Overheating Alero


Old 01-19-07, 07:58 AM
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Join Date: Nov 2004
Location: USA
Posts: 50
Overheating Alero

I'm not even capable of lifting the hood, but I wanted to at least sound like I know what I'm talking about when the mechanic calls me.

My daughter has a 99 Alero, V6, and was driving it around running errands. At the bank drive through, it started to overheat. She let it cool, and brought it home, about two blocks.

I checked the resevoir that evening, and it was still fairly full. The next morning, I drove it to a mechanic, about 20 minutes on the highway, and the temperature startes at the bottom, and slowly made it to about the halfway mark. The gauge never went beyond halfway. I noticed no steam. When I got off the highway, I sat at a light for a minute, and noticed steam coming out. The temp gauge still never went beyond half. I pulled into a lot, and noticed some antifreeze in the engine compartment, but couldn't really tell where the steam was coming from.

Any thoughts?
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Old 01-19-07, 08:49 AM
Join Date: May 2006
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In terms of the antifreeze in the engine compartment, you obviously have a leak. About any where would be suspect - radiator or heater hose sidewall rupture or connections, radiator itself could have a break in it. The radiator cap itself could be leaking, or the line that runs from the radiator to the reservoir. All these things are basic leak points and should be checked regularly.

On the more complicated side, you could have a freeze plug leaking or a head gasket leak. Those are outside the range of the basic DIY'er. You should check for antifreeze in the oil (milky color).

Overheating is most frequently caused by a stuck thermostat. The engine cools and the thermostat closes and won't reopen when the engine is warmed up again. It has either become inoperative due to residue buildup or the expansive properties of the thermo unit has been compromised overtime. They usually cause problems after a complete cool down, but they can act up well after the car has been warmed up as they move constantly to regulate the temperature of the engine.

Your cooling system pulls coolant from the reservoir after cooling cycles by the engine. The coolant in the engine/radiator contracts as it cools, creates a vacuum, and draws from the reservoir. During the warming of the engine, the opposite occurs. If you had a severe leak the vacuum would be broken and the coolant would remain in the reservoir although the engine/radiator was low on antifreeze. Consequently, the engine would overheat.

Hope this helps,

Old 01-19-07, 04:55 PM
Join Date: Apr 2006
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GM product with a V6 overheating????...........First off I'd take a close look at the cooling fan motor and related electrical..........Second.......Take a good look under the intake manifold........#1 problem are blown intake gaskets
Old 01-19-07, 06:19 PM
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Cooling fan was first thing I thought of, too, along with finding the source of the coolant leak.
Old 01-21-07, 05:21 PM
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Join Date: Nov 2004
Location: USA
Posts: 50
It was the water pump, per my mechanic

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