Overheating with full coolant
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Cadillac Seville / Cadillac Eldorado Forum Discussion, Overheating with full coolant in Past Cadillac Vehicle Discussion; I have 99 cadillac sls with 105k miles on it. The radiator,cap,thermostat has been replaced brand new earlier this year. ...
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    lacswerve's Avatar
    lacswerve is offline Cadillac Owners Member
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    Exclamation Overheating with full coolant

    I have 99 cadillac sls with 105k miles on it. The radiator,cap,thermostat has been replaced brand new earlier this year. Since then it's been fine, but now its overheating with full 50/50 coolant in it. It then starts to leak coolant on passenger side front end of engine when it started to overheat. I turned the car off but the computer takes over making the engine run idle and radiator fans on. I am curious to if it's a external/internal leak, water pump , thermostat,hose, or cap. No head gasket has been blown yet no visible or audible damage. Besides the leak underneath as stated above.

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    basscatt's Avatar
    basscatt is offline Cadillac Owners Master
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    Re: Overheating with full coolant

    Quote Originally Posted by lacswerve View Post
    I have 99 cadillac sls with 105k miles on it. The radiator,cap,thermostat has been replaced brand new earlier this year. Since then it's been fine, but now its overheating with full 50/50 coolant in it. It then starts to leak coolant on passenger side front end of engine when it started to overheat. I turned the car off but the computer takes over making the engine run idle and radiator fans on. I am curious to if it's a external/internal leak, water pump , thermostat,hose, or cap. No head gasket has been blown yet no visible or audible damage. Besides the leak underneath as stated above.
    ------------------------------
    I turned the car off
    but the computer takes over
    making the engine run idle and radiator fans on

    WHAT?

    I am curious to if it's a external/internal leak,
    pressure test the cooling system WHEN IT IS COLD -

    you can "rent" - for free - a pressure tent kit from autozone -
    or other parts stores -

    check the PURGE LINE for coolant flow -

    if you suspect failed head gaskets -
    do a BLOCK TEST -

  4. #3
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Overheating with full coolant

    How do you know that the HG has not failed? Overheating is one symptom and the '99's are the worst offenders. The coolant "leak" you mention is probably overflow from the surge tank. IF that is the case, then get a block test kit (borrow one from AutoZone and just pay for the test fluid). That will tell you if it is a HG. IF it was not leaking from the overflow, then find and fix the leak point.

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    lacswerve's Avatar
    lacswerve is offline Cadillac Owners Member
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    Re: Overheating with full coolant

    Alright I appreciate it and I assumed it's not a hg because my oil isn't milky.

  6. #5
    Ranger's Avatar
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    Re: Overheating with full coolant

    Northstar do not put coolant in the oil when the HG's fail so forget that.

  7. #6
    MoistCabbage's Avatar
    MoistCabbage is offline Cadillac Owners 10000+ Posts
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    Nor do they smoke in the early stages.

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    lacswerve's Avatar
    lacswerve is offline Cadillac Owners Member
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    Re: Overheating with full coolant

    Ah I see

  9. #8
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    Submariner409 is offline If it won't run, chrome it
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    Re: Overheating with full coolant

    Go down to Engines: Northstar and read the sticky threads on fans, cooling, gauge operation and head gasket failures. That will keep you busy for a while and answer a LOT of questions.

    I see where you tried to login with your never-activated username swervelac a little while back. That has been deleted form the CF database. Please continue to use lacswerve.

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