As the title says, recently my z28 has started to overheat under low-rpm conditions, especially in 6th gear on the highway (where I first noticed it). Getting the rpm's up above 2.5k or so cools the engine down again without problem. If I come up to a stoplight or something that causes the rpm's to fall again the engine rapidly overheats within a matter of seconds. Thoughts?

 

Sounds like the water pump needs replaced. Maybe the WP drive is slipping and isn't turning the pump until you get the RPM's up. I would pull the pump and check for signs of the shaft slipping.

 

Cracked head or headgasket. When engine is cool, remove radiator cap and start engine, if you see bubbles after a few minuets, you have one or the other.

SteveC

 

Will I need to bleed the air out of the system after running it with the cap off?

 

No you won't.

SteveC

 

No bubbles, rather relieved.

 

Sad. This is the same problem that i have with my camaro. I turn the engine on and wait a few minutes and the bubbles apperar. No much bubbles, just a litlle ones. How bad is?