Question about 2000 Pontiac Grand Prix

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2000 Grand Prix losing coolant

I have a 200 Grand Prix that continuously loses coolant. Not a lot of coolant but I seem to have to top it up every couple of weeks. When the coolant gets low, the temperature gauge acts erratic and goes very high then drops back to normal. I'm guessing that the sensor must be reading incorrectly because of the large swings in temperature - I can't see the coolant changing temperature this quickly. (Maybe the sensor is no longer in the coolant when it gets low?)

Coolant does not seem to be leaking into the cylinders as the oil does not appear cloudy and there are no indications of a coolant leak to the outside of the engine.

Can't smell coolant in the car so it doesn't seem like it's the heater core either.

Any ideas?? Where could the coolant be going?

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  • Pontiac Master
  • 71,525 Answers

This all sounds like a leaking head gasket, the fast guage swing is caused by air pockets around the temp sensor.

Posted on Nov 06, 2008

  • yadayada
    yadayada Nov 06, 2008 claims they have factory repair & owners manuals, they have nothing of the sort. Some experts may have a small personnel library of manuals. Experts are not employed by, we help free of charge as much as we can with the general automotive knowledge we have learned while working as auto technicians, specific test values, repair procedures and illustrations are unique to each car line, these are not in most cases available to us. Thanks for using FixYa!

  • Wolfman Thomas
    Wolfman Thomas Apr 16, 2015

    A bad radiator will cause coolant water go directly into your transmission


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  • Pontiac Master
  • 451 Answers

Dennis is right on target. I had the same problem and had to change the intake manifold gasket. Sad thing pontiac knew this was a problem but did not recall. They had the cheap plastic gasket which is known to deteriorate. I replaced it with a copper gasket and problem solved. After you do this then add your coolant and don't forget to bleed the air out of the system or the temperature will climb. How do I know this? I fogot to bleed system and the car overheated. The bleed screw is on the top of the manifold and should be blue in color. Good luck

Posted on Apr 18, 2015

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