Intake Manifold Leakage Diagnosis - Jeep cherokee 2000 Service Manual

9 - 72 4.0L ENGINE
DIAGNOSIS AND TESTING (Continued)
CONDITION
LOW OIL PRESSURE
OIL LEAKS
EXCESSIVE OIL CONSUMPTION
OR SPARK PLUGS OIL FOULED

INTAKE MANIFOLD LEAKAGE DIAGNOSIS

An intake manifold air leak is characterized by
lower than normal manifold vacuum. Also, one or
more cylinders may not be functioning.
POSSIBLE CAUSES
1. Low oil level
2. Faulty oil pressure sending unit
3. Clogged oil filter
4. Worn oil pump
5. Thin or diluted oil
6. Excessive bearing clearance
7. Oil pump relief valve stuck
8. Oil pump suction tube loose,
broken, bent or clogged
9. Oil pump cover warped or
cracked
1. Misaligned or deteriorated
gaskets
2. Loose fastener, broken or porous
metal part
3. Front or rear crankshaft oil seal
leaking
4. Leaking oil gallery plug or cup
plug
1. PCV System malfunction
2. Defective valve stem seal(s)
3. Worn or broken piston rings
4. Scuffed pistons/cylinder walls
5. Carbon in oil control ring groove
6. Worn valve guides
7. Piston rings fitted too tightly in
grooves
WARNING: USE EXTREME CAUTION WHEN THE
ENGINE IS OPERATING. DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR
HANDS NEAR THE PULLEYS, BELTS OR THE FAN.
DO NOT WEAR LOOSE CLOTHING.
CORRECTION
1. Check oil level and fill if
necessary
2. Install new sending unit
3. Install new oil filter
4. Replace worn gears or oil pump
assy
5. Change oil to correct viscosity.
Refer to this group for correct
procedure/engine oil specifications
6. Measure bearings for correct
clearance
7. Remove valve to inspect, clean
and reinstall
8. Inspect suction tube and clean or
replace if necessary
9. Install new oil pump
1. Replace gasket
2. Tighten, repair or replace the part
3. Replace seal
4. Remove and reseal threaded
plug. Replace cup style plug
1. Refer to group 25, Emission
Control System for correct operation
2. Repair or replace seal(s)
3. Hone cylinder bores. Install new
rings
4. Hone cylinder bores and replace
pistons as required
5. Remove rings and de-carbon
piston
6. Inspect/replace valve guides as
necessary
7. Remove rings and check ring end
gap and side clearance. Replace if
necessary
XJ