Hydraulic Lash Adjuster (Tappet) Noise Diagnosis; Hydrostatic Locked Engine; Connecting Rod Bearing Clearance; Repair Of Damaged Or Worn Threads - DaimlerChrysler LH New Yorker 1994 Electronic Service Manual

9 - 4 ENGINE
amount of taper present. Record all readings taken.
Refer to Engine Specifications. Plastigage gener-
ally is accompanied by two scales. One scale is
in inches, the other is a metric scale.
(5) Plastigage is available in a variety of clearance
ranges. The 0.025-0.076 mm (.001-.003 inch.) is usu-
ally the most appropriate for checking engine bear-
ing proper specifications.

CONNECTING ROD BEARING CLEARANCE

Engine crankshaft bearing clearances can be de-
termined by use of Plastigage or equivalent. The
following is the recommended procedure for the use
of Plastigage:
(1) Rotate the crankshaft until the connecting rod
to be checked is at the bottom of its stroke.
(2) Remove oil film from surface to be checked.
Plastigage is soluble in oil.
(3) Place a piece of Plastigage across the entire
width of the bearing shell in the bearing cap approxi-
mately 6.35 mm (1/4 inch.) off center and away from
the oil hole (Fig. 2). In addition, suspect areas can be
checked by placing plastigage in the suspect area.
(4) Before assembling the rod cap with Plastigage
in place, the crankshaft must be rotated until the
connecting being checked starts moving toward the
top of the engine. Only then should the cap be as-
sembled and torqued to specifications. Do not ro-
tate the crankshaft while assembling the cap
or the Plastigage may be smeared, giving inac-
curate results.
(5) Remove the bearing cap and compare the
width of the flattened Plastigage (Fig. 3) with the
metric scale provided on the package. Locate the
band closest to the same width. This band shows the
amount of clearance in thousandths of a millimeter.
Differences in readings between the ends indicate
the amount of taper present. Record all readings
taken. Refer to Engine Specifications. Plastigage
generally is accompanied by two scales. One
scale is in inches, the other is a metric scale.
(6) Plastigage is available in a variety of clearance
ranges. The 0.025-0.076 mm (.001-.003 inch.) is usu-
ally the most appropriate for checking engine bear-
ing proper specifications.
HYDRAULIC LASH ADJUSTER (TAPPET) NOISE
DIAGNOSIS
A tappet-like noise may be produced from several
items. Check the following items.
(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 cylin-
der head. Low speed running up to 1 hour may be
required.
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) Low oil pressure.
(4) The oil restrictor plate in the head gasket
plugged with debris.
(5) Air ingested into oil due to broken or cracked
oil pump pick up.
(6) Worn valve guides.
(7) Rocker arm loose, adjuster stuck or at maxi-
mum extension and still leaves lash in the system.
(8) Faulty hydraulic lash adjuster.
(a) Check for sponginess while still installed in
the engine. With the cam follower on the base
circle of camshaft, depress part of rocker arm just
over adjuster. Normal adjusters should feel very
firm. Spongy adjusters can be depressed to the
bottomed position easily. If lash adjusters are
spongy repeat step (2). If sponginess remains re-
place rocker arm/lash adjuster assembly.
(b) Remove suspected rocker arm/lash adjuster
assembly and replace the assembly.
Do not disassemble the lash adjuster from
the rocker arm.

REPAIR OF DAMAGED OR WORN THREADS

Damaged or worn threads (including aluminum
head spark plug threads) can be repaired. Essen-
tially, this repair consists of drilling out worn or
damaged threads, tapping the hole with a special
Heli-Coil (or equivalent) Tap, and installing an in-
sert into the tapped hole. This brings the hole back
to its original thread size.
CAUTION: Be sure that the tapped holes maintain
the original centerline.
Heli-Coil tools and inserts are readily available
from automotive parts jobbers.

HYDROSTATIC LOCKED ENGINE

When an engine is suspected to be hydrostatically
locked, regardless of what caused the problem, these
steps should be used.
CAUTION: Do Not Use Starter Motor To Rotate En-
gine, severe damage may occur.
(1) Inspect air cleaner, induction system and in-
take manifold to insure system is dry and clear of
foreign material.
(2) Remove negative battery cable.
(3) Place a shop towel around the spark plugs
when removing them from the engine. This will
catch any fluid that may possibly be in the cylinder
under pressure.