I drove my 87 GTA on the highway today for the first time. I had the cruise set at 80mph and I looked down at the gauge and it was 260 so I pulled off to the side of the rode right after i saw that popped the hood and it cooled down rather fast. stll ran about 200 or 220 after that but I couldn't push 55 60 miles and hour other wise the temp ran right up again. It has a new water pump, new radiator, new 195 thermostat, new antifreeze of couse. any ideas why it would be running this way. timing is at 8, new CTS

 

Are your fans working? Also, is your airdam in good shape? Since our cars don't have a grille, the airdam is the only thing pushing air through the radiator at high speed.

 

sounds like an air dam , fan problem to me . do a search on both , i'm sure you will find a solution . good luck .

 

Ya I just ordered the air dam for it this morning. One f the fans doesn't work. Iwas thinking about replacing them is there an aftermarket setup that would work better.

 

Both the fans work I jumped power to them. The one that is not turning on is the pass side one.

 

The fans won't do any good at 80 mph.
You need to get the air dam on. Then see how it does.
If you want to, a scoop or cowl hood will help.

 

Just check the fans.

 

I also thought that your fan is the culprit for this problem but since you're at 80mph I totally agree that it's the air dam dude. The front end blocks most of the air from entering below the radiator, reducing air pressure underneath at the front.Try to check your cooling system regularly just a piece of advice.

 

I had the same problem, Under 40 MPH, the car ran fine, but over about 60, the temp guage just marched right up. My air dam under the chin was tweaked in a few places but didn't really look bad, but at speed the air pressure bent just bent it backwards and all the air went under the car instead of through the radiator. I got some Safety wire and drilled the dam and wired it so it 'scoops forward" a bit, doesn't let the air pressure bend it backwards, and the problem disappeared.

TA