Town Car V8-302 5.0L (1987)
Crankshaft Main Bearing: Customer Interest
Engine - Knocking Noise
Article No.
ENGINE - "KNOCKING" NOISE - 5.0L -
87-11-12
INCORRECT MAIN BEARING CLEARANCES
FORD:
1985-86 LTD
1985-87 MUSTANG, THUNDERBIRD, FORD
LINCOLN-MERCURY: 1985-86 CAPRI, MARQUIS
1985-87 COUGAR, MERCURY, MARK VII, CONTINENTAL, LINCOLN TOWN CAR
LIGHT TRUCK:
1985-87 E-SERIES, F-SERIES, BRONCO
This article is being republished in its entirety to advise dealership technicians that the number five (5) rear main bearing is not affected and does not
require service.
ISSUE:
A low end "knocking" noise right after cold and/or warm engine start-up may be caused by excessive main bearing clearances in one (1)
through four (4) of the five (5) main bearing journals. This condition may also be mildly present when the vehicle engine is under a no load
(float) condition. The "knocking" noise can be described as sounding like a few sharp "raps".
ACTION:
To correct this, use the following diagnostic and service procedure to determine if oversize bearings should be installed in main bearing
journals one (1) through four (4). Refer to the bearing usage chart below for service part applications.
1985-87 5.0L MAIN BEARING USAGE CHART
Name
Color Code
Part No.
Service No.
Main Bearing -
Blue
D20E-6A338-BA
C3AZ-6333-AB
Lower
Thrust Bearing -
Blue
D20E-6A339-BA
C3AZ-6337-AB
Lower
Main Bearing -
Green
C50E-6A338-C
C3AZ-6333-AC
Lower
Thrust Bearing -
Green
C50E-6A339-C
C3AZ-6337-AC
Lower
Main Bearing -
Green
C50E-6333-C
C3AZ-6333-S
Upper
Thrust Bearing -
Green
C50E-6337-C
C3AZ-6337-S
Upper
1.
Refer to the appropriate Shop Manual and Gasoline Engine Overhaul Manual for instruction in determining "knock" noise.
2.
In addition, using an open stethoscope, search around exhaust manifold joint, thermactor system components, etc. for pulsing air or exhaust leaks
that can be confused with "knocking" noise. Make sure that powertrain components and exhaust system components are not grounding out on body
or chassis parts.
3.
Using a contact stethoscope, locate source of "knock" (high or low, front or rear of engine, etc.). If "knock" seems to be low in engine, and is
present as a few sharp "raps" right after start-up but remains under no-load or "float" conditions, main bearing clearances are likely to be the cause.
4.
Remove oil pan as outlined in the appropriate Shop Manual, Section 21-21.
5.
Using a "plastigage" and following procedure in appropriate Shop Manual, Section 21-01, determine main bearing clearances in journal numbers
1, 2, 3 and 4 ONLY.
6.
If measured clearance is less than .002 at any journal, no action is required at journal. If measured clearance is greater than .002, but less than
.003, install a "blue" half shell in main bearing cap only. Refer to bearing usage chart for correct service part number.
NOTE:
It is not necessary to measure clearance and/or replace the number five (5) main bearing.
7.
If measured clearance is greater than .003, install a "green" half shell in main bearing cap only. Refer to bearing usage chart for correct service part
number.
