Is it normal for the CTD engine to heat up quickly when down shifting to reduce the exhaust temperature? I had to slow down because of the water temperature. The temperature was at its upper limit. I was the same speed as the truckers. At one point all I could do is 22 mph.

My truck and trailer weighs 20,800 pounds. The road where this happens is HWY 80 from past Auburn, Ca to Truckee, Ca. 6% grade 45 miles long.

What can I do to keep the engine cooler? It is basically a stock HO truck with a 6 speed manual transmission.

 

First thing to do, and this is a must, go to Cummins and get a new 180 degree thermostat. They are a problem and if it is the OEM thermostat it is normally not too good. Mine never goes over the center line.

 

Did you ever hear the fan clutch engage? When towing our 16,000 lb GVWR 5th wheel, about the only time the fan clutch engages is on a long pull up a good grade. When it does, coolant temperature drops like a rock. I've never seen coolant temps over about 195-200 degF when towing, even in 105 degF Texas summers. And that's with the original 190 degF thermostat.

Rusty

 

Flush your radiator from the backside with a water hose. Mine had a lot of crude in there that was not being cleared by flushing from the front.

 

There is a TSB that applies to 01's for a Tstat change that goes to a cooler one. Making sure the fan clutch works is good advice, and look down in front of your radiator. If there is a circle of crud where the fan is you need to remove your radiator and have it cleaned. We find the nice design of the "puke bottle" being mounted in the fan wash will coat the fan and radiator with a fine mist of oil. Of course dirt sticks to this and after years of repeating this, the fins clog and reduce cooling. I've removed three radiators this spring for this....also relocate your bottle, or rid of it and extend the hose below the level of the fan. See my picts to see where I put my bottle.

 

Thank you for the ideas. I have each time hosed out the radiator before I haul. I'll have to check the fan. A T-stat change will be done.

What gets me is how fast the temperature rises. I'm at the upper limit within a mile to two on a grade.

 

If you're not sure, then the fan clutch probably isn't working. When it kicks in, it sounds like a 747 is taking off under the hood!

Rusty

 

How often will the fan engage? I believe I only hear it engage while on a long (30 mile) slight grade in the middle of Nevada.

 

On mine, it engages when coolant temps reach about 200 degF or so. It's a thermal clutch, so it depends on the temperature of the air passing over it. If you're reaching the end of the operating band on the coolant temperature gauge and it doesn't engage, the clutch is probably defective.

A sticking thermostat or a dirt-fouled radiator can also affect fan clutch operation. If the thermostat is stuck closed, the coolant temperature in the radiator will not get hot enough to engage the fan clutch. If the radiator is severly dirt-fouled, not enough airflow will come through and/or heat transfer take place to the cooling air to engage the fan clutch.

Rusty

 

Is this the same with 3rd gens? I was towing 6500lbs in traffic and I seen the temps go past 200, so I turned the heater on and put the windows down and it gradually came down. Didnt hear any 727 take off under my hood.

 

I believe the 3rd gen engine fan is controlled by the PCM.

Rusty

 

The 3rd Gens make the same noise! But they are electronicly activated. You will hear it engage. You may have to go above 200 deg for this to happen. It will engage more often with the air cond. on also!

 

More than likely the Tstat is either plugged or not opening all the way.

 

One of the first tips that I was given on this board when I joined was the thermostat. I was told to change it because the OEM was not good for towing. I used to have to back out of it on hills towing, changed it and have never backed out since. They comprimised towing temperature for faster warmup.

 

couple weeks ago i was heading up a pretty steep backroad hill doing about 25-30 mph with roughly 10,000 lbs and temps got past the 200* mark and my fan egaged and defueled my truck, put the AC on full blast and temps came right down real quick while still climbing... i heard somewhere turning on the AC helps cool it and after i tried it, it seemed to work awesome.