Question about 1999 Cadillac DeVille

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Coolant temp. raising. no coolant loss.

1st, waqs losing coolant. found it was the tank cap. replaced and pressure tested the system. next found a leak from a silicone hose under the egr valve. replaced. ran the car, and the tempurature was raising! above 45 mph the temp would raise to 228degrees. driving thru the city temp would drop and stay at about 217degrees. which is funny seeing how the faster the car is moving the lower the temp should drop. but it was doing the exact opposite. replaced the thermostat and water pump. will drive like a dream on the way into work. 196/197 on the freeway and raise up to about 206degrees in between stop lights. when driving home will start the same as in the morning. then if i am slowed by some traffic, or what have you, temp will get up to 228degrees. shut a/c off and temp will drop stay at about 215-219 degrees. fans are cycling on and off. my 1st question is what is the standard oem operating tempurature for this car, and 2nd, what caould be the fix?? please help! the car is a 1999 cadillac sedan deville. 113,000 miles. had only 1 previous owner.

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  • jtre2nd Jul 08, 2008


  • jtre2nd Jul 09, 2008

    when i turn the car on it starts right up no rough idling. there is no coolant loss in system. no "mayonaise" in oil. no white smoke from tailpipe. will try the steops. i am now currently leaning towards the fans. to me they seem to be weak. but they do cycle. at idle nothing on they kick on at about 222degrees shut off at 212. as soon as the a/c is kicked on, they will work. not too sure but they should be a 3 step(cycle) fans. need to know if there is a way to trouble shoot fans. also just replaced the 3 relays for the fans. was wondering if theres a way to further diagnose them, and/or what are the temps or specs as when they should kick on. thanks for the help!

  • nlimberis Jan 11, 2009

    I am trying to change the water pump on my 1999 cadillac deville and I have the tool and it seems to keep slipping what do I do now?



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First with the car off and cool squeeze bottom radiator hose with your hand then do the top,this burps any air out of the system,of course have the cap open,if this doesnt solve the problem its your radiator cores are block as you speed up its trying to force coolant thru a blocked core and temperature rises,you can pull your raidiator and have it cored at a radiator shop,cheeper than buying new

Posted on Jul 07, 2008

  • derek martin Jul 08, 2008

    then its the water pump,the propeller inside is faulty,need to rteplace pump

  • derek martin Jul 08, 2008

    when you start the car,with a glove on or a rag squeeze the top hose you should develop pressure in the hose,when your fans kick on you should lose pressure in the hose (thermostat opens) check bottom hose to feel if antifreeze is running thru,If it is running thru then its a head gasket,sorry about the last comment I missed that you changed water pump,keep checking the oil dipstick to make sure your not getting antifreeze in your oil,it will turn your oil a white milky color,also if your car starts to smoke out of the exaust white smoke



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