I have a 2002 Astro AWD.
I know I have a leaking intake gasket, and am in the process of repair.
However I do have a problem Im not sure about.
With the coolant full, I can start up, drive 3 to 5 blocks, and the temp gauge will go sky high. The heater wont put out heat either.
I stop, shut it off, and wait a bit, re start, and the temp goes down, and I will have heat. While I'm driving, the temp will go back up, and I lose heat. I will pull over again, shut it off, and wait, restart, and the temp goes back down, and I have heat.
The water pump isn't leaking. Do I have air in the coolant lines? Would the bad intake gasket, have anything to do with it. As long as I have it apart, I want to fix it, but am not sure what to look for here. I've never experienced it before.
Anyone with the same problem, or someone who knows what to do, I'd greatly appreciate some help here.

 

Sure sounds like air in the coolant lines. It acts as a blocker.

Have you properly bled the cooling system?

Are there bleeder screw valves?

Where you playing with the coolant before you thought of this intake gasket problem?