Pre emission DDEC IV D60 12.7 Coolant Temp Issue

[leggs972]

Purchased a 2016 Fitzgerald Glider Coronado in March '18, used, with 310k miles. 1998 12.7l motor, few parts & their tune to take it to 500 hp. Beautiful truck, runs great.

After running it for about 6 weeks, one day threw a coolant temp code. Stopped, checked out the engine & everything seemed OK, coolant level good, didn't seem excessively hot. Since that day, periodically it throws the code. One day I stopped for my 10 hr break, woke up, started the truck, & after letting it warm (outside temp was maybe 75 degrees) for a few minutes took off. A block down the road it threw the coolant temp code & I wasn't up to 30 mph. This particular incident made me think "sensor". Replaced that. No joy. Replaced the thermostats for peace of mind, no joy. Called Fitzgerald & one of their techs said it sounded like the impeller may be spinning on the water pump shaft, or that the engine harness may be bad.

So... took Memorial day off and spent 4 hrs of it replacing the engine harness. Won't be going out for a load until tomorrow so we'll see if that corrected the problem.

Any thoughts? Radiator & CAC look good. I can pull serious grades & temp stays at 175. Other times I can be on level to rolling & the buzzers will be sounding. The gauge will go from 175 to 225 or 250 instantly, stay there for a second or two, then shoot down to 125 or 150 just as quickly.

I'm really hoping the harness was the problem, but we'll see. Seems like if it was the wp impeller it would be a constant issue.

Appreciate any feedback.

[imalumberjack]

I would guess wiring also, if you got up to 250 you would know it and shooting back down to 150? yeah I'd say your heading in the right direction. A twenty dollar laser temp gauge might confirm.

[pearce trucking]

Maybe a loose connection in the coolant temp sensor plug? It would seem to be an electrical issue with your description. Obviously coolant temperature doesn't change that rapidly.

[leggs972]

(05-28-2018 )imalumberjack Wrote:  I would guess wiring also, if you got up to 250 you would know it and shooting back down to 150? yeah I'd say your heading in the right direction. A twenty dollar laser temp gauge might confirm.

Engine harness did the trick