99 SLS overheating, need help

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Northstar Engines and System Technical Discussion Discussion, 99 SLS overheating, need help in Cadillac Engine Discussion; I have a 1999 SLS that keeps over heating. I just flushed the coolant and put new coolant in but ...
  1. #1
    dilorenzodesign is offline Cadillac Owners Member
    Automobile(s): 99 Cadillac SLS
    Join Date
    Jun 2013

    99 SLS overheating, need help

    I have a 1999 SLS that keeps over heating. I just flushed the coolant and put new coolant in but the problem still exists. When driving and the car starts to heat up I will crank the heat on, sometimes when it gets hotter the heat blows out cool air. I am trying to pin point the problem but I am not car savy at all so I am doing my best and appreciate any help I can get. When I pull over after the car starts getting hot the coolant bubbles out the coolant cap after I open it a little to release the pressure. Are there any easy steps to pin point the problem so I don't go to a mechanic & have him fix 10 things that isn't the actual problem? I really love my SLS but its now summer & I can't drive my car at all. I've been told it could be a spring in the thermostat and possibly a water pump. Also is it a must to use the GM orange dex cool. Thank you everyone for any help or suggestions given.

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  3. #2
    83CADMAN's Avatar
    83CADMAN is offline Cadillac Owners Fanatic
    Automobile(s): 83 Eldorado, 90 Seville, 94 Concours
    Join Date
    Jun 2009
    Pacific Northwest

    Re: 99 cadillac sls over heating, need help. Thank you

    Sorry man, I hope you didnt pay alot for the car.
    If you are machanical it can be fixed, just be aware of the $$$.
    I'm into mine about $850 (parts, tools & equipment) so far. I still need an assortment of new bolts, sealant, sparkplugs, coolant and a battery. Fortunatley I only payed $600 for the car and it came with a set of new Bridgestone's.
    Good luck.

  4. #3
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with DTS floor shift)
    Join Date
    Jun 2004
    Woodstock Ill.

    Re: 99 cadillac sls over heating, need help. Thank you

    Another '99

    Check the purge line for flow first. If that checks out OK, then borrow a block test kit from AutoZone and just pay fro the test fluid. Run the test after an overheat episode to confirm the failed HG. That's a pretty easy way to pinpoint it.

    No Dex is not a must. Any coolant will do.

  5. #4
    JoeTahoe is offline Cadillac Owners Enthusiast
    Automobile(s): 2001 GMC SLT, Malibu LTZ, 99 STS studded with NP
    Join Date
    Jul 2010
    Central, NY
    Just don't mix the two

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