. Temp dropped and everything has been fine. I think if I had better air intake I would have been alright. I had a BHAF on at the time.



Jason

 

[rweis]

I tow mainly in flat florida (13k). In the next couple of years we are gong full timeing. At that time I am going to add mister cooling to the front end.



16 gallon tank and pump from Northern tool $109

Irrigation misters (. 5 gal / hr probably 4 heads) from Home Depot $10

Misc switch, tubing $25



Should keep the radiator temps down regardless of where we tow and what ever the grades how ever long.



You are depending on air flow speed for cooling in a situation where you may not be able to maintain sufficient speed for the cooling air flow. I would think then you have to find another way to get the cooling effect you need. Horton fan that you can lockup by a switch, secondary radiator, misters, etc.



I would of course first make sure that the stock fan system is actually doing its job correctly before looking at addons. Also consider gearing down to get better torque and air flow through the engine.



I would also find othe CTD's configuered like yours that pull loads like yours and find out what they do.



Bob Weis

 

[keimmmo]

Driving style MIGHT be a factor. I have noticed on mine that if I let the trans do the shifting, it tends to run in too high a gear and will overheat both the radiator and the trans very quickly. However, if I downshift and rev the motor with less load on it, I have no problem at all.



Steve

 

[gonzo2]

You might want to take out the intercooler/rad and separate them for a good cleaning.

I ran into a guy up north last week that was encountering similar symptoms. He said that everything looked clean but between the two was caked up with bugs and dirt. Reported that she worked good after.

 

[alaskax]

Thanks for the responses! Just to clarify, my tractor was 12k, trailer was 3k for a 15k load. I pull with my fueling boxes off. Even then, I can still drive the egt's through the roof. I would have thought that shifting down and pulling the load up the hill at a leasurely pace, in 2nd or 3rd, would be OK, but that is much worse: Egt's are down, but engine temps skyrocket very quickly. I have to drive FAST to keep the water temps down! Sounds like my symptoms were not completely unreasonable, and that perhaps I need to check for proper fan clutch operation (any hints how?), and/or radiator bug blocking, even though I usually run with a screen in front.



John Bruss

 

[klenger]

I'm putting money on the fan clutch. I don't know how to test it, other than that it makes alot of noise when it engages.

 

[CumminsPuller]

Couldn't you open the hood, start your truck then shut it off and watch the fan. If it stops within a couple of seconds its good and if it keeps spinning its bad?



Just an idea.



Jason

 

[rweis]

Try to turn the fan with the truck OFF. If there is some resistance then suppose to be ok, no resistance, not ok.



Probably something in the service manual as well.



Bob Weis

 

[klenger]

The fan clutch won't engage until the air temperature is above a certain temp. This would not happen while parked in most cases, unless your truck is parked in the hot sun in Arizona all afternoon.



That's one of the differences between living in the desert and the rest of the normal world. Here, the fan clutch engages when you start your engine cold (?) and then shuts off a few miles down the road when the engine has had a chance to cool down. This is not a joke, BTW.

 

[rweis]

I've been rethinking my mister system.



Since temps are a concern only when I tow the 5er, I am going to use the water tank and the water pump in the 5er and only run a line and a relay wire from the 5er water pump to the truck. The water line for the misters, the relay line for a switch in the cab.



Just thinking out loud,



Bob Weis

 

[RustyJC]

Bob,



With all respect, our industrial engine and compressor customers who have tried to compensate for undersized fin-fan coolers by spraying them with water during high load and/or ambient temperature conditions have learned a couple of lessons:



1. Deionized or distilled water is a must. Otherwise, calcium (lime) deposits on the cooling fins will foul the cooler and reduce cooler efficiency in no time.



2. Ultimately, the combination of mist and ambient dust/dirt fouls the coolers with a muddy mess that sets up almost like stucco when it dries. Cleaning this substance from the cooler coils isn't easy!



We're pulling a 13,500 lb 5th wheel that puts us on the road at 21,180 lbs GCW (21,500 lbs GCWR) and have never had any overheating problems, even on 100+ degF summer days in the Texas Hill Country. If everything is up to par in the cooling system department, based on my experience, I don't know that "crutches" such as misting systems are really necessary.



JMHO.



Rusty

 

[rweis]

RustyJC,



Points certainly to consider.



I have not gone over about 210* in flat florida yet, fan kicked in and brought it back to 190*, but also have not "gone to the mountains" until August. Before the mountains I am going to flush and change the radiator fluid.



You don't see too many threads about overheating that are not clutch or fluid or thermostat related.



Did not think about the crusty buildup or the lime deposits. That fact makes it not a viable option. Don't need to take the front cooling system apart to clean it frequently.



Good points, thanks



Bob Weis

 

[Mingoglia]

I have an '01 and live in Phoenix (have a 3500 5sp dually 4X4 3. 55). I pull just under 20k lbs according to the Cat scale. I can run up several mile long 7% grades at redline and only get the gauge half way in the middle (by middle I mean in the middle of normal temp and hot... so I guess that would be 3/4 on the gauge). If I bring engine speed under about 3000 it cools off considerably. In fact, bringing engine RPM "in check" brings me just above normal. This is in 105 degree weather. I'm going to my favorite camping spot again this weekend with the same trailer (will be about 750lbs lighter). This weekend I'm sure the temperatures will be closer to 110 as it's warming up. I'm sure I won't have any problems. Engine temperature just has never been an issue for me in Phoenix.



Just a side note, my engine EGT with my Edge EZ is a solid 300-350 degrees lower than stock. My temperature probe is POST turbo so keep this in mind. When stock, I had no problem pulling my trailer and hitting 1050 degrees (post turbo) even in the winter time pulling agrade... . and ultimately having to back off the throttle. The highest I have EVER seen is 875 degrees post turbo regardless of temperature or load.



Mike

 

[John Berger]

I've pulled my 5'ver in some pretty warm weather in Florida, Georgia and the Carolinas and Tennessee. The warmest I have ever seen my engine temp while towing is right around 200 degrees and it did not stay there long. I run the Cummins pre-mix in my truck and change it every other October regardles of mileage, high or low. The highest temp I ever saw on my truck was when Cummins in Jacksonville dyno'd it for me. It crawled up to about 220-225, but there was no airflow.



My 5'ver weighs out at 12. 4K, so I'm not pulling quite as heavy a load as you guys are talking about, but I'm surprised at your problems nonetheless. I tend to agree with the points made about a properly functioning cooling system and the driver's technique.



Something to think about.

 

[I-6DZL]

Guys, before completely condeming the Cooling Fan, or the Thermostat, or even the Coolant, remember one thing the radiator cap. If your cooling system doesn't have proper pressure on it (15 lbs i think) the system will over heat. for 1 lb of pressure the temp will decrease 7 degrees (if remember right)



curtis

 

[rweis]

I went to Cummins and bought fresh 50/50 mix and a thermostat. I decided that it will be a every 2 year change thing just like changing oil.



About the same $$ as the "band aid" was too.



Y'all convenced me, y'all are right,



Bob Weis



The local Discount Auto will not take antifreeze because it screwes up their waste oil. What do you do with it to dispose of it properly?

 

[Berrigan]

Alaskax



My experiences are the same as yours. Hard pulls at 22k gcw in 100 degree plus ambient temps. If the truck will pull the grade in 5th, my egts and coolant temps get to high. If I downshift to forth both come down. But on long steep grades in fourth I can ring the overheat bell.

 

[RustyJC]

Which, going back to my earlier post, raises the question about BOMBed trucks. The factory engineers sized the cooling system for stock ratings and associated heat rejection rates at a set of defined ambient conditions, plus some margin (usually 10% in our industry). As soon as we BOMB our trucks and then try to pull 7% grades on 100+ degF days at or above GCWR, the cooling system is, by definition, probably undersized. At that point, all bets are off regarding the ability of a stock cooling sytem to keep coolant temperature within acceptable ranges.



Rusty