1995 Pontiac Grand Prix 1995 Grand Prix cooling system

1995 PONTIAC GRAND PRIX
160,000 MILES • 6 CYL • FWD • AUTOMATIC
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LIBDEMKS
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My 1995 grand prix has started overheating. There is plenty of water in the reservoir, no hoses are leaking. However, if you drive it for about 5 minutes, the temperature gauge starts going up and steam starts coming from under the hood. The really strange part is the fact that if it just sits at idle in the driveway, no problem. I let it just run without driving it in the driveway for 10-15 minutes and the engine hit normal operating temperature and didn't go any higher. Anyone know what could cause this?
Jul 19, 2009 at 9:43 AM
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MMPRINCE4000
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Could be a marginal waterpump, some cars have a plastic impeller, which can work loose from shaft and cause reduced flow.

I would start by having a compression test performed to rule out a headgasket.

If OK, I would drain and flush cooling system, replace thermostat, waterpump, and make sure cooling fans are working.
Jul 20, 2009 at 10:30 AM