3.0 Duramax engine temp erratic going all the way up to redline 260 degrees, heater blowing cold air

Bikerjon · April 27

4 hours ago, Cleveland Francois said:

I'm experiencing something similar with my 2020 AT4 with 139k miles. Never had any issues before.

Check the coolant level in the radiator (not the overflow tank).

Wayne Black · April 28

This happened to me once in a '67 Corvette back in early '70s. The temp would start to rise up to redline and then I would go around a corner and it would come back down.

Turns out there was an air bubble in the system.

When the car was cold you could check the radiator and everything looked fine. It was full.

When the engine was hot I loosened one of the heater hoses enough to let the steam out (dangerous by the way) and after it was done I removed the radiator cap and poured in over a gallon of water.

The car was fine after that.

3.0 Elevation · October 16

I have a 22' Sierra with the 3.0 Duramax and 73k miles. Over the past few months, the temperature has spuratically elevated to a point that the a/c would shut down and the go into a reduced power mode. Come to find out, the intercoolers are defective which allows coolant to mist and leak into the turbo. Needless to say, I had to replace both the intercooler and turbo.

Knowing that dealer service departments are pretty busy and I would have had to drop my truck off, pay for a rental and in the end them tell me it's not covered under warranty- I went to a diesel expert who is very knowledgeable in these motors.

The good news is that the 3.0's are great motors..the bad news is that they have a series of failures that need to be "bulletproofed". I'm sharing this information so that it may help someone else. I recommend installing an upgraded aftermarket intercooler which has a manual drain.

As for GM, it's pretty sad that this has happened..the quality of American made cars/trucks isn't what it use to be.