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Overheating


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My 98 STS start overheating while the car is moving. When the car is idling and not moving the car does not overheat but soon at I start driving that car will start running warn then the car will run hot after 15-20 mins of driving. To drive the car while it starting to get hot I have to turn on the heat full blast and the car will cool it self of but still runs warm. (The fans do come on) I have flush the coolant and replace the Stat. and Waterpump and Flush the system and add bar's leak stuff. What should I do NEXT.

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Check the front of the radiator / condensor to see if it is full of junk. Other than that you need to replace the radiator.

What do mean by overheat? Do you get a warning message?

Dennis
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Only when the coolant boils over out of the surge tank cap.

That's good, at least you do not loose coolant internally. Slipping waterpump belt? There is a small hose on Northstars which might be plugged. I am trying to find the info in the archives.

The saddest thing in life is wasted talent

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I think adallac is refuring to the purge line. It runs from the water pump housing to the surge tank along the left bank cam cover. Remove it from the surge tank and make sure there is a steady flow from it when the engine is running. If it is plugged, clear it with compressed air and check the end that attatches to the pump housing. It attaches to a hollow bolt. Be sure that is not plugged as well.

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There is a small hose that is hooked to what looks like a bolt near the air intake throttle body. this hose hooks to a pipe that runs between the front rocker cover and intake manifold. It is under the intake cover and comes out as a small tube on the right near the power steering pump. From there it changes back to a hose and goes to the surge tank for the radiator.

With the engine COLD, and the surge tank cap loose, remove the hose from the tank. Be careful, as the tank fitting is plastic. Get a clean soda or water bottle and put the end of the hose in the bottle. Making sure that everything is clear of the serpentine belt, have a helper start the engine and let it idle. You should get a flow of coolant from the hose. If there is no flow, you have found your problem. The fitting that looks like a bolt or the line can plug. The fitting on the surge tank can also be blocked. So if you get a flow from the hose, be sure to check the surge tank fitting for blockage. You will not need to run the engine long, 30 seconds tops.

If any of this return system is blocked, this will give you the symptoms that you describe. I had this exact thing happen to my 1994 SLS and it did precisely what you have happening to you.

The other thing to check would be the water pump drive belt and tensioner.

Good Luck,

Britt

Britt
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Check your lower radiator hose, at idle water runs thru fine but once the motor has rpm's the water pump sucks more water if the hose is bad it will collapse under pressure causing no or little fluid to get thru. Just like trying to suck a Wendy's frosty thru a plastic straw. :lol:

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Did you check your water pump belt and tensioner?

Since you have done so much already, you should have the cooling system presurized and see if it holds pressure to eliminate the possibity that this is a head gasket.

You need something like this:

http://www2.northerntool.com/product-1/200215424.htm

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