Deville pressure build up in coolant system. - Page 2
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, Deville pressure build up in coolant system. in Past Cadillac Vehicle Discussion; That was a close one. Glad we where able to save you some money. A clogged purge line will give ...
  1. #16
    Ranger's Avatar
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    Re: Deville pressure build up in coolant system.

    That was a close one. Glad we where able to save you some money. A clogged purge line will give the symptoms of a failed HG. Now, DO NOT use any more of those damned sealant tabs (I know they are recommended in your owners manual, but GM realized this problem as well and quit using them around 2002). Hopefully you got a good deal on this pristine car with a "potential" HG problem. Previous owner is gonna kick himself if he finds out what a simple repair it turned out to be.

  2. #17
    2008DTS is offline Cadillac Owners Member
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    Re: Deville pressure build up in coolant system.

    Hi,
    Just jumping in late. I also have a 2002 Devile Base 130,000 miles. kept filling because coolant low message kept appearing. Turned out being a bad float in the tank (changed later)
    Tried the CO coolant test with the engine just warm. Tank was almost full (overfilled as I found out), and had a little steam coming out the of the tank, but the antifreeze was just warm. After several times pumping air into the fluid it changed colors slightly (to positive).I read your thread and had fluid flowing from the crossover hose ok.
    Never really noticed any excess pressure in the coolant tank when removing warm or cold until I changed the overflow tank and the cap. Now there seems to be pressure when I remove the cap? It is the old style notched cap. First turn 45 degrees (supposed to release pressure I thought) then push down and turn another 45 degrees. When I got to the second notch, the new cap had quite some pressure. The car had been driven several hours earlier and slightly warm. this never happened with the old cap. So i am re-using the old cap. does anyone think it will cause any harm?
    When checked warm with the old cap there is not any excess pressure. Coolant level does not change with either cap. I guess I am of the thinking if the car does not overheat, why increase the pressure in the system.The only difference I have noticed is a slight coolant odor when the car is hot after shutting down with the old cap. When I use the new cap there is no coolant odor.
    I also changed the coolant with the tank replacement (After the CO test) and it looked new. I followed the thread for the drain and refill procedure. I was able to get about (2) gallons out by slightly pressurizing the tank with air using a shop rag around the opening yielded at least 3/4 of a gallon out the radiator drain
    All comments are welcome.

    Thank you everyone
    Quote Originally Posted by mrqvellie View Post
    yes i did. and it does. i bought it from a guy with possible head problem otherwise in pristine condition. but it drove way too long without overheating and when and you had to rev the motor to get heat. he had it full all the way to the top. i replaced the freespining water pump. and put it back like it was. wow never really thought about the fact that anitfreeze expands. i was about to rip it apart til i found yall page and seen the purge thing and decided to post. thanks guys (Ranger)i was literally minutes from ordering a 500 buck stud kit.

  3. #18
    MoistCabbage's Avatar
    MoistCabbage is online now Cadillac Owners 10000+ Posts
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    It's a pressurized system, there's SUPPOSED TO BE pressure built up when the system is hot or warm. Put the new cap back on.

  4. #19
    Mr.electric is offline Cadillac Owners Member
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    The master tech at my shop tests cars for hg failure as follows:
    -Warm up the car
    - put in one of those funnels that has a radiator cap at the base. Fill the funnel with coolant
    - rev the motor and look for a constant stream of bubbles. The more bigger bubbles the larger the failure.

    Keep in mind even non failed cars produce some minor bubbles. It is a matter of how many bubbles and how large the air bubble are. Constant champagne glass bubbles is bad. Burbling jakuzi boiling bubbles is really bad.
    I personally use a block tester with the blue fluid.
    To each his own.

  5. #20
    2008DTS is offline Cadillac Owners Member
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    Re: Deville pressure build up in coolant system.

    Thanks to both of you for your very quick responses! I am very grateful.
    I suppose I should use the block tester with the blue fluid again. As I mentioned the tank was over filled. There were not any bubbles in the tank. My mechanic kept pumping air into the blue fluid while accelerating the engine, afer about 2-4 times it started to turn colors,slightly yellow I think.
    I guess you answered my question that all cars could have some exhaust gas in the coolant.
    The car has been great (Knock on wood!) Driving in temperatures that range from -10 F to 108 F, the temperature gauge stays in the same place right in the middle of the digital gauge! It has always been there in the 100,000 miles I have driven the car. There has been no collant usaage. There is always good heat and A/C.
    I forgot to mention that when I changed the tank, it was the first time I changed the antifreeze. the inside of the overflow tank was very clean. I had to fill with hot water and shake just to get a slight film (Like inside an old water tank) to come out. (I thought the float was stuck in the sludge/GM Pellet residue)
    Hopefully it will last another 100,000 miles, just love the car!

    Thanks again everyone!

  6. #21
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    Quote Originally Posted by 2008DTS
    I guess you answered my question that all cars could have some exhaust gas in the coolant.
    WRONG. ANY amount of combustion gasses in the cooling system indicate an HG failure.

    If the fluid changed color AT ALL, there are combustion gasses in the cooling system.

  7. #22
    basscatt's Avatar
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    Re: Deville pressure build up in coolant system.

    Quote Originally Posted by MoistCabbage View Post
    WRONG. ANY amount of combustion gasses in the cooling system indicate an HG failure.

    If the fluid changed color AT ALL, there are combustion gasses in the cooling system.
    ----------------------------

    100% CORRECT -

    the ONLY way to get ANY exhaust gas into the cooling system of a Northstar motor -
    is through a failed head gasket - PERIOD -

    you will never "see bubbles" in the serge tank - of a Northstar powered car -

    the PURGE LINE is what allows the trapped air/gasses out of the cooling system -
    and the PURGE LINE is above the normal fluid level -

    the PURGE LINE is unique to Northstar motor

  8. #23
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    Re: Deville pressure build up in coolant system.

    Thank for making that clear.
    Time for another coolant test.
    Is there a preferred method or shop the does the work that will last in the northeast. I live in southwestern PA and would not mind traveling to get it done correctly.
    Thanks,

  9. #24
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    Re: Deville pressure build up in coolant system.

    Quote Originally Posted by 2008DTS View Post
    Thank for making that clear.
    Time for another coolant test.
    Is there a preferred method
    Yes, do it right after an overheat episode and DO NOT add coolant before hand.

  10. #25
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    Re: Deville pressure build up in coolant system.

    Coolant pressure builds up because it heats up and expands. That should be the only source of the pressure.

  11. #26
    2008DTS is offline Cadillac Owners Member
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    Re: Deville pressure build up in coolant system.

    Hi, Ranger,
    I will try the coolant test again. The car has NEVER overheated. I understand that you can borrow one at AutoZone (just purchase the test fluid)

    Thanks

    Quote Originally Posted by Ranger View Post
    Yes, do it right after an overheat episode and DO NOT add coolant before hand.

  12. #27
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    Re: Deville pressure build up in coolant system.

    [QUOTE basscatt] the PURGE LINE is unique to Northstar motor[QUOTE]

    Not quite
    - my two F-150's, with separate coolant reservoirs and 18 psi caps, have purge lines that operate the same way as the Northstar setup. I would imagine that the system holds true for many vehicles with divorced reservoirs.

    Here's the 2004 4.6 4X4 setup. The "FULL COLD" legend is the funny looking black blob on the front side of the "degas bottle" (???).

  13. #28
    Mr.electric is offline Cadillac Owners Member
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    On my northstar I notice the coolant level pulls down significantly in the reservoir when I apply throttle , car stationary. Then when I release the throttle the coolant level comes back up. I would guess this is the aging hoses swelling as water pump creates pressure under increased rpms. One of the keys to properly diagnosing any model is having a mental map of what is normal for that model. You can get in trouble applying experience from one make and model to a totally different make and model. That being said I have always felt the opening the cap on a cold, parked car and finding pressure is a sure sign of head gasket issue.

  14. #29
    2008DTS is offline Cadillac Owners Member
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    Re: Deville pressure build up in coolant system.

    Hi, I checked, car was cold with a new cap and bottle. Opened and there was not any pressure. I guess it was too warm the last time I checked the coolant tank for pressure.
    Thanks,

    QUOTE=Mr.electric;3306098]On my northstar I notice the coolant level pulls down significantly in the reservoir when I apply throttle , car stationary. Then when I release the throttle the coolant level comes back up. I would guess this is the aging hoses swelling as water pump creates pressure under increased rpms. One of the keys to properly diagnosing any model is having a mental map of what is normal for that model. You can get in trouble applying experience from one make and model to a totally different make and model. That being said I have always felt the opening the cap on a cold, parked car and finding pressure is a sure sign of head gasket issue.[/QUOTE]

  15. #30
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    Re: Deville pressure build up in coolant system.

    Quote Originally Posted by Mr.electric View Post
    On my northstar I notice the coolant level pulls down significantly in the reservoir when I apply throttle , car stationary. Then when I release the throttle the coolant level comes back up. I would guess this is the aging hoses swelling as water pump creates pressure under increased rpms.
    It's normal and not aging hoses. As the RPM's are increased, so is the WP RPM and that is simply sucking coolant out of the surge tank to supply the increasing WP "demand", hence the name "surge" tank.

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