Chrysler RAM TRUCK 2500 1994 Service Manual page 747

TAPPET NOISE DIAGNOSIS
(1) Tb determine source of tappet noise, operate en­
gine at idle with cylinder head covers removed.
(2) Feel each valve spring or rocker arm to detect
noisy tappet. The noisy tappet will cause the affected
spring and/or rocker arm to vibrate or feel rough i n
operation.
W o r n valve guides o r c o c k e d s p r i n g s a r e
sometimes mistaken for noisy tappets. I f such is
the c a s e , n o i s e m a y b e d a m p e n e d b y a p p l y i n g
side thrust o n t h e valve s p r i n g . I f noise i s n o t
appreciably r e d u c e d , i t can b e assumed the
n o i s e is i n the tappet. I n s p e c t the r o c k e r arm
push rod sockets a n d p u s h rod ends for wear.
(3) Valve tappet noise ranges from light noise to a
heavy click. A light noise is usually caused by exces­
sive leak down around the unit plunger or by the
plunger partially sticking i n the tappet body cylinder.
The tappet should be replaced. A heavy click is
caused by a tappet check valve not seating or by for­
eign particles becoming wedged between the plunger
and the tappet body. This will cause the plunger to
stick i n the down position. This heavy click will be
accompanied by excessive clearance between the
valve stem and rocker arm as valve closes. I n either
case, tappet assembly should be removed for inspec­
tion and cleaning.
The valve train generates a noise very much like a
light tappet noise during normal operation. Care
must be taken to ensure that tappets are making the
noise. I n general, i f more than one tappet seems to
be noisy, its probably not the tappets.
REMOVAL
(1) Remove the air cleaner.
(2) Remove cylinder head cover.
(3) Remove rocker assembly and push rods. Iden­
tify push rods to ensure installation i n original loca­
tion.
(4) Remove intake manifold.
(5) Remove yoke retainer and aligning yokes.
(6) Slide Hydraulic Tappet Remover/Installer Tool
C-4129-A through opening i n cylinder head and seat
tool firmly i n the head of tappet.
(7) Pull tappet out of bore with a twisting motion.
I f all tappets are to be removed, identify tappets to
ensure installation i n original location.
(8) I f the tappet or bore i n cylinder block is scored,
scuffed, or shows signs of sticking, ream the bore to
next oversize. Replace with oversize tappet.
CAUTION: T h e plunger and tappet bodies are not
interchangeable. T h e plunger and valve must al­
ways be fitted to the original body. It is advisable to
work on one tappet at a time to avoid mixing of
parts. Mixed parts are not compatible. DO NOT dis­
assemble a tappet on a dirty work bench.
INSTALLATION
(1) Lubricate tappets.
(2) Install tappets and push rods i n their original
positions. Ensure that the oil feed hole i n the side of
the tappet body faces up (away from the crankshaft).
(3) Install aligning yokes with ARROW toward
camshaft.
(4) Install yoke retainer. Tighten the bolts to 23
N-m (200 in. lbs.) torque. Install intake manifold.
(5) Install push rods i n original positions.
(6) Install rocker arms.
(7) Install cylinder head cover.
(8) Start and operate engine. Warm up to normal
operating temperature.
CAUTION: To prevent damage to valve mechanism,
engine must not be run above fast idle until all hy­
draulic tappets have filled with oil and have become
quiet.
W A I V E TIMING
(1) Turn crankshaft until the No.6 exhaust valve is
closing and No.6 intake valve is opening.
(2) Insert a 6.350 mm (1/4 inch) spacer between
rocker arm pad and stem tip of No.l intake valve. A l ­
low spring load to bleed tappet down giving i n effect
a solid tappet.
(3) Install a dial indicator so plunger contacts
valve spring retainer as nearly perpendicular as pos­
sible. Zero the indicator.
(4) Rotate the crankshaft clockwise (normal run­
ning direction) until the valve has lifted 0.254 mm
(0.010 inch). The timing of the crankshaft should
now read from 10° before top dead center to 2° after
top dead center. Remove spacer.
CAUTION: DO NOT turn crankshaft any further
clockwise a s valve spring might bottom and result
in serious damage.
(5) I f reading is not within specified limits:
(a) Check sprocket index marks.
(b) Inspect timing chain for wear.
(c) Check accuracy of DC mark on timing indica­
tor.
VIBRATION DAMPER
REMOVAL
(1) Disconnect the negative cable from the battery.
(2) Remove fan shroud retainer bolts and set
shroud back over engine.
(3) Remove the cooling system fan.
(4) Remove the serpentine belt (refer to Group 7,
Cooling System).
(5) Remove the vibration damper pulley.