over heating 97 Oldsmobile van

Old 12-17-09, 01:45 PM
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over heating 97 Oldsmobile van

I have changed the heat sensor and thermostat. The engine still overheats. This has a 3.4 V6. The fans seem to be doing their job. Would bad intake manifold gaskets cause the engine to over heat?
Old 12-17-09, 01:48 PM
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Have you checked the radiator? 12+ yrs is plenty of time to gum up a radiator, especially if it hasn't been cleaned regularly and the proper coolant used.
Old 12-17-09, 05:21 PM
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You mean because you think the engine may be running leaner and hotter?

You did put the thermostat back in so the spring faces the engine, right?

Make sure that especially if your car has AC, that the condensor coils in front of the radiator are not plugged with bugs, cottonwood seeds or whatever (same for radiator fins)

It can also be from insufficient circulation caused by a bad air pocket.....(these can be an ongoing occurance if your engine leaks a little coolant and every time the engine tries to draw coolant back into the engine after the engine cools down, it sucks air in instead. You can find this out by observing what the height of the coolant does when hot and cold in your reservoir. If it never goes up and down and stays in the same place, not matter what, and even gets a hair less day by day or a week later, then you know you have some leak that then also is possibly letting in air.)

The air pocket can also be self-caused by you if you opened up the coolant system in any way, like when you replace a hose, stat, or whatever.

You may have a plug you can unscrew out of the thermostat housing, to allow the air to escape.

Or, it can also be caused...(air bubble and extra heat)... if your head gasket is going out and exhaust gases are entering the coolant system. You can tell by seeing if coolant bubbles in your reservoir a little bit after starting your engine. With a good radiator cap, no air pressure should be entering that reservoir. If it is, that means air being pushed into the coolant under 100+psi is opening up the radiator cap and letting it into the reservoir. Good shops have a meter that detects the presence of exhaust gas in your radiator......

or collapsed lower hose,....

...... or a slipping belt(but that be too easy, so doubt that is it). You'd probably hear a belt squeal.

If the engine does not overheat when in town, but does out on the highway, that is your clue that coolant is not making it's way in circles around your engine fast enough. Why?Because at highway speeds when you are fighting the head wind, the engine explosions, that generate heat, need to be bigger, and hence cause more internal heat. If engine passages or radiator is gunked or limed up, or if lower hose is collapsing, then if you remove the radiator cap and allow engine to run and stat open, the coolant will not only launch out of the radiator opening when the thermostat first opens, but continue to do so, since it cannot freely circulate. And if it does that, the one positive note is then you know at least that your water pump is working.

Running a garden hose through the radiator to test it may be a deceptive inconclusive test. I'm not sure, but if you have extreme good water pressure and volume, a short piece of 5/8ths garden hose(to reduce frictional loss, and to generate the max amount of gpms) may help to determine something if you disconnect the lower hose and feed it into the top of the radiator, or into the disconnected- at- the- stat upper radiator hose.

Another test might be to plug the lower exit of the radiator and fill the radiator with a measured amount of water. Then get the specs on what a new radiator like yours should hold. If say yours is below a certain volume threshold, it could be concluded then that it is sufficiently plugged.

If your heater still blows out good heat, and if you are ever in a pickle with overheating, your engine may get a little cooler by turning on the heat and blower to max. if need be, say to make it home. And you are getting too hot, then open the window.

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