Crazy Coolant Temperatures

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HT4100 4.1, 4.5, 4.9 Discussion, Crazy Coolant Temperatures in Cadillac Engine Discussion; Hey there guys.. this site is amazing btw before i get started. So I own a 1992 Eldorado etc w/ ...
  1. #1
    nycgavin is offline Cadillac Owners Member
    Automobile(s): Cadillac
    Join Date
    Feb 2007

    Crazy Coolant Temperatures

    Hey there guys.. this site is amazing btw before i get started.

    So I own a 1992 Eldorado etc w/ the 4.9l, ever since the day I got it, the coolant temperature fluxuates more than my weight Lol. One minute it will be pinned at 85 Celsius, next it will be going from 90-105 and then 5 minutes later will pin itself at 82-85 Celsius. i've replaced a couple of the old cooolant hoses going to and from the radiator, also replaced that cheap T near the firewall, and replaced my thermostat. Its the weirdest problem, mechanic at a local shop just said drive it and forget about the coolant gauge, but I dont want to have the engine blow up on me, so any ideas or help would be greatly appreciated. Let me know if I could give you more information. Thanks

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  3. #2
    carnut is offline Cadillac Owners Master
    Automobile(s): 1988 Allante. 2005 Jag XK8, 1988 Mercedes Benz 300 SE
    Join Date
    Feb 2003

    Re: Crazy Coolant Temperatures

    First make sure no air in the system. Second, replace the radiator cap. If it is stable on the highway at say 85 to 90, but goes to 105 at a stop light, thats normal. The electric fans kick on at approx that temp. Do a search on this forum regarding purging air, burping the system.

  4. #3
    peteski is offline Cadillac Owners Enthusiast
    Automobile(s): 85 Eldo Biarritz
    Join Date
    Dec 2003
    Northeast USA

    Re: Crazy Coolant Temperatures

    How do you know that you can trust the gauge? Maybe the sending unit is intermittant?


  5. #4
    caddydaddy's Avatar
    caddydaddy is offline Cadillac Owners Connoisseur
    Automobile(s): 2005 Escalade 6.0L 2WD, 2007 Jeep Grand Cherokee Limited CRD
    Join Date
    Jan 2003
    Gales Ferry, CT

    Re: Crazy Coolant Temperatures

    The temp readout of my '94 Deville 4.9 goes from around 195 F to 230 F at times. It has done that for years, but the highest I've ever seen it was 235 F or so. It only gets that high idling.

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