Engine Oil Pressure; Service Procedures; Valve Timing; Valve, Guide And Seal - Jeep cherokee 2000 Service Manual

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DIAGNOSIS AND TESTING (Continued)
filter runoff, and main bearing cap to cylinder
block mating surfaces.
(4) If no leaks are detected, pressurize the crank-
case as outlined in the, Inspection (Engine oil Leaks
in general)
CAUTION: Do not exceed 20.6 kPa (3 psi).
(5) If the leak is not detected, very slowly turn the
crankshaft and watch for leakage. If a leak is
detected between the crankshaft and seal while
slowly turning the crankshaft, it is possible the
crankshaft seal surface is damaged. The seal area on
the crankshaft could have minor nicks or scratches
that can be polished out with emery cloth.
CAUTION: Use extreme caution when crankshaft
polishing is necessary to remove minor nicks and
scratches. The crankshaft seal flange is especially
machined to complement the function of the rear oil
seal.
(6) For bubbles that remain steady with shaft
rotation, no further inspection can be done until dis-
assembled.

ENGINE OIL PRESSURE

(1) Disconnect connector and remove oil pressure
sending unit.
(2) Install Oil Pressure Line and Gauge Tool
C-3292 or equivalent. Start engine and record pres-
sure. Refer to Oil Pressure in Engine Specifications
for the correct pressures.

SERVICE PROCEDURES

VALVE TIMING

• Disconnect the spark plug wires and remove the
spark plugs.
• Remove the engine cylinder head cover.
• Remove the capscrews, bridge and pivot assem-
bly, and rocker arms from above the No.1 cylinder.
• Alternately loosen each capscrew, one turn at a
time, to avoid damaging the bridge.
• Rotate the crankshaft until the No.4 piston is at
top dead center (TDC) on the compression stroke.
• Rotate the crankshaft counterclockwise (viewed
from the front of the engine) 90°.
• Install a dial indicator on the end of the No.1
cylinder intake valve push rod. Use rubber tubing to
secure the indicator stem on the push rod.
• Set the dial indicator pointer at zero.
• Set the dial indicator pointer at zero.
• Rotate the crankshaft clockwise (viewed from
the front of the engine) until the dial indicator
pointer indicates 0.305 mm (0.012 inch) travel dis-
tance (lift).
• The timing notch index on the vibration damper
should be aligned with the TDC mark on the timing
degree scale.
• If the timing notch is more than 13 mm (1/2
inch) away from the TDC mark in either direction,
the valve timing is incorrect.
• If the valve timing is incorrect, the cause may be
a broken camshaft pin. It is not necessary to replace
the camshaft because of pin failure. A spring pin is
available for service replacement.

VALVE, GUIDE AND SEAL

Clean all carbon deposits from the combustion
chambers, valve ports, valve stems, valve stem
guides and head.
Clean all grime and gasket material from the
engine cylinder head machined gasket surface.
Inspect for cracks in the combustion chambers and
valve ports.
Inspect for cracks on the exhaust seat.
Inspect for cracks in the gasket surface at each
coolant passage.
Inspect valves for burned, cracked or warped
heads.
Inspect for scuffed or bent valve stems.
Replace valves displaying any damage.
VALVE REFACING
(1) Use a valve refacing machine to reface the
intake and exhaust valves to the specified angle.
(2) After refacing, a margin of at least 0.787 mm
(0.031 inch) must remain (Fig. 13). If the margin is
less than 0.787 mm (0.031 inch), the valve must be
replaced.
VALVE SEAT REFACING
(1) Install a pilot of the correct size in the valve
guide bore. Reface the valve seat to the specified
angle with a good dressing stone. Remove only
enough metal to provide a smooth finish.
(2) Use tapered stones to obtain the specified seat
width when required.
(3) Control valve seat runout to a maximum of
0.0635 mm (0.0025 in.)— (Fig. 14).
VALVE STEM OIL SEAL REPLACEMENT
Valve stem oil seals are installed on each valve
stem to prevent rocker arm lubricating oil from
entering the combustion chamber through the valve
guide bores. One seal is marked INT (intake valve)
and the other is marked EXH (exhaust valve).
Replace the oil seals whenever valve service is per-
formed or if the seals have deteriorated.
2.5L ENGINE 9 - 15