I have a 91 rs with 305 and it is overheating. I have put a low 180 thermostat, a new 3 row radiator, a new radiator cap, a new water pump, I flushed the system, and my electric fan is wired to stay on all the time, I have the right amount of coolant in it also. PLEASE HELP ME I NEED THIS CAR TO WORK FOR ME. IT IS MY ONLY VEHICLE.

 

Air Dam?

 

Warm your car up with the cap off and when the thermostat opens up, rev the engine to about 2,000rpm and see if your bottom hose is colllapsing. If it is, replace it with a ribbed hose.
Only other thing I can think of is the thermostat is in backwards.
(copper side should be pointing down) or you might have a crack somewhere or a bad head gasket. In that case you will need to run a compression check on the cylinders and pressure test the cooling system.

 

Check your ignition timing.

 

Reliable gauge?
Is all the air out of the system?
Did you test the T-stat before installing it?

 

Well, I would have to second it on the blown head gasket. If the head gasket is blown into the water jacket all that combustion heat (1100*) will be forced into the cooling system. It won't take to long to get the coolent to 260*.

Auggie

 

It's easy enough to check.
Just start the engine with the radiator cap off, and watch for exhaust gas bubbles.
If in doubt, do a cylinder leakdown test.

 

You can take it to walts and they have a chemical test. turns green if you have a blown head gasket. It cost 30 bucks, but they never charge you if you let them think they will do the work.

 

You sure your guage is right?

Try pulling off the cap and sticking a temperature sensor in there and matching it up with the guage reading.

 

Ya know, there are these laser readers that read exact temps. at whatever you point. Try finding this, and point to certain areas of radiator and hoses, you will be able to find the problem. And if its a bad guage you will feel a lot better when you see the car is running 180-200, and your gauge is saying 260!
An old mechanic, friend of mine from whom I am studying a lot of stuff, told me that your system should be OK if none of the components are spraying coolant all over the place. I agree, but you take it for what its worth. Also replace the sending unit (mounted on the driver side of the heads, and the reder mounted on the pass side of the head, easy to find).
Good luck