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ENGINE
ROCKER ARM SHAFT/ ROCKER ARM / LASH ADJUSTER (Continued)
POSSIBLE CAUSES
1. Engine oil level—too high or too low. This may cause
aerated oil to enter the adjusters and cause them to be
spongy.
2. Insufficient running time after rebuilding cylinder
head.
3. Air trapped in lash adjuster (after 1 hour run time).
4. Low oil pressure
5. Oil passage to cylinder head(s) plugged with debris.
6. Worn valve guide(s).
7. Air injested into oil due to broken or cracked oil
pump pickup tube.
8. Collapsed lash adjuster due to debris injestion.
9. Intake rocker arm roller clevis ear(s) contacting
camshaft bearing journal(s) on side.
*Lash adjusters are serviced with the rocker arms—do not disassemble.
STANDARD PROCEDURE - HYDRAULIC LASH
ADJUSTER BLEEDING
Use this procedure to manually bleed aerated oil
from the lash adjuster and remove sponginess.
(1) Run the engine, bringing it to operating tem-
perature in order to freshly pressurize and warm the
valvetrain system oil supply.
(2) Remove cylinder head cover(s).
(3) Ensure the rocker arm is positioned on the
base circle of the cam (Fig. 54). Rotate engine as nec-
essary.
LASH ADJUSTER (TAPPET) NOISE CHART
CORRECTION
1. Check and correct engine oil level.
2. Low speed running of up to 1 hour may be required
to fully evacuate trapped air from the valve train
system. During this time, turn engine off and let set for
a few minutes before restarting. Repeat this several
times after engine has reached normal operating
temperature.
3. See below:
(a) Check lash adjusters for sponginess while installed
in cylinder head. Depress part of rocker arm over
adjuster. Normal adjusters should feel very firm. Very
spongy adjusters can be bottomed out easily.
(b) Before proceeding, perform Lash Adjuster Bleeding
procedure.
(c) If lash adjuster(s) are still spongy, replace with new
adjuster/rocker arm assembly*.
4. See below:
(a) Check and correct engine oil level.
(b) Check engine oil pressure.
(c) Check for excessive bearing clearance and correct.
(d) Check for worn oil pump.
5. Check cylinder head oil passages and cylinder head
gasket restrictor for blockage. Clean or replace as
necessary.
6. Ream guide(s) and replace valve(s) with oversize
valves and seal(s).
7. Inspect pickup tube and replace as necessary.
8. Clean debris from engine and replace lash
adjuster/rocker assembly*.
9. Inspect camshaft end play and all valve train
components for wear. Replace as necessary.
(4) For intake rocker arm positions:
(a) Adjust Special Tool 8351 Release Probe's
gauge pin to extend approximately 20 mm (0.787
in.). Then, carefully insert the release probe gauge
pin into the lash adjuster service access hole (Fig.
55).
CAUTION: If probe tip breaks off within the lash
adjuster, replace the affected rocker arm.
CS
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