2001 Chevrolet Astro Intake Manifold

No, you cannot immerse the assembled upper intake manifold in cleaning solvent.

No, you don't have to remove the upper intake manifold.

You need to disconnect the battery negative cable, remove the engine cover, drain the cooling system, and remove the air cleaner assembly. Then you can remove the air cleaner outlet duct from the throttle body assembly, disconnect the accelerator control cable, and remove the nut holding the air conditioning (AC) hose bracket and the nut holding the engine wiring harness bracket to the intake manifold stud. After disconnecting the electrical connectors, you can remove the ground wire, the nut, and the engine wiring harness bracket. Then you can remove the canister purge valve, the radiator inlet hose, the heater hose, and the water pump inlet hose. After disconnecting the vacuum hose from the intake manifold, you can remove the bolt holding the transmission fluid filler tube, the accelerator control cable bracket, and the distributor. After disconnecting the fuel supply and the return pipes, you can remove the Ignition Control Module (ICM), the exhaust gas recirculation (EGR) valve inlet pipe, the front intake manifold bolt, the drive belt, and the AC compressor side brace. Then you remove the lower intake manifold and clean all sealing surfaces and the intake manifold.