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2003 Deville - cooling system problems

3848 Views 34 Replies 5 Participants Last post by  20grand
I have to do this on my Deville in the AM. It drives and rides nice but after a while at idle the gauge will increase and cold air kicks through the vents. After I rev the rpms real high, the gauge comes back down and then I have heat. I also checked the tank and she's nice and full. Was thinking maybe a faulty thermostat but will check the lines before I pull that out.
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Re: Overheating - 2002 Eldorado

A faulty thermostat won't cause the heater to blow cold. That's caused by air in the cooling system getting into the heater core.

Here are the two ends of the purge line.


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You either STILL have air in the system, or ARE PUTTING air in the system.
Do the block test again as soon as possible after the overheat episode. Sure sounds like you are putting exhaust gases in the cooling system. Probably in the early stages.
Amazing what something as simple as a surge tank cap can put you through. It's always the last thing you think of and check. Good luck and keep us posted. Inquiring minds want to know.
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