Engine overheating problem
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, Engine overheating problem in Past Cadillac Vehicle Discussion; 2000 DHS: While on the interstate, the alarm sounded indicating my engine was overheating. I pulled off to the side ...
  1. #1
    DaleCad is offline Cadillac Owners Member
    Automobile(s): 1979 Coupe DeVille, and 2000 DHS
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    Engine overheating problem

    2000 DHS: While on the interstate, the alarm sounded indicating my engine was overheating.
    I pulled off to the side and let it cool down. When I checked the coolant level, it was empty!
    It was full when I left home. A family member came to my rescue with more coolant, and I was
    able to complete the remaining 50 miles of the trip without overheating. He suggested I should
    have a complete cooling system flush and a new radiator cap. This I did. Recently I made
    another trip and the same thing happened: engine overheating and coolant nearly empty.
    I was flabbergasted after having a total system flush and new radiator cap. Fortunately,
    I carried more coolant in my trunk and filled the radiator. Once again, I completed my trip
    without incident. I'm stumped! Why does this engine keep overheating even after new
    coolant and a new radiator cap??? I'm afraid to take it on the highway again for fear
    of repeated overheating. I welcome any ideas for getting to the root of the problem and
    solving it!


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  3. #2
    MoistCabbage's Avatar
    MoistCabbage is offline Cadillac Owners 10000+ Posts
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    It's overheating because it's loosing coolant. There's a leak, and a coolant change and new cap isn't going to fix it.

    The first thing I'd suggest is to rent a cooling system pressure test kit from a major parts store, pressurize the system cold, and check for external leaks.

  4. #3
    basscatt's Avatar
    basscatt is offline Cadillac Owners 10000+ Posts
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    Re: Engine overheating problem

    Quote Originally Posted by MoistCabbage View Post
    It's overheating because it's loosing coolant. There's a leak, and a coolant change and new cap isn't going to fix it.

    The first thing I'd suggest is to rent a cooling system pressure test kit from a major parts store, pressurize the system cold, and check for external leaks.
    --------------------------------------------- find and fix the leak -

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  6. #4
    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: Engine overheating problem

    ............. and you need to read the Northstar cooling system operation sticky posts in Engines: Northstar Performance as well as the cooling system advice way up ^^^ in the top black bar: Cadillac Technical Archive.

    In the Seville, Deville, and Cadillac Tech Tips (Discussions) forums there are many threads concerning your cooling system and its operation.

  7. #5
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Engine overheating problem

    Check the surge tank. They are known to crack and leak. Likewise the radiator side tanks.

    Hint: Dried Dex leaves a chalky white telltale residue.

  8. #6
    DaleCad is offline Cadillac Owners Member
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    Thread Starter

    Re: Engine overheating problem

    No sign of a leak anywhere; no telltale residue. Thanks.

    ----------

    No sign of a leak anywhere. The car sets in the garage for long periods of time, and there is not a drop of coolant anywhere, neither in the engine nor on the floor. The pressure test kit sounds like a good idea. Is this easy to use? I'm not mechanically inclined! Thanks.

  9. #7
    jimsbox is offline Cadillac Owners Enthusiast
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    Re: Engine overheating problem

    You may want to run a block test if using coolant and no residual drops anywhere. Are you seeing any white exhaust? Possible head gasket failure.

  10. #8
    DaleCad is offline Cadillac Owners Member
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    Thread Starter

    Re: Engine overheating problem

    I pray it's not head gasket failure. I had the coolant flushed to avoid that. I've heard so many horror stories of head gasket failure in these Northstar engines. Is that a design flaw or what? I feel like I have a ticking bomb waiting to go off. Wondering if I should ditch the car
    before that happens.

  11. #9
    basscatt's Avatar
    basscatt is offline Cadillac Owners 10000+ Posts
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    Re: Engine overheating problem

    The pressure test kit sounds like a good idea. Is this easy to use?
    YES - and you can usually "rent" one for free at AutoZone -
    or other large chain stores -

    you can do it with the engine OFF - and completely cooled down -

    remove the pressure cap from the SERGE TANK -
    also called the coolant overflow - or reservoir -

    attach the pressure adapter - and pump the system up to 20 PSI -

    the cooling system is a sealed system -
    it should NEVER leak - or require additional coolant -
    and it should never loose pressure -

    in other words - if you pump up the pressure to 20 PSI -
    in a cold system - it should hold that 20 PSI for DAYS -

    if it does loose pressure - there IS a leak - somewhere -

  12. #10
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Engine overheating problem

    Quote Originally Posted by DaleCad View Post
    I pray it's not head gasket failure. I had the coolant flushed to avoid that. I've heard so many horror stories of head gasket failure in these Northstar engines. Is that a design flaw or what? I feel like I have a ticking bomb waiting to go off. Wondering if I should ditch the car
    before that happens.
    Basically, yes. It is a roll of the dice. My neighbor bought my '97 in '06 with 104K. Not sure of the current mileage, but no problems yet that I have heard of.

  13. #11
    DaleCad is offline Cadillac Owners Member
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    Thread Starter

    Re: Engine overheating problem

    Thanks for the tip! I'll look into renting one of these kits and give it a try.

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