Chrysler RAM TRUCK 2500 1994 Service Manual page 800

inder head to the bottom surface of spring retainer. I f
spacers are installed, measure from the top of spacer.
I f height is greater than 42.86 mm (1-11/16 inches),
install a 1.587 mm (1/16 inch) spacer i n head coun-
terbore. This should bring spring height back to nor­
mal 41.27 to 42.86 mm (1-5/8 to 1-11/16 inch).
VALVE STEM SHIELD / SPRING REPLACEMENT
This procedure is done with the cylinder head i n ­
stalled.
(1) Set engine basic timing to Top Dead Center
(TDC) and remove air cleaner.
(2) Remove cylinder head covers and spark plugs.
(3) Remove coil wire from distributor and secure to
good ground to prevent engine from starting.
(4) Using suitable socket and flex handle at crank­
shaft retaining bolt, turn engine so the N o . l piston is
at TDC on the compression stroke.
(5) Remove rocker arms.
(6) With air hose attached to an adapter installed
in N o . l spark plug hole, apply 620-689 kPa (90-100
psi) air pressure.
(7) Using Valve Spring Compressor Tool
MD-$98772A, compress valve spring and remove re­
tainer valve locks and valve spring.
(8) Install seals on the exhaust valve stem and po­
sition down against valve guides.
(9) The intake valve stem seals should be pushed
firmly and squarely over the valve guide using the
valve stem as a guide. DO NOT force seal against top
of guide. When installing the valve retainer locks,
compress the spring only enough to install the locks.
(10) Follow the same procedure on the remaining 7
cylinders using the firing sequence 1-8-4-3-6-5-7-2.
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 covers and coil wire to distributor.
(14) Install air cleaner.
(15) Road test vehicle.
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 conditions 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.
T A P P E T 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. I f 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.