03-Q0-26
Engine-Service
03-oo-26
SERVICE PROCEDURES (Continued)
Piston Pin Diameter
Use a micrometer to inspect the piston pin diameter in
the
X
and
Y
directions at points A, B, C and D as
shown.
MICROMETER
A24230-A
Replace piston pin that is not within specifications. For
Specifications, refer to Section 03-Q 1 A (3.8L} or
Section 03-0 18 (4.6L}.
Connecting Rods
Piston
Pin Clearance-4.6L Engine
The interference between the connecting rod and the
piston pin (6135} should be within 0.0 1 5-Q.040 mm
(0.0006-0.00 16 inch}.
Cleaning
CAUTION: Do not use a caustic cleaning solution
or damage to connecting rods (6200) may occur.
Remove the connecting rod bearings (62 1 1} from the
connecting rods and caps. Identify each connecting
rod bearing location if connecting rod bearings are to
be reused. Clean the connecting rod in solvent,
including the rod bore and the back of the connecting
rod bearings. Blow out all passages with compressed
air.
Inspection
CAUTION: It is not necessary to ream or hone the
pin bore in the connecting rod. Replace damaged
connecting rod nuts and bolts or engine damage
may occur.
Inspect the connecting rods for signs of fractures and
the bearing bores for out-of-round and taper. If the
bore exceeds the recommended limits and
I
or if the
connecting rod is fractured, replace it. Check the ID of
the connecting rod piston pin bore. If the pin bore in the
connecting rod is larger than specification, install a
0.025 mm (0.001 inch} oversize piston pin. Prefit the
oversize piston pin to the piston pin bore by reaming or
honing the piston (6 1 08} to provide 0.007-0.0 13 mm
(0.0003-0.0005 inch} clearance (light slip fit}.
Assemble the piston, piston pin and connecting rod as
described.
The connecting rod and related parts should be
carefully inspected and checked so they conform to
specifications. For Specifications, refer to Section
03-Q 1 A (3.8L} or Section 03-0 1 8 (4.6L}. Various
forms of engine wear caused by these parts can be
readily identified.
A shiny surface on either pin boss inside of the piston
usually indicates that a connecting rod is bent.
Abnormal connecting rod bearing wear can be caused
by either a bent, worn or damaged crankpin or a
tapered connecting rod bore.
Twisted connecting rods can create an identifiable
piston skirt wear pattern, but badly twisted connecting
rods will disturb the action of the entire piston, piston
rings and may also cause excessive oil consumption.
Connecting
Rod Bending Clearance
Check the connecting rods for bend or twist on a
suitable alignment fixture. Follow the instructions of
the fixture manufacturer. If the bend and twist exceeds
specification, the connecting rod must be replaced.
Camshaft/Cylinder Head Journals
Cleaning
Clean the camshaft (6250} in solvent and wipe it dry.
Remove light scuffs, scores or nicks from the
camshaft-machined surfaces with a smooth oil stone.
On 3.8L engines, the camshaft must be replaced if
camshaft journals are excessively worn or scored.
Camshaft journals can be refinished to accommodate
0.38 mm (0.0 1 5 inch} undersize camshaft bearings
(626 1 }.
If
the journals do not ''clean up,' ' replace the
camshaft.
Inspection
Check camshaft bores for size, taper, roundness,
alignment and finish. If any of these exceed the limits
given in Specifications, install new camshaft bearings,
rebore cylinder head (6049} to accept oversize
camshaft or replace cylinder head.
1 997 Thunderbird, Cougar July 1996
Содержание Thunderbird
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