I have a 86 Trans Am, The Problem is with overheating, ill start and drive and it will be a 220 on the temp guage for a while, but when i get on the high way and start to go fast it starts to go up, it usually sits right in the middle of 220 and the red zone on the temp guage sometimes it does this with regular road driving as well and when I go faster like 70 or 80 my t/a gets closer to the redzone, but when i slow my vehivle down it will go back down to 220 and sometimes just a little below 220, I replaced the thermostat and radaitor and it is still doing it, and my antifreeze always appears to be full, when i popped open the hood while the temp guage was up the fan seemed to be working fine, I really wanna find out the problem is before I ruin my engine, could someone please help!!!!!!!!!!!!!

 

make sure the air dam is there. make sure the condenser (if applicable) is not causing air blockage.

 

check your timing and make sure you don't have an air pocket...

 

how exactly do u do that, but i do think my timing is off

 

Something to keep in mind........
City overheating is usually an Airflow issue
Highway overheating is usually a Coolant flow issue
So....
A plugged rad 'may' stay cool enough in the city but overheat on the highway under really heavy loads
A bad Fan may not work in the City but your system will work great when you go above low City speeds or on the Hiway.
Decide when your system runs Hot.
Again.....the general rule is
Overheat in the City....not enough Air Flow.....bad air flow or other issues related to fans
Overheat on the Highway....not enough Coolant Flow or low system blocked rad low coolant list goes on

 

Sorry, after re-reading your post........
It sounds like your Radiator may be plugged
When you drive in the City it acts OK, but when you go on the Highway it gets hot
The faster you go the Hotter it gets
You back off the throttle it cools down
If this is your situation, your Rad is Plugged
It can't flow enough Coolant to cool the demand you are putting on the Engine and it will heat up
Fix/Replace the Rad
Good Luck
Greg