How to Replace a Lower Intake Manifold Gasket on a 3800 Series II

The Series II 3.8-liter or 3800 engine was manufactured for several GM vehicles, including the 1996 Buick Regal. The deck height on the Series II is shorter than on the Series I 3800 engine -- the rods are 1 inch shorter and the crankshaft was given a new design. It also got a new intake manifold. The intake is a two-piece manifold, and the upper portion is made of composite material. The material used around the EGR pipe often results in a leak.

Instructions

1

Locate the relay box near the driver's-side fender well. Remove the cover, then using the diagram on the underside of the cover, locate the fuel pump relay. Pull the relay out of its socket. Start the vehicle and let it run until it stalls, to relive pressure in the fuel system. If the vehicle will not start, crank it over five or six times to relieve the pressure.

2

Disconnect the negative battery cable, using the appropriate wrench. Set it aside, ensuring that it does not touch metal. Slide the drain pan under the radiator petcock. Loosen the petcock and allow the coolant to drain. Remove the radiator cap and the radiator will drain faster.

3

Loosen the clamps on the air duct, using the screwdriver, then pull the duct off the air cleaner assembly. Remove the air cleaner assembly and the fuel injector sight shield, using the appropriate sockets. Disconnect the cables from the throttle body and mount bracket, using the screwdriver and pliers.

4

Remove the coolant recovery reservoir, using the appropriate sockets. Remove the inner fender electrical cover on the right side, using the appropriate socket.

5

Loosen the upper radiator hose clamp at the intake manifold, using the screwdriver, then pull the hose off the manifold. Remove the right-rear crossover pipe heat shield, using the appropriate socket. Disconnect the fuel lines from the fuel rail, using the appropriate line wrench. Remove the lines from the cable bracket.

6

Unplug the wiring harness connector on the alternator. Remove the power wire, using the appropriate wrench. Screw the nut back onto the stud, so you don't lose it. Loosen tension on the accessory drive belt by rotating the tensioner pulley toward the center of the engine, using the appropriate socket. Lift the belt off the pulleys. Remove the alternator and its bracket, using the appropriate sockets.

7

Remove the throttle body cable-mounting bracket using the appropriate socket. Mark all vacuum lines and wiring harness connectors, using the tape and marker. Remove all vacuum lines and wiring harness connectors from the top of the engine, including the fuel injector wiring harness connectors.

8

Unbolt the power steering pump and move it aside -- do not remove the power steering hoses. Mark the spark plug wires with the tape and marker, then pull the wires off the spark plugs and set them aside. Loosen the clamp on the coolant bypass hose on the intake manifold. Pull the hose off.

9

Remove the solenoid valve-mounting bracket and the power steering support brace from the intake manifold, using the appropriate sockets. Disconnect the heater pipes from the intake manifold and the front cover, using the appropriate wrench. Remove the alternator support brace from the intake manifold.

10

Remove the thermostat housing and the thermostat, using the appropriate socket. Unplug the electrical connector from the temperature switch, if you haven't done it already. Remove the upper intake manifold bolts, then lift the upper intake manifold off the lower intake manifold. Discard the gaskets.

11

Unbolt and remove the fuel rail and fuel injectors, using the appropriate sockets. Unplug the coolant sensor switch. Remove the manifold end cap cover, then remove the lower intake manifold. Discard the gaskets.

12

Clean the gasket-mating surfaces of the upper and lower intake manifolds, using the shop rags and plastic scraper. Lay the lower intake manifold gaskets onto the engine. Place a 2 mm bead of RTV silicone on the front and rear of the lifter galley, between the heads. Position the lower intake manifold onto the engine. Install the bolts and tighten them to 19 foot-pounds of torque.

13

Circle the bolt holes on the top of the lower intake manifold with a thin layer of RTV silicone. Place RTV on the rest of the gasket-mating surface of the top of the lower intake manifold. Reinstall the fuel rail and injectors while waiting for the RTV to set up. Position the upper intake manifold onto the lower intake manifold.

14

Install the upper intake manifold bolts and tighten them to 88 inch-pounds of torque following the proper sequence. Reinstall the rest of the parts in reverse order of removal. Tighten the power steering support bracket to 37 foot-pounds of torque. Tighten the accessory drive belt tensioner pulley to 33 foot-pounds of torque.

15

Reinstall the fuel pump relay. Reconnect the negative battery cable. Close the radiator petcock and fill the radiator with 50/50 antifreeze. Leave the radiator cap off and start the vehicle. Allow the engine to come to normal operating temperature and check for leaks. Top off the coolant as needed, once the thermostat opens.