To remove the intake manifold, first disconnect the negative battery cable and drain the cooling system. Remove the air cleaner assembly, throttle body (if intending to resurface or replace the manifold), alternator rear brace, and, on air-conditioned models, move the compressor out of the way by removing the brackets. Detach the Electronic Spark Control (ESC) module bracket on the side of the manifold, remove the idler pulley rear bracket, and label and disconnect any fuel lines, wires, and vacuum hoses connected to the intake manifold, checking for interference with other components such as the transmission dipstick tube, EGA system, PCV system, and power brake lines. Detach the upper radiator hose from the thermostat housing cover and, if present, disconnect the heater fitting in the intake manifold. Remove the distributor and ignition coil wires. Loosen the manifold mounting bolts incrementally until they can be removed by hand, using caution not to damage the gasket sealing surfaces. A pry bar can be placed under the cast-in lug near the thermostat housing to aid in prying up the front of the manifold if it is stuck. During installation, ensure that the cylinder heads, block, and manifold mating surfaces are meticulously clean, removing any sealant and old gasket material with a gasket scraper and wiping the surfaces with lacquer thinner or acetone. Cover the lifter valley with shop rags to prevent debris from entering the engine, and clean the bolt holes using a tap and compressed air. Apply a thin coat of ATV sealant around the coolant passage holes on the cylinder head side of the new intake manifold gaskets and position the gaskets on the cylinder heads, ensuring correct alignment and orientation. On 7.4L V8 engines, install front and rear end seals on the block and apply a 3/16-inch bead of ATV sealant to each corner of the end seals where they meet the gaskets. Use a tap of the correct size to chase the threads in the bolt holes and apply Loctite 242 or its equivalent to the manifold bolt threads before installing and tightening the bolts following the specified torque sequence. Finally, complete the reinstallation steps in reverse order, start the engine, and carefully inspect for oil, vacuum, and coolant leaks at the intake manifold joints. For upper intake manifold removal on 1996 and later models, disconnect the negative battery cable, drain the cooling system, and remove the air cleaner assembly, duct, and any interfering wiring, throttle and cruise control cables and brackets, and fuel lines (on V6 and small-block VB engines). Remove the coil and bracket, and on 7.4L V8 models, remove the PCV hose, EGR inlet tube, purge solenoid with connectors, and any interfering spark plug wires. To install the upper intake manifold, position the gasket and manifold, tighten the bolts in two steps using a criss-cross pattern, and follow with the remaining installation steps in reverse order.
Posted by GMPartsGiant Specialist