I have been having a problem with my car overheating on the highway. I just flushed the radiator, replaced the thermostat, got new cap, and removed the a/c stuff. This helped around town, where i used to run 220 now i run 200. Driving down the highway my car will heat up as high as i will let it. I have had to blast the heat and slow down to keep from hitting 260. help me please, i am stumped!
85 trans am
305tpi
700r4

 

Make sure you have that black plastic air damn beneath your car so air will be forced up to your radiator. I knocked mine off at a 7-11 curb and it overheated on the highway after that happened. I put it back on and it worked again..not sure if this is your problem though

 

check out rsilver's post further down in this forum.........

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"84Z28/'91 305TPI comp cam flowmaster TB coolant bypass/shutoff valve to heater core MAT relocated Ram-Air(home-made) gutted air-box IROC ground effects/wheels GY245/50's 700R4 superior shift kit/ corvette servo(excellent shift kit BTW) Rebuilt engine and transplanted it myself. Love this engine!
LOW performance people should drive low performance vehicles!

 

Yes, that piece of plastic makes a world of difference... (air dam)

 

Absolutely, mine has gotten beat up from some of the driveways i go in and out of here up at school, and i have noticed my car runs a bit warmer on the highway. replace the air dam and u should be fine!

Steve

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86 Firebird, LG4, t-tops, 2.73 open rear, SLP 3 inch cat back exhaust, catco cat, Coming mods: Edlebrock 1 5/8's Headers, 2 inch cowl hood with custon alumin cold air box, 3.42 posi disc rear, T56, and hopefully a new set of heads and a nice CAM!

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It's the air dam. Trans Ams have no grill. 80% of their cooling air is scooped up underneath the car. When the air dam is damaged or knocked off it's not a big deal in the city...but on the highway the airflow and aerodynamics just force the air right past the underneath of the car and none gets scooped up to cool the engine.

 

85,

What Mike means is, you need one of these:




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Later,
Vader
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"Make Me Bad"
Adobe Acrobat Reader 4.0

 

also make sure your car has the scoupe in front of that air dam! my '87 has a molded scoupe that starts on the bottom of the chin spoiler and curves up and back to just in front of the rad.. it helps the fan spoiler to trap more air by creating a larger low-pressure zone.. it's about 2 feet wide and about a feet deep... if you look at it from the fender with your eyes at chin spoiler level it would look sorta like a tilted forward U.. if you can't get an idea of what i mean i can snap a pic with my digital cam for ya

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'86 IROC-Z 305/auto with no cat, performance chip, shift kit, and 4.11s
'87 IROC-Z factory loaded with every option, 84,000 miles

Webmaster: www.IROC-Z.org

 

Just to end some potential confusion. There are 3 pieces to the air dam system.

1. Piece under the nose cone (some cars have it some don't. GM calls this "air deflector".

2. The "air dam strip or spoiler" that Vader is showing you. GM also calls this "air deflector" and note that even on my 86 there are 3 different part numbers for this piece.

3. The piece that bolts to bottom of radiator. GM also calls this "air deflector". This is the most important one and it's the one that I call the air dam.

My own descriptions are:

1. Air dam - bolts to radiator - gotta' have it.
2. Spoiler - runs the width of the front of the car - can get by for a short time without it but it helps.

3. Nose cone diverter - can live without it.

 

Vader, that looks like the lawn edging I have around my shrubs, did you get that at Home Depot?

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"I used to have a handle on life, but then I used it as a plunger and broke it" -The Wave

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GMT,

Good one! It's only lawn edging if I park it on the grass. It's actually an EPDM/neoprene compound that has reinforcement ridges on one side, and a nylon fiber mat molded in. Kind of like a Bridgestone/Firestone tire, but probably better since it's almost a quarter inch thick. It scrapes a bit on steep approaches, but will flex a long way before breaking, unlike the factory PVC molded pieces (which are still under there). FYI - It is a Goodyear product and was available at my local industrial rubber supplier. Industrial rubber? - You know... the kind big companies use to try to screw each other...

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Later,
Vader
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"Make Me Bad"
Adobe Acrobat Reader 4.0

 

Well let me throw this at you....

I have the same problem... my car gets hot onthe highway, and its not that bad around town. It used to run real cool on the highway and get a little hot around town. Now, like I said, it gets hot on the highway and gets only a little hot around town. My coolant levels are fine and my air dam is in place. I think maybe my thermostat is no good. If I change it, I am gonna want to change it to a 160 degree thermostat, but thats pobly not a good idea because NJ winter is coming. Any suggestions for me?

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1989 IROC-Z
350c.i. TPI
rebuilt 700R4 with shift kit
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AOL IMer: JRShotliff

 

HAHAHAHAHAHAHAHA

 

MY 85 TPI TA DOES THE SAME EXACT THING YOURS DOES.I WAS SURPRISED TO FIND OUT THERES THE RAMP LOOKING THING AND THE AIR DAM NOW I JUST GOTTA FIND ONE.ANYONE OUT THERE KNOW WHERE I CAN GET MY HANDS ON ONE??????

 

Dealer. They are real cheap. Under $30

 

Don't rule out a plugged radiator.

Just because it was "flushed" doesn't mean its flowing good.

This will cause an overheating problem at faster speeds but it would cool down as you lowered engine speeds.

Just did a vette with the same symptoms......

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ASE Mechanic/Machinist/Smog Tech

1999 NBM Trans Am
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