1987 Pontiac Firebird Only overheats when speeding?

MRDENNIS87

MEMBER
1987 PONTIAC FIREBIRD
V8
2WD
AUTOMATIC
11,200 MILES

Hi, i've been noticing if I go over 55-60 mph and or race it a lil bit either one. It will start to overheat and quickly. Ia m assuming it is because of the air deflector being broke on bottom? An it also losses coolant, no smoek out exhaust, non in oil. Im guessing coolant is form whe nit over heats? ( Has never overheated moking out of hood o rnething ust gets sooo hot n vaporlocks.

Tuesday, January 12th, 2010 AT 3:57 PM

1 Reply

ERNEST CLARK

MECHANIC
1,730 POSTS

Sounds like a bad water pump, stuck thermostat or air/debris in the system.

First, while the engine is cold, pop the radiator cap or surge tank cap. Bring your engine to normal operating temp. (When your fans come on, it's at temp) Then feel the upper and lower radiator hoses. If both are warm, then you know the thermostat is opening. If one is hot, the other not, then the thermostat is stuck closed.

If the thermostat is opening, and before your engine gets too hot, check for the water pump operation/clogged radiator or heater core by reving your engine and watching the coolant for a rise in the radiator or surge tank. (That's easy to verify)

If you don't get a rise, then either the water pump is bad or you have something clogging your system. You'll have to perform a coolant flush and/or replace the pump.

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Wednesday, January 20th, 2010 AT 10:30 AM