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2000 olds intrigue overheating


So I have a 2000 Oldsmobile Intrigue with about 190k miles. It currently has an overheating problem but first I'll discuss some history:

-It had a previous overheating problem a few months ago that was accompanied by bubbling sounds. We diagnosed this as boiling coolant because the system was not pressurizing due to a leak in the reservoir. We fixed the reservoir leak and pressure tested it to find that the leak was repaired. The bubbling noises stopped and the car no longer overheated.
-The car was then underheating nearly all the time. We diagnosed this as a broken thermostat, probably killed by the overheating that was caused by the leak in the reservoir. We replaced the thermostat and bled/burped the system and now the car does not underheat.

Now the car operates around the half-temp mark and stays very regular except in traffic or parked in the driveway. So it overheats when it is idling. You can rev up the engine in these cases and see the temp gauge fall back down, so it is dependent on RPM only and not on the actual traveling speed of the car. Also at this time the car supplies nice heat to the cabin.

Things to exclude:
The electric fans seem to be working fine and they switch on and off supplying a good deal of wind.
The system was bled/burped.
The system has a new thermostat.
The system does not leak based on a pressure test.
The system has enough coolant.
The system supplies good heat to the cabin.

My guess is that there is a clog/general grossness inside the system someplace or that the water pump is starting to fail, what do you think?


  • Does the radiator have a radiator cap or is the only cap on the reservoir?
  • The problem might caused from erroded impeller blades on the water pump.

    If the vehicle used Dexcool coolant all it's life, one area that gets attacked is the impeller blades on the water pump.

  • edited April 2013
    So when it is overheating in traffic, the radiator fan is coming on full force? And even with the fan on, it still overheats then?

    I guess if I had this problem, I'd suspect an air leak somewhere, the radiator or resevoir cap, hose, gasket, etc. It's possible for a mechanic to pressure test the cooling system to see if it is holding pressure correctly, that might be a good idea. It could be the water pump is just not pumping enough water, or the radiator is clogged up. A radiator shop could probably test the radiator for you, and declog it if necessary. And there's a chance the head gasket is starting to fail. A mechanic can do a chemical test for exhaust gas in the coolant to rule this out or in. If everything turns out negative, then replacing the water pump might be the next thing to try. Make sure the water pump belt is in good shape and tensioned properly of course first. A slipping belt could cause this symptom.
  • @Keith The only cap is on the reservoir.
  • @GeorgeSanJose I already pressure tested the system myself and I used it to diagnose a leak a few months ago which I repaired. It now holds pressure all day. So a clogged radiator can be declogged and doesn't necessarily have to be replaced? By water pump belt do you mean the serpentine belt?
  • Water pump belt is the belt that spins water pump. Do you think serp belt turns water pump? Should you know?
  • Since there is only the cap on the reservoir, there is a small (1/4") line that goes from the top of the reservoir to the radiator hose inlet on the opposite side of the engine. This is a self bleeding system, but if that line gets clogged up, you cannot bleed the system. Make sure it is clear end to end.

    BTW, Dexcool was formulated to reduce erosion on the impeller blades of the water pump. If someone has used another type of antifreeze that contained borates and silicates, then erosion could be a problem. Modern long life antifreezes have eliminated those compounds so it is no longer necessary to use Dexcool, you can use any universal long life antifreeze, but I'd recommend sticking to a major brand though.
  • I recommend using DexCool

    That is what the car is designed to use

    Change it every 5 years

    Which almost nobody does, apparently . . .
  • I don't recommend using Deathcool. Here's what can happen.

    That corrosion/crud can errode the plastic impeller blades on the water pump if it goes unnoticed long enough.

  • To each his own

    We have GM and Ford vehicles in our fleet. And the ones that look like the one in the picture are almost always the ones that NEVER had the coolant serviced.

    That thread is 5 years old, by the way. And the car in question was 3 years old at the time.

    I suspect that the DexCool formulation has changed since then, no matter what GM may say.

    I guarantee you there are no 3 year old GM vehicles in our fleet that have Dexcool that degraded.

    At least not the ones I looked at.

    And that's been hundreds.
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