How to Replace a 3.4L Intake Gasketby Derek Powlison
General Motors used the 3.4L engine on numerous popular vehicles, including the Pontiac Grand Am, Chevrolet Venture, Pontiac Montana, Chevy Malibu, Olds Silhouette, Oldsmobile Alero and the Buick Rendezvous, just to name a few. Unfortunately, the 3400 engine tends to leak from the lower intake manifold to the cylinder head gasket. The original engineering design used a black nylon frame to position silicone gaskets, sealing the air intake passages and coolant passages to the cylinder head. The black nylon cracks and fails over time, allowing the silicone o-rings to shift and leaks to develop. The most common symptom is coolant mixing into the oil, creating a milk-shake like contamination, evident with the oil cap opened.
Disconnect the negative battery cable to prevent accidental shorting of the electrical system or starting of the vehicle. Open the radiator cap. Raise the vehicle and drain the vehicle's cooling system by opening the radiator drain petcock. Lower the vehicle.
Remove the air intake hose. Disconnect the spark plug wires from the coil pack. Remove the three wire connectors from the coil pack. Disconnect the harnesses from the throttle position sensor, the EGR valve, the coolant temperature sensor, the alternator's positive battery cable, the alternator's voltage regulator and the camshaft position sensor harness located at the front of the intake manifold.
Remove the two 13 mm bolts at the front of the coil pack and the two 13 mm nuts on the back of the coil pack. Remove the coil pack from the vehicle. Remove the two 7 mm screws retaining the MAP sensor to the bracket and remove the MAP sensor. Disconnect the vacuum lines from the upper intake manifold. Remove nut retaining the alternator support strut from the corner of the intake manifold. Remove the 13 mm bolt retaining the alternator to the alternator support strut. Remove the 10mm bolts retaining the EGR valve to the intake manifold by the throttle bore. Remove the EGR valve.
Remove the 13 mm studs and 10 mm bolts retaining the upper intake manifold. Lift the back end of the intake manifold closest to the power steering pump like a hinge to provide access to the 3/8-inch cooling lines under the throttle bore. Loosen the clamps on the coolant lines and remove the upper intake manifold from the vehicle.
Remove the bolt from the back of the alternator on the secondary support strut. Pry the strut away from the alternator. Using a 3/8-inch ratchet inserted into the square hole in the belt tensioner, release the tension from the belt and slide the belt off the water pump. Release the tensioner and remove the ratchet. Remove the belt. Remove the long bolt and nut retaining the alternator and remove the alternator from the vehicle. Using a 15 mm socket, remove the alternator bracket retaining bolts and remove the alternator bracket.
Unplug the injectors. Unplug the power steering pump's proportional steering valve if equipped. Remove the upper engine harness. Remove the fuel lines from the fuel rail. Remove the 10 mm bolts retaining the fuel rail. Pry on the fuel rail gently with a flat head screwdriver to remove the fuel rail and injectors from the vehicle.
Remove the clamps from the coolant bypass hose. Remove the water pump bypass tubes retaining nut by the oil dipstick tube. Remove the 8 mm bolt retaining the bypass tube on top of the water pump housing. Remove the heater hose from the far end of the bypass tube. Loosen the 13 mm nut retaining the bypass tube near the heater hose. Remove the bypass tube assembly from the vehicle. Remove the other heater hose tube from the thermostat housing.
Remove the 8mm bolts retaining the valve covers to the engine. Remove the valve covers. Remove the three 13 mm bolts retaining the power steering pump to the timing cover. The bolts are accessed via the holes in the power steering pump pulley.
Remove the eight 10 mm bolts retaining the lower intake manifold to the engine. Gently pry the intake off the engine. Take the cardboard box and punch four rows of six holes with a phillips screwdriver in it. Space the holes approximately 2 inches apart. Loosen the 10 mm bolts retaining the rocker arms to the cylinder heads. Place the rocker arms and push rods in order in the holes in the cardboard box. The order is critical for re-assembly. Remove the intake gasket.
Remove the bolt retaining the oil pump drive near the transmission. Pry the oil pump drive out of the cylinder block. Clean all gasket mating surfaces of all components. Spray the cylinder head and lifter valley clean of all dirt and debris with brake cleaner. Remove the two bolts retaining the thermostat housing to the lower intake manifold. Replace the thermostat.
Replace the oil pump drive o-ring, the heater hose tube o-ring and the water pump bypass tube o-ring. Place a small-block Chevy paper distributor gasket on the oil pump drive. Reinstall the oil pump drive into the block.
Place the new lower intake manifold gasket into place. Reinstall the push rods and rocker arms. Ensure that they are in the correct order. Reversal of any two could cause severe engine damage. Place a 1/4-inch bead of oil resistant RTV silicone on the block to intake manifold mating surface at both ends of the intake valley. Lower the intake manifold into place. Reinstall the 10 mm retaining bolts.
Reinstall the water pump bypass tube and hose connections. Reinstall the heater hose and upper radiator hose. Reinstall the power steering pump, the alternator bracket, the alternator, and the belt. Reattach the fuel lines. Plug in the harness into the fuel injectors and coolant temperature sensor.
Place new upper intake manifold gaskets into place. Put a new gasket on the EGR tube where it meets the upper intake manifold. Reinstall the upper intake manifold. Reinstall the EGR valve. Reinstall the map sensor and bracket. Reconnect all electrical connections for the EGR valve, MAP sensor, throttle position sensor, camshaft position sensor, the alternator positive cable, the alternator voltage regulator and the variable assist power steering pressure valve if equipped.
Reinstall the coil pack. Connect the three electrical plugs for the power, the communication lines, and the crankshaft position sensor. Reinstall the spark plug wires in proper order. The top of the coil pack is labeled by the factory for the correct firing order. Reinstall all vacuum lines. Reconnect the air intake. Double check to verify all bolts have been reinstalled, all electrical connections have been re-established and all vacuum and coolant lines have been installed.
Lift the vehicle. Drain the oil from the vehicle. Replace the oil filter. Ensure the radiator drain is close. Lower the vehicle.
Using the vacuum cooling system filling kit, draw the engines cooling system to a vacuum. Close the valves and verify the cooling system holds pressure. Fill the cooling system with coolant. Fill the vehicle with motor oil. Reconnect the battery cable.
Start the engine. Allow the vehicle to reach operating temperature. Shut the vehicle off and verify proper coolant and oil levels. Inspect for leaks.
Test drive the vehicle for several miles. Recheck for leaks and proper fluid levels.
- Double-check all electrical connections. Unplugged sensors are the most common cause of the vehicle failing to start after intake gasket repairs.
- Keep the valve push rods in proper order. Reversing an intake and exhaust push rods will severely damage the valve train and require cylinder head removal to repair.
Items you will need
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