View Full Version : 2001 Deville - coolant boiling in reservoir

04-21-14, 08:50 AM
Hey everyone I have a 2001 deville DTS and I have changed water pump, did a combustion leak test with a negative result. And I have water boiling in reservoir but engine doesn't get hott? Is this a pressure issue? Any help with this is greatly appreciated

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04-21-14, 10:28 AM
First, study the sticky threads just above this - cooling system, fans, and gauges - for insight and information, then begin careful diagnosis.

There is also cooling system info way up ^^^ in the top black bar - the Cadillac Technical Archive. Info you NEED to know.

Your system cap is set for 18 psi and that's about what pressure the system should run at. Take a look at what pressure does to boiling point of various coolant mixtures. Note the bottom line is the recommended 50/50 mix. GM allows you to go to 70/30 in extreme temperatures.

04-21-14, 10:33 AM

This is contradictory. If you are in fact boiling, the engine has to be hot. If it is false boiling (air bubbles in the system) the block test should be positive because you are pumping exhaust gases into the system to cause the air bubbles. Is your surge tank cap holding pressure? Is your purge line clear?

04-23-14, 06:13 AM
To me it sounds like your cap isn't doing the work.

04-25-14, 11:06 AM
on the expansion tank, where the cap screws on its a metal piece formed into the plastic, if your cap is good run your car almost to operating temp and spray soapy water at that seam, could be relieving pressure there, my 01 DTS did this to me.