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Overheating quetions


wawazat

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Hello all, this will be my 1st post and unfortunately, I have a problem.

I have a 1998 STS, and about a month ago, it began to run hot (1st time ever the gauge went past the straight up position) and I got the "idle engine" message. I idled for about 20 minutes and brought the car back home, but all the way home (20 miles), about every 6 miles or so, the temp gauge would go two notches past center, and then back to center after about a minute.

The car was bought in Feb. of this year and had 63,000 miles then, and 72,000 now.

I decided to replace the antifreeze, and for peace of mind, the thermostat and pressure cap.

After flushing the engine with distilled water, adding fresh coolant with the recommended tabs, replacing the thermostat and pressure cap, the car still overheats. What is so annoying is the way it does it. I can drive for 10 miles at normal operating temperature, then, with no warning, the gauge starts to go to the right. Sometimes it will go back, and sometimes it doesn't.

The radiator is brand new and a new water pump was installed by the dealer in March. There are absolutely no leaks of any kind to be found anywhere.

The water pump belt and tensioner are fine, as are the cooling fans and their operation. There are no obstructions or air pockets in the system, and the purge line is clear. Even the heater core was checked for flow and it is fine. The surge tank level is consistent, going down as the RPM's increase and rising again as they decrease.

From the condition of the car (1 previous owner) I don't believe it was beat on, ill-treated or otherwise. It was always dealer serviced (at least that's what carfax and the dealer say).

I was going to buy the test kit to see if actually there could be exhaust gas in the coolant, but at this point, should I even bother? The $50 for the kit could go toward the head gaskets, if I need them. By the way, all the replaced parts are GM, including the radiator.

Is there anythng else I should check? Any input would be appreciated.

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I can only think of one other thing, and that is the "hollow bolt" in the throttle body. This showed up about 6 months ago after I went on a rant about an engine being in need of a head gasket replacement. Sometimes this thing gets plugged and won't let the engine remove that last little bit of air. I don't really like the sound of the coolant in the reservoir changing level so quickly, to me it sounds like compressable air in the cooling system.

Remember to NOT blow out the bolt with compressed air, just remove it to see if it is plugged by a peice of rubber or something.

I have no idea where this thing is exactly, nor if it is even on your particular model, all I know is that it bit me before, and I would check it.

Hopefully others will chime in with more info.

Never underestimate the amount of a persons greed.

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.... The surge tank level is consistent, going down as the RPM's increase and rising again as they decrease.

The coolant reservoir level should be constant; the fluid going into the reservoir is immediately pulled back into circulation by the water pump. One of the main functions of the reservoir is to provide an escape path for air (the reservoir is the highest point in the cooling system plumbing).

If you are not losing coolant, you can forget about head gaskets. If you are losing coolant, triple check for external leaks.

You should check the plumbing from the hollow bolt, through the throttle body, to the rubber hose at the top of the reservoir. That complete line should flow freely with a small stream at idle.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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