I'll assume Lower Intake Gasket, since they tend to cause vacuum leaks. Get a manual from Autozone and expect about 4 hrs labor, you need to take off the upper intake manifold just to replace the Lower Intake Gasket. Probably should change/clean the PCV valve while ur in there. Good luck, man.
if you are going to replace the intake gasket you might as well change the head gaskets at the same time[it will cost you a little now but save you a lot later
take it to a mechanic
there is no lower intake gasket, only a front and rear gasket
i had this problem the intake manifol gasket is blowed
To replace a blown head gasket on a 1998 Chevy Lumina, it would cost between $18 and $174. This depends on the brand part and any labor costs.
how to change timing cover gasket on a 1996 chevy lumina
Remove the intake manifold retaining bolts from your 1996 Chevy Astro Van. Remove the manifold gasket and clean the surface. Reverse the process to install the new intake manifold gasket.
you probably have air in cooling system, which is probably caused by blown head gasket(s). Head gasket and intake gasket on these engines are notorious for failing.
The labor charge to replace and intake manifold gasket, on a 1999 Chevrolet Tahoe, is approximately $180. It takes approximately 2 1/2 hours to replace the gasket.
to replace the intake gasket would be about 4 hours labor. parts would run about $50
If you are sure that it did not freeze and crack the block, Then the intake manifold gasket is leaking. That is a common problem with the vortec Chevy engines. You need to replace the gasket with a factory Chevy gasket from the dealer.
Remove everything on top of the intake (hoses, fuel rails, linkages.) Unbolt the manifold and remove it. Clean the old gasket off and replace it. Reinstall all parts removed to get to the gasket.