ABOVE NORMAL VALVE TRAIN NOISE CAMSHAFT SEIZED/LOW OIL PRESS.
VEHICLES AFFECTED: 1987-89 N W/2.3L
The 2.3L engine utilizes an oil flow check valve which is a press fit into the top of the cylinder block to the right of number one cylinder. Refer to Figure 1, Item 5. The valve's primary function is to retain engine oil in the cylinder head and camshaft carriers after the engine has been shut off. The retained oil is then immediately available to valve train components when the engine is started.
A malfunctioning check valve may result in the following:
CONDITION:
--------- 1. Above normal valve train noise on start up. Valve train noise diminishes as engine runs.
POSSIBLE CAUSE:
An engine that exhibits above normal valve train noise (clatter) on start up, then quiets down, may be the result of the ball check not seating properly within the check valve. This condition would allow oil in the cylinder head and camshaft carriers to drain back to the crankcase after the engine is shut off.
CORRECTION:
---------- Replace the oil flow check valve. Refer to "OIL Flow Check Valve Replacement" procedure in this bulletin.
Notice: Above normal valve train noise on start up may be the result of oil drain back from the engine block itself. Prior to replacing the check valve, install a PF47 oil filter. The PF47 has an internal anti-drain back valve that helps keep the engine block oil galleries full.
CONDITION:
---------- 2. Above normal valve train noise oil pressure light on, no or low oil pressure.
POSSIBLE CAUSE:
Oil flow restricted to cylinder head and valve train due to ball check in valve stuck closed.
This condition can be verified by comparing engine oil pressure taken at the exhaust cam carrier (sending unit location) and at the oil filter. Refer to the procedure in this bulletin for: "Checking Engine Oil Pressure". If pressure at the cam carrier is low or zero but adequate at the filter, (minimum 275 kpa (40 PSI) with cold engine) then the check valve is the probable cause.
CORRECTION:
----------- Replace oil flow check valve. Inspect and replace any damaged valve train components. Refer to "Oil Flow Check Valve Replacement" procedure in this bulletin.
CONDITION:
---------- 3. Engine can be turned over but will not start. Power steering pump pulley (on end of intake cam) does not turn when engine is turned over.
POSSIBLE CAUSE:
Intake cam, intake cam sprocket or sprocket dowel pin broken resulting from restricted oil flow due to ball check in valve stuck closed.
CORRECTION:
---------- Replace oil flow check valve. Inspect and replace any damaged valve train components. Refer to "Oil Flow Check Valve Replacement" procedure in this bulletin.
CONDITION:
--------- 4. Engine can not be turned over.
POSSIBLE CAUSE:
Intake or exhaust camshaft seized in carrier resulting from restricted oil flow due to ball check in valve stuck closed.
CORRECTION:
---------- Replace oil flow check valve. Inspect and replace any damaged valve train components. Refer to "Oil Flow Check Valve Replacement" procedure in this bulletin.
CHECKING ENGINE OIL PRESSURE
IMPORTANT: Prior to checking engine oil pressure, insure engine oil is at the correct level.
Oil pressure test at oil filter:
1. Disconnect cooling fan connector.
CAUTION:
------- To prevent injury, the engine cooling fan must be disconnected when servicing oil filter area.
2. Remove oil filter from engine.
3. Install oil pressure tester J-25087-C or equivalent to filter base. Refer to Figure 2.
4. Start engine and observe oil pressure. Minimum pressure cold engine: 275 kpa (40 PSI.)
5. Remove pressure tester.
6. Install oil filter.
7. Connect cooling fan connector.
8. Check for correct engine oil level. Adjust if necessary.
OIL PRESSURE TEST AT EXHAUST CAM CARRIER.
1. Remove oil pressure switch/sensor from end of exhaust cam carrier.
2. Install an accurate engine oil pressure gauge.
3. Start engine and observe oil pressure. Minimum pressure cold engine: 275 kpa (40 PSI.)
4. Remove pressure tester and install switch/sensor.
IMPORTANT: If pressure is normal at the filter base but low or zero at the exhaust cam carrier the oil flow check valve is the probable cause.
If pressure is low or zero at the filter base, the oil pump is the probable cause.
OIL FLOW CHECK VALVE REMOVAL AND INSTALLATION
The oil flow check valve is located in the top of the block to the right of number one cylinder. The valve is press fit into the block and can be removed, and a new valve installed using the oil flow check valve removal tool, J 38123 (if available) following the procedure outlined on page 6A7-48 in the 1989 "N" Service Manual.
If tool J-38123 is not available, it will be necessary to fabricate a check valve removal tool using a 3/16 x 4 inch round head machine screw.
Modify the Screw:
IMPORTANT: To aid in screw modification, it is recommended that a new check valve, part number 22548701 be used as a guide while performing the follwing two steps.
1. Parallel to the screwdriver slot, evenly grind both sides of the head of the screw until the screw head can be inserted into and past the two indentations in the check valve. Refer to Figure 3.
2. With the screw head inserted into check valve past the valve indentations as described in Step 1, rotate the screw 90 degrees to engage the screw head under the indentations.
IMPORTANT: ---------- If the screw cannot be rotated to engage the head under the valve indentations, very lightly grind the screw head outside diameter until the screw can be rotated (with some friction).
OIL FLOW CHECK VALVE REMOVAL USING MODIFIED SCREW:
1. Remove cylinder head. Refer to the Service manaul section
2. Carefully soak up any oil remaining in the check valve with shop or paper towel.
3. Carefully insert the modified screw head into the check valve past the indentations. Rotate screw 90 degrees to engage the screw head under valve indentations. Refer to Figure 3.
Notice:
Use care not to let the modified screw head impact the ball check in the valve. Impact could cause the ball check to disengage from the valve allowing it to drop into the engine oil galleries.
4. Use a slide hammer or other suitable tool on the threaded end of the modified screw to pull the check valve from its bore.
IMPORTANT: --------- If the ball check is missing from the valve when removed, it must be located and removed from the engine prior to installation of a new check valve. If the ball is not removed from the engine and the engine is started, a "no engine oil pressure" condition will likely result. Refer to "Check Valve Ball Removal From Oil Galleries" procedure in this bulletin.
Installation:
1. Place new check valve, part number 22548701 into valve bore in block.
2. Use appropriate size socket or flat nose punch to drive valve. Lightly tap socket/punch to seat valve in bore.
IMPORTANT: --------- When tapping socket or punch to seat valve in bore, there will be a distinct change of sound as valve seats. A properly seated valve check should not protrude above the top of the block surface and should be slightly below it.
CHECK VALVE BALL REMOVAL FROM OIL GALLERIES:
The following procedures can be used (as required) to remove the check valve ball check from engine oil galleries. These procedures (A through C) are listed in sequence and should be followed accordingly.
Procedure A.
1. Insert a narrow magnet (or screwdriver with a magnet on top of the screwdriver shank) into the check valve bore in the block.
2. If magnet contacts ball check, ball can be removed.
Procedure B
1. Remove timing chain housing from engine compartment and remove front oil gallery plug. Refer to Service Manual.
2. Insert a narrow magnet with flexible handle into the front oil gallery. Push the magnet to the end of the gallery. If magnet contacts ball check, ball can be removed.
Procedure C
1. Drain oil and remove oil pan. Refer to Service Manual.
2. With timing chain housing and front oil gallery plug removed, insert magnet into gallery approximately 25.4 mm (1 inch) to position magnet over Number 1 bearing oil feed passage.
3. Remove Number 1 main bearing cap.
4. Rotate crankshaft so the oil feed hole in Number 1 main journal is approximately at the 4:00 o'clock position as viewed from the front (crankshaft snout end) of the engine.
IMPORTANT: --------- Placing the crankshaft main journal oil feed hole at the 4:00 o'clock position allows the journal hole to line up with the oil hole in the upper bearing.
5. Verify that the oil feed hole in the crankshaft journal is lined up with the hole in the upper bearing by inserting a small plastic straw thru the crankshaft journal and bearing oil feed hole.
NOTICE:
Do not use a metal tool to align the crankshaft journal and upper bearing hole or bearing damage could result.
Important: When the crankshaft journal and upper bearinq oil holes are aligned, the ball check (if in the main bearing oil feed passage) may be visible when looking through the crankshaft journal hole.
6. With a rubber tipped air gun, blow compressed air through Number 1 crankshaft main bearing journal oil feed hole to force ball to magnet.
If ball cannot be located, repeat procedure C, steps 3 through 6 at the other crankshaft main journals in sequence of 5,4, 3, 2 until the ball is recovered.
PARTS INFORMATION
Parts required to perform the repair described in this bulletin are listed below.
DESCRIPTION PART NUMBER ----------- ----------- Oil Flow Check Valve 22548701 Gasket Kit, Cylinder Head 22535452
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.
