Why is my Deville overheating?

Asked by knappclan Mar 14, 2020 at 07:31 PM about the 2005 Cadillac DeVille

Question type: Maintenance & Repair

05 deville overheating. Compression checks good
at 138 to 150. Changed thermostat. Purge line
seems ok with a steady trickle of coolant back to
the reservoir. Both fans are running. Heater blows
out hot air until temperature indicator goes one or
two bars to the hot side and something happens
and starts blowing cold. I'm completely stymied.
Any help would be much appreciated.

2 Answers


Sure sounds like blown head gaskets, you can get a test kit from your local parts store and DIY it or have a shop run the test.

1 people found this helpful.

Absolutely, the Northstar Engine is notorious for blowing head gaskets. They all blow head gaskets sooner or later! The cylinders showing the 138 PSI compression are suspect. That's on the low side! The only way to do the head gaskets on this vehicle is to remove the engine and transmission from the bottom of the vehicle. There's no other way! Get the test kit to confirm this! Hope that helps! Jim

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