Engine - Tappet Noise
No.09-08-87
(C8-09)
P-4733
Date:
December 28, 1987
Index:
ENGINE
Subject:
Tappet Noise
Models:
1988 Equipped With 3.9L or 5.2L Engine
SYMPTOM/CONDITION
Some vehicles equipped with "LA" family engines (3.9L or 5.2L) built prior to October 29, 1987, may exhibit tappet related noise. This condition can be identified as a single or multiple ticking noise originating in one or both cylinder heads. The noise is due to air trapped in the tappet. The causes usually involve one or more of the following:
^ Insufficient oil fill of tappet
^ 1988 roller tappet socket/solid push rod leak condition
^ High clearance/high dry lash
^ Seized/sticky/defective tappet
^ Insufficient oil supply to tappet
DIAGNOSIS
The vehicle should be started cold and operated in park or neutral at idle. Isolate the noise for bank and approximate cylinder location. Remove the cylinder head covers on the noisy bank(s) one at a time. Check the rocker shaft fastener torques. If loose, retorque and re-evaluate the engine noise. Pin point the noise location to cylinder(s) and valve(s) by pushing on each rocker arm individually while the engine is running, noting changes in the noise produced. Note these tappets for future reference.
Operate engine for 30 minutes at varying rpms (900 - 2000), or until noise is gone. Restart engine from cold condition. If noise is still evident, follow directions under the repair procedures.
PARTS REQUIRED
Push Rod PN 4483721
REPAIR PROCEDURE
This procedure involves bleeding and/or replacing the hydraulic tappets and replacing the push rods.
1. Remove cylinder head covers.
2. Remove and discard the push rods from the engine. The removed push rods should be of solid rod construction.
3. Using one of the removed push rods, insert it through the push rod hole in the cylinder head and push down on the push rod socket of each roller tappet. If the roller tappet has entrapped air, the push rod socket will move within the tappet body. Note which roller tappets are "soft." Only these tappets need to be filled manually.
WARNING:
IF, WHEN LOADED, THE PUSH ROD SOCKET DOES NOT MOVE IN THE TAPPET BODY, AND THE PUSH ROD SOCKET IS BELOW THE RETAINING CLIP IN THE BODY, THE ROLLER TAPPET IS PROBABLY DEFECTIVE AND REPLACEMENT IS NECESSARY.
4. Make and use a "Roller Tappet Deaeration Tool" to deaerate and fill "soft" roller tappets (Figure 1). Successful deaeration and filling will yield a "solid" push rod socket that will not move when loaded.
5. Insert the "Roller Tappet Deaeration Tool" through the push rod hole in the cylinder head.
6. Insert the check valve probe through the oil hole in the push rod socket, and push down gently until the push rod socket moves down inside the roller tappet body approximately 1/4" (Figure 2).
7. Fill the exposed cavity in the roller tappet body with l0W30 engine oil. Filling the roller tappet body with oil can be accomplished as follows:
a. Fill the rubber bulb of the "Roller Tappet Deaeration Tool" (Figure 1) with oil before insertion into tappet. After the push rod socket has been moved down inside the tappet body, squeeze the rubber bulb to fill the exposed cavity.
b. Use a pump oil can to fill the exposed cavity with oil after the push rod socket has been depressed.
8. Slightly extract the "Roller Tappet Deaeration Tool" from the tappet body, allowing the push rod socket to rebound to the retaining clip. The oil placed in the tappet body cavity now enters the roller tappet through the hole in the push rod socket.
9. Repeat Steps 6-8 about eight times. This should yield a "solid" push rod socket. Load the socket as described earlier. If the socket is "solid," go to Step 11. If the socket is still "soft," go to Step 10.
10. Rotate the crankshaft 180°. Repeat Steps 6-9. If Step 10 has been performed once, and the tappet, while "soft," has less socket movement than the original condition, then the tappet is considered functional. Go to Step 11 (air will be purged during normal engine operation). If the socket movement is the same or greater than the original condition, it will be necessary to replace the tappet. See appropriate service manual for procedure.
11. Install new push rods, PN 4483721. Install rocker shaft assembly. Torque fasteners to 200 inch pounds.
WARNING:
THE ROCKER ARM SHAFT SHOULD BE TORQUED DOWN SLOWLY, STARTING WITH THE CENTER-M0ST BOLTS. ALLOW 20 MINUTES TAPPET BLEED DOWN TIME AFTER INSTALLATION OF THE ROCKER SHAFTS BEFORE ENGINE OPERATION.
12. Install cylinder head covers.
Engine should be started to verify elimination of tappet noise. If some tappet noise is still present, operate engine for 30 minutes at varying rpms (900 - 2000), or until noise is gone.
POLICY: Reimbursable within the provisions of the warranty
TIME ALLOWANCE:
Labor Operation No. 09-85-02-90 - B Vans 1.9 Hrs.
Cars and Pickups 1.8 Hrs.
FAILURE CODE: 68 - Noisy