I have an 89 Camaro Z28 I-ROCZ and my radiator overflow tank was boiling after driving about 10 miles of normal speed driving (following speed limit). The radiator cap is holding the correct amount of pressure and there should be enough coolant in there, yet not too much. What is causing the extra heat?

 

i have seen that happen when there was a issue with a leaking intake gasket.

 

there doesnt seem to be any leakage in that area so i dont think that is the problem. is there any other ideas?

 

Check the basics first.

1st thing I'd do is clear the air out of your system by running the car with raidator cap off.
Check that your hoses aren't collapsed
Check thermostat opens is your top hose hot?
Check primary fan is running when car is up to temp
Replace your radiator cap (how do you know it is ok?)
Has the raidator fluid been changed recently, with the correct mix?

If all that is ok, it may be a more serious problem.

 

8 times out of 10, bubbling (or boiling, since the cap not holding pressure relieved into the overflow is associated with boiling) is usually the result of a old, shitty radiator cap.