Chrysler RAM TRUCK 2500 1994 Service Manual page 828

(7) Using Valve Spring Compressor Tool
MD-998772A with adapter 6716A, compress valve
spring and remove retainer valve locks and valve
spring.
(8) Install seals on the exhaust valve stem and po­
sition down against valve guides. The exhaust valve
stem seal is brown.
(9) The black intake valve stem seals should be
pushed firmly and squarely over the valve guide us­
ing the valve stem as a guide. DO NOT force seal
against top of guide. When installing the valve re­
tainer locks, compress the spring only enough to in­
stall the locks.
(10) Follow the same procedure on the remaining 7
cylinders using the firing sequence 1-10-9-4-3-6-5-8-
7-2. Make sure piston i n cylinder is at TDC on the
valve spring that is being removed.
(11) Remove adapter from the N o . l spark plug
hole.
(12) Install rocker arms.
(13) Install air cleaner.
(14) Connect the negative cable to the battery.
(15) Road test vehicle and check for leaks.
HYDRAULIC TAPPETS
Before disassembling any part of the engine to cor­
rect tappet noise, check the oil pressure. I f vehicle
has no oil pressure gauge, install a reliable gauge at
the pressure sending unit. The pressure should be
between 207-552 kPa (30-80 psi) at 3,000 RPM.
Check the oil level after the engine reaches normal
operating temperature. Allow 5 minutes to stabilize
oil level, check dipstick. The oil level i n the pan
should never be above the FULL mark or below the
ADD OIL mark on dipstick. Either of these 2 condi­
tions could be responsible for noisy tappets.
OIL LEVEL
HIGH
I f oil level is above the FULL mark, i t is possible
for the connecting rods to dip into the oil. With the
engine running this condition could create foam i n
the oil pan. Foam i n oil pan would be fed to the hy­
draulic tappets by the oil pump causing them to lose
length and allow valves to seat noisily.
LOW
Low oil level may allow oil pump to take i n air.
When air is fed to the tappets, causes them to lose
length and allows valves to seat noisily. Any leaks on
intake side of oil pump through which air can be
drawn will create the same tappet action. When tap­
pet noise is due to aeration, i t may be intermittent or
constant, and usually more than 1 tappet will be
noisy. When oil level and leaks have been corrected,
engine should be operated at fast idle for sufficient
time. This allows all of the air inside of the tappets
to be bled out.
TAPPET NOISE DIAGNOSIS
(1) To 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.
Worn valve guides or cocked springs are
sometimes mistaken for noisy tappets. I f such is
the case, noise may be dampened by applying
side thrust on the valve spring. If noise is not
appreciably reduced, it can be assumed the
noise is i n the tappet. Inspect the rocker arm
push rod sockets and push 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) Disconnect the negative cable from the battery.
(2) Remove the air cleaner.
(3) Remove cylinder head cover.
(4) Remove rocker arm assembly and push rods.
Identify push rods to ensure installation i n original
location.
(5) Remove intake manifold.
(6) Remove the cylinder head i f the end tappets
are to be removed.
(7) Remove yoke retainer spider and tappet align­
ing yokes (Fig. 1).
(8) 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.
(9) 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.
(10) Check camshaft lobes for abnormal wear.