The Cummins tech told me that the oil thermostats were 239 degrees so 230 is about right.

Oil was tested and showed chemicals consistent with coolant. When the oil changer poked holes in the oil filter some green fluid came out before the oil.

When I took it to Cummins they said troubleshooting the problem took several steps. I was fully aware that changing the thermostats may not fix the problem. I am not making much money at this yet so I am careful not to spend more than I have to. I guess I havent spent enough yet.

 

Sounds like a oil cooler is in your future.

Take your water filter off and see if it is full of oil. If your oil cooler has a hole in it your water filter will catch the oil.

Mine had a double oil cooler on it so it was a little more expensive to replace. I think it was around $2000-2300 to replace.

 

Ever since the first Cummins Turbo Charged 270HP, 855CI engines, the engine oil has been used to cool the pistons from the bottom. That's why oil temp is usually a little higher then the coolant temp. The pistons get very hot under a load so it would not be uncommon for the oil temp to get a little high when your pulling a long grade but the ECM should cut the power back before the oil temp light comes on.

Do you have a pyrometer (exhaust temp gauge) and have you noticed where its running when the oil temp light comes on?

If you are getting oil in the coolant and/or coolant in the oil, there are a few things that can cause that. The oil cooler has been mentioned and would be the most common failure. A pressure test by Cummins should help find the problem without all of the guess work.

 

So we all went the same place. Since my indication was oil overtemp we all fixated on oil. The problem was, are you ready?

Water temp sensor reading too low!

To exacerbate the problem my fan clutch hub was bad and I had a small hole in my heater core bleeding off pressure.

At any rate, I took it to Volvo in Albuquerque and said, fix it. I ask him how it was possible to boil coolant at 170 degrees. We replaced all the broken stuff and tested it. Still funky readings. Changed the temp sensor and everything fell in. Water temp was reading 130 to 150. Changed the sensor and water temp jumped up to 180 to 200.

Climes the hill on i40 and the oil never budged above 231.

 

Thanks for the update LostSoul.

So it would seem that the temp sensor was the key component here. It was not reporting the correct temp to the computer so the engine was not cutting back as the temp climbed. The only indication was in the oil temp. I hadn't heard that the coolant was boiling.

I wonder if the fan hub was really bad or just not coming on because of the incorrect coolant temp reading.

Were you having any issue with fog on the inside of the windows from the leak in the heater core?

 

Shnerdly, you hadn't heard that the water was boiling because I forgot to mention it. That was the missing piece. While stuck on the side of the road near flagstaff waiting for her to cool it hit me...water doesn't boil at 170 degrees and if the temp sensor was defective and the coolant was much hotter than what was being reported all of our current symtoms would occur. And of course with the heater core leaking blessing off pressure it made it even worse.

Actually it wasn't the fan clutch but the hub that was bad.

 

Hi,

for charge air cooler queries of problems you should contact Vestas aircoil, they manufacture and design charge air coolers for large diesel engines. Not so much for trucks though, but should be able to give any advise regarding cooling.

 

Hi,

Reading through the posts here on charge air coolers, if you have any questions I may be able to assist. I work for a company called Vestas aircoil who design and manufacture charge air coolers for diesel engines.