I have been researching Duramax over heating issues. I have been having trouble with my 07 overheating. In my case I pull a boat (2400 lbs) often on mountain roads. Outside temps range in the low to mid 70s. When pulling the hills the temp begins to climb and continues to rise, it does not cool off until I am heading down hill, or pull over to stop. I have read some posts that describe the fan coming on and the engine cooling off. I have never had this happen. I plan to begin hauling my camper as well this week, and I am worried that the the Duramax will not do the job.

Any suggestions:

Also, I have noticed that the upper radiator hose seems to be partially collapsed. Is this normal

Comments and suggestions are appreciated.

Thanks, JCC

Not normal to collapse a hose. Suspect a bad 'radiator cap' on the coolant bottle not releasing the vacuum. With the cap off if the hose is still collapsed replace it. Check other hoses as well for collapse or kinks esp. to the clear coolant bottle.

Check the condenser for bug build up. Screens are a restriction.

Fan clutch should also be checked for proper operation. Under warranty?

Shift out of 6th before the hill and keep the RPM up for the fan and water pump when towing. The factory shifting will lug the $hit out of the engine without enough RPM for the fan and water pump to work well and cheerfully let the temps rise. 235+ ect out of the computer towing heavy appears to be normal even with dowshifting.

Have you checked the air filter for restriction? Plugged K&N (junk) filter and/or intake equipped? Gauge on intake is worthless and will suck the filter out before showing anything... A restricted turbo is a great air heater. Hot Charge Air Cooler in front of the radiator and well the radiator can't cool anything.

Some tunes out there, reference my signature, that reduce boost like a old waste gate would and cut down the heat load on the cooling system. Specific for towing. Track use is a different tune...

I have been researching Duramax over heating issues. I have been having trouble with my 07 overheating. In my case I pull a boat (2400 lbs) often on mountain roads. Outside temps range in the low to mid 70s. When pulling the hills the temp begins to climb and continues to rise, it does not cool off until I am heading down hill, or pull over to stop. I have read some posts that describe the fan coming on and the engine cooling off. I have never had this happen. I plan to begin hauling my camper as well this week, and I am worried that the the Duramax will not do the job.

Any suggestions:

Also, I have noticed that the upper radiator hose seems to be partially collapsed. Is this normal

Comments and suggestions are appreciated.

Thanks, JCC

Define overheating and with a 2400 lb boat then I doubt your sitting on the side of the road spewing coolant. If your temp begins to rise then the fan should come on period. You have to be at 230 before you worry and by then the fan should be screaming and cooling you back down. Pulling it out of 6th is a good idea but I think you have problems if your fan isn't coming on and I don't see how a 2400 lb boat gets it that hot. I'm pretty confused about this whole affair unless you have the thing floored trying to go up that hill and well then I would expect you to heat it.

Define overheating and with a 2400 lb boat then I doubt your sitting on the side of the road spewing coolant. If your temp begins to rise then the fan should come on period. You have to be at 230 before you worry and by then the fan should be screaming and cooling you back down. Pulling it out of 6th is a good idea but I think you have problems if your fan isn't coming on and I don't see how a 2400 lb boat gets it that hot. I'm pretty confused about this whole affair unless you have the thing floored trying to go up that hill and well then I would expect you to heat it.

Not spewing coolant. However the warning light comes on and the dash board gage starts hitting 260.

I agree 2400 pounds should be a breeze. My previous rigs never had any such temp challanges. This is why I am looking for some friendly advise.

Uphill speeds yesteday ranged between 20 and 35 MPH (2nd, 3rd, and 4th gear).

The fan never cooled the unit down.

I will replace the cap and upper hose, load the camper and take another chance on Friday

I think you have a fan problem. I just pulled a 12,000 pound 5th wheel through the mountains with some hills at 8% grade. 102 degrees outside. Doing 60mph with tow/haul switch on, engine temps only got to 235 degrees. Transmission temps got to 223 degrees.

You should hear the fan coming on. It should sound like a jet engine going off if you have engine temperatures of 260 degrees. If you are not hearing this, I would suspect the fan.

I think you have a fan problem. I just pulled a 12,000 pound 5th wheel through the mountains with some hills at 8% grade. 102 degrees outside. Doing 60mph with tow/haul switch on, engine temps only got to 235 degrees. Transmission temps got to 223 degrees.

You should hear the fan coming on. It should sound like a jet engine going off if you have engine temperatures of 260 degrees. If you are not hearing this, I would suspect the fan.

Thanks, I will check the fan out as well!

You shouldn't even have to run tow haul but try it anyways as it will still keep the trans cooler and lowering anything up front in that big heat sink helps. Swear you must have no fan at all or even bigger problems.

definately look into the above coolant suggestions.

Do use Tow Haul. As mentioned, shift into Manual5 or lower if not going highway speeds to help with both engine and trans cooling and keep RPM's up.
Most people that are posting with a 2400# boat are quoting the dry boat weight, add trailer, fuel, gear in boat, you are looking at 4,000+
These trucks are powerful but no replacement to smart driving.

I have been researching Duramax over heating issues. I have been having trouble with my 07 overheating. In my case I pull a boat (2400 lbs) often on mountain roads. Outside temps range in the low to mid 70s.


Not normal at all. I pulled my 8K trailer 500 miles in Florida running 75 with the outside temp 95. Truck never went over 210. Granted Florida is flat, but still.


Also, I have noticed that the upper radiator hose seems to be partially collapsed. Is this normal


Happened to me too. I soaked my radiator cap in warm soapy water for a few hours and cleaned it really well and now no more collapsed hose.

Not normal at all. I pulled my 8K trailer 500 miles in Florida running 75 with the outside temp 95. Truck never went over 210. Granted Florida is flat, but still.



Happened to me too. I soaked my radiator cap in warm soapy water for a few hours and cleaned it really well and now no more collapsed hose.

Thanks for all of the advise. I head back to the same lake tomorrow, changed the cap and replaced the hose (all I had time for this week). I hope to have better results.