70 coupe running hot
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RWD 19xx-1984 DeVille and Fleetwood,
1985-1996 Fleetwood and Brougham Forum Discussion, 70 coupe running hot in Past Cadillac Vehicle Discussion; hello, my 70 coupe has an aftermarket temp gauge that seems to read hot. when i drive the car it ...
  1. #1
    marcscaddy75 is offline Cadillac Owners Member
    Automobile(s): 1970 cadillac coupe deville
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    70 coupe running hot

    hello, my 70 coupe has an aftermarket temp gauge that seems to read hot. when i drive the car it runs at approx 190 degrees but at idle it can creep up to 230. car doesnt overheat and i have a temp gauge radiator cap that doesnt read hot either. what is the proper operating temp the coolant should be at? currently i have a 160 degree thermostat in the car as well as an aditional electric fan for radiator. Any advice?? thanks

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  3. #2
    sven914 is offline Cadillac Owners Connoisseur
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    Re: 70 coupe running hot

    The radiator cap gauges are inaccurate because they only read the coolant temp as it exits the engine. I have one and it always 10-20º off from my gauge (aftermarket digital).

    It is normal for the temperature to increase at idle, but a 160º thermostat should allow the coolant to cycle fast enough to keep the temperature around 210º. I would say your gauge is off; it could be the gauge itself, or the way you have the sender mounted in the coolant passage. To be safe, you could get an infrared heat gun at Autozone or Sears, and use it to scan the engine for hot spots.

  4. #3
    DouglasJRizzo is offline Cadillac Owners Enthusiast
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    Re: 70 coupe running hot

    You may want to check for a faulty thermostat. If it's slow opening, doesn't open all the way or stuck in one spot, it could cause a hot running engine.

  5. #4
    marcscaddy75 is offline Cadillac Owners Member
    Automobile(s): 1970 cadillac coupe deville
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    Re: 70 coupe running hot

    so do you think that if my gauge in the car is accurate, then if it goes up to 210 to 230 at an idle then i am fine and not at risk of overheating?

  6. #5
    sven914 is offline Cadillac Owners Connoisseur
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    Re: 70 coupe running hot

    The 472 was designed to run cool, so going up that high too often could cause strain. I don't know where the factory "WATER-TEMP" lamp was set to come on, but would say somewhere in the 240-250º range. At that point, damage has already been done to your engine.

  7. #6
    CADforce69 is offline Cadillac Owners Connoisseur
    Automobile(s): Cadillac Sedan de Ville 1969, Dodge 3700GT '73, Audi A3 1.8T
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    Re: 70 coupe running hot

    As service manual says, water temp should light when engine temp. is 264ºF, what I think is too late, and engine block temp. glows when temperature is 280º so you should be burning head gaskets. Best way to be sure is buying or borrowing an infra-red -like Sven has mentioned- or a laser temp. gun to compare at different gauge measurements which is the real temp. measured by the gun on the heads. This way you´ll have a reliable reference.

    My advice is, if your water temp is on, stop car ASAP and open hood to help engine losing heat. Don´t go on until Metal temp light glows as then your engine can fry.

  8. #7
    Fleetwood70 is offline Cadillac Owners Fanatic
    Automobile(s): 1970 Fleetwood 60-Special, 03 DHS
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    Re: 70 coupe running hot

    Connect your distributor vacuum advance to manifold vacuum, if you haven't done so already. Should help engine run cooler, especially at idle.

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