My 87 T/A stays cool in the city and on the highway its another story. it goes right to the red line. doesnt cross just hugs it. This is only on the highway... the outside temp doesnt effect this at all. 90 or 60 degree weather.. it goes to the red line, anyone have a clue?

Plan A: check for air in the hoses
Plan B: replace radiator cap ($3.50)
Plan C: flush coolant and get some DEX-COOL

Try these step by step until you discover what the problem was. If you still overheat let us know

how do you know that the guage is correct? the sender may be in need of replacement.

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'86 IROC 5-speed
305 LG4
edelbrock performer rpm intake
edelbrock 600 cfm carb
msd pro billet hei
'95 3.23 rearend
hotchkis rear suspension

It's the Airdam. Yours is most likely missing. Happened to me too, car stays beautifully cool and normal until about 50+ mph, then the temperature climbs and keeps climbing until you slow down. It's $20 from the dealer or $1.50 from the junkyard (cheapest fix ever)

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1984 Trans Am, Goodwrench 350, TES Headers, Performer Intake, Flowmaster 80 Series, Holley 600 cfm & vacuum advance, and T5 with short shift

Yep. They have a nasty habit of getting chewed off in parking lots.

Greg,

The lower air deflector (air dam) is a good possibility. The lower radiator support should have the 3" deflector like this:



You should also look for other obstructions to air flow, like debris between the radiator and AC condenser.

Another problem that can cause lack of cooling at RPMs is a lower radiator hose collapse. There is a reinforcement spring inside the lower hose that is supposed to prevent the hose from collapsing under pump suction at highger RPMs. If the hose was replaced without the spring, or if yours has corroded away, you may be experiencing this kind of problem.

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Later,
Vader
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"Let the bodies hit the floor!"
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