JimDeville

1997 Deville Overheating Leaking Pressure Tank

7 posts in this topic

    Hi Folks, My name is Jim, I'm happy to be a new member of the Caddy lovers club! I'm 54, been a caddy lover since my teens when my dad got his 4th or 5th caddy. In my 20s He came across a beautiful late 60s red convertible with a white leather interior which he slapped some plates on & let me take her for a ride to have my tooth pulled. He neglected/forgot to tell me the brakes were non existent brakes (master cylinder) so I used the emergency brake, made it to the dentist & home! Ever since that & my dad's subsequent Cadillacs I've been hooked on em. I've had 3 or 4 Devilles & I currently own a 97 I've had for 3 years. It has 214,000 miles on it. It was not well maintained, unfortunately. Most Cadillacs are big, solid built cars that have great comfort, quality motors & I feel safe having my wife drive one with our kids in the car.

That was a funny post about trading the Caddy in for a Daewoo!  I have a 2002 Nubiro that's a piece of, you know. That topic post was from 2004 I think. Anyways here's my situation. My 97 Deville 4.6 Nothstar Y is bubbling over 251-260 degrees. I have leaks in the pressure tank & have ordered a new one. My question to you experts out there is the leaking tank enough to cause overheating due to loss of pressure? I am not a mechanic though I can remove & replace  parts, swap motors, etc. but I'm not a cooling system guru! I am concerned it may be a head gasket issue. I checked the exauste pipe, no moisture. Oil & coolant are clean, purge pipe open, water pump ok(replaced last year & removed cover to check), new stat, good hoses. I have not been able to perform a pressure test not have I checked for combustion gases yet.

I think it's the pressure tank leak (at the filler neck & at the purge hose) causing overheating & certainly loss of coolant? Can you guys help me out please? Thank you!!

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:welcomesmiley: Welcome, Jim.  

 

The cooling system does depend on the mixture of water to antifreeze and for pressure to raise the boiling point of the coolant.  Our primary question though is whether you are having exhaust gases escape into the coolant and that us causing overheating.  You can get a test kit from the autoparts store to test the coolant for exhaust gases.  Also there are other things to check.  Are you getting any diagnostic trouble codes?  Are the engine cooling fans working in both speeds?  Any other recent changes or maintenance?


Bruce

2016 Cadillac ATS-V gray/black; 2013 Cadillac ATS 2L Turbo Premium (Wife's)

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Hi Bruce, thanks for the welcome. Haven't pulled codes, but I will and I'll check out the exhaust gases  test kit tomorrow. The cooling fan relay was blown, replaced it & fans are fine. Motor runs great. No white smoke, no excess moisture in exhaust, plugs DO get black rather quickly like 1200 miles, I think because it burns some oil. It will hold at 251F in idle on hot day in Florida without thermostat. But if I drive around town it goes 260F & I shut it down. I guess best next test is should be for gases in coolant? Then after new tank arrives pressure test the system? 

Thanks again Bruce for your help I really appreciate it!!

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Fans were out but working right now? The cooling system is a balance of coolant mix, pressure, fans, and system integrity (incl head gaskets/bolts).  So to diagnose each one has to be examined.


Bruce

2016 Cadillac ATS-V gray/black; 2013 Cadillac ATS 2L Turbo Premium (Wife's)

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JD - I think you are referring to the surge tank, is it leaking or is coolant coming out of the overflow hose? It could be something as simple as the pressure cap not holding pressure or if the surge tank itself has a leak that will cause the same effect because the system will be unable to maintain 16psi. 

Bruce Nunnally likes this

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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Hi Guys, Thanks Bruce you're right it's a balanced system, need to check each part. Yes, the cooling fans were out for about an hour, got the new relay & they're ok now. The surge tank has actual cracks in the plastic that are leaking steam, pressure, coolant. Definitely not holding pressure. That's why I was wondering if no pressure alone like leaving the pressure cap off & driving around in hot weather would cause overheating by itself. 

  Thanks JD, yes, coolant leaking from overflow hose & tank. Tank has bad leak at both hose connects, plastic has failed. Going to test the system today for the head gasket leaking, hopefully it's not. The new tank comes next Monday, after that I will put in tank & new cap & pressure test to hold 16LBS is that correct? Just trying to keep her running good til I can get a newer one. Need it to be dependable for wife & kids. Wish I had joined this forum years ago! 

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Water boils at 212F.  A water-antifreeze mix boils at sea level at around 225F (Dex-Cool at around 228F).  However, raise the pressure and the boiling point goes up, as a thumb rule about 3F degrees per pound of pressure.  So a proper 50/50 mix of coolant under 12 psi of pressure should not boil until 225F + 3F/psi  x 12 psi = 261F+.  Once the coolant boils it becomes worse at heat transfer to the radiator, and at staying in the system.  So yes, keeping the system pressurized is key for proper operation.

 


Bruce

2016 Cadillac ATS-V gray/black; 2013 Cadillac ATS 2L Turbo Premium (Wife's)

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