How to Replace the Intake Manifold on a Chevy Astro

The intake manifold in your Chevy Astro van distributes the fuel/air mixture to the cylinder heads. Replacing one is usually a job best left to professionals, as is the case with most modern-day engine components. One of the most important things to remember is how all the parts connect to the manifold.

Removing the Old Manifold

Disconnect the van's negative battery cable. Remove the engine cover. Push the front seats back, remove the engine panel's lower extension, disengage any support rods and floor ducting, loosen the retaining screws and unlock the bottom latches. Disconnect the VC valve and hose from the manifold.

Drain the cooling system. Place a container under the drain plug at the radiator, and remove the plug to drain the coolant from the radiator. Repeat with the same container under the coolant drain plug at the engine block.

Detach the fuel lines, vacuum lines and wire leads from the fuel injection assembly. Plug the fuel lines with rubber so the fuel won't get contaminated. Disconnect the fuel injection throttle linkage, cruise control and TV linkage, and all other vacuum lines and wires connected to manifold components. Make sure you know how and where everything is reconnected.

Remove the ignition coil from the engine by unplugging its wire and electrical leads and removing its mounting nuts. Unbolt the alternator and its bracket, and set it out of the way.

Remove the manifold's mounting bolts and separate it from the cylinder head. Don't pry the manifold off the head, or you may damage the sealing surface. Scrape the old gasket material off the mating surface.

Installing the New Manifold

Remove all components that are still attached to the old manifold, and connect them to the new one.

Clean the cylinder head with lacquer thinner or acetone. Do the same to the new manifold's gasket surface if needed.

Apply a thin coat of RTV sealant to the mating surfaces of both the manifold and the cylinder head. Don't use too much sealant; make sure it won't go into the air or coolant passages after installation. Place a new gasket on the manifold.

Hold the manifold against the cylinder head, and install the bolts by hand. Tighten the bolts with the wrench in a specific order: Start with the two bolts on the top edge, then the two on the bottom corners, followed by the one on the top left corner and the two middle bolts at the bottom.

Reinstall all parts and components in reverse order of removal. Refill the radiator; use fresh engine coolant if the old coolant is contaminated in any way.