Mack ASET AC Service Manual Download

Page: 386 / 536

REPAIR INSTRUCTIONS, PART 2

Page 373

12. Remove the roller tappet from the EUP bore

by hand. Do not use a tool as it could
damage the bore. Place the roller tappet in a
clean area and cover it to prevent the entry
of dirt and other contaminants.

Tappet Guide Pin and Tappet Bore
Inspection

1. Visually inspect the EUP bore in the cylinder

block for protrusion of the guide pin into the
bore. If the pin protrudes approximately
0.080 inch (2 mm) into the bore and is not
damaged, it is OK and no further action is
required.

2. If the guide pin end is damaged or does not

protrude approximately 0.080 inch (2 mm)
into the bore, replace it as follows:

Using a 1/4-inch diameter punch from
outside of the cylinder block, drive the
guide pin from its bore.

Clean the pin bore in the block and a

new

pin, part No. 183GC252, with

Loctite

primer “T.” Then, coat the bore

and pin with Loctite

609, or

equivalent.

Drive the pin into the bore until it is
flush with the cylinder block outer
surface as shown in Figure 447.

Occasionally, a failure will result in severe wear
and breakage of the roller and roller axle, causing
these parts to separate from the lifter body.
Subsequently, the lifter legs (which had retained
the axle in the lifter body) are bent outward and
driven up into the lifter bore by the cam lobe. This
action damages the bottom 1/4 to 3/8 inch
(6.4–9.5 mm) of the bore, preventing installation
of a new lifter.

The damaged bore area must be cleaned up with
a file, stone or emery paper before the new lifter
can be installed. Use care when removing raised
metal so not to enlarge the bore diameter. Any
remaining nicks or scores will not inhibit proper
function of the parts and cause no problem.

A small amount of scuffing or foreign particle
scoring in a lifter bore can inhibit static-free
movement of a lifter. While this will not cause a
lifter to hang-up during engine operation, it is
sometimes noticed during lifter removal or
installation. If this condition is encountered, use a
brake hone to lightly finish the bottom area of the
lifter bore. Trial-fit the lifter until the high spots
have been removed and free-movement is
re-established.

If the EUP tappet bore is damaged due to a
tappet and tappet guide pin failure, the damaged
bore is usable as long as a new tappet cannot be
“rocked” from side-to-side in the bore.

If a new guide pin does not have the proper
interference fit in the guide bore, meaning the pin
fit in the bore is a slip-fit (pin and bore diameter is
the same) to 0.001inch (0.025 mm) loose, then
the pin will need to be retained with Loctite

If a new EUP tappet does not move freely in the
bore, clean the bore as described below.

Salvaging a Damaged EUP Tappet
Bore

Occasionally, severe failure of an EUP tappet
roller and axle will result in parts of the tappet
being driven up against the bottom of the tappet
bore, causing damage to the bottom of the bore.
This damage must be repaired. Depending upon
the extent of the damage, it may be necessary to
begin with a small die grinder to remove the
displaced material, removing only the high spots
to bring them down to the remaining bore surface,
then finishing with a fine file, stone or emery
paper. The bore and adjacent areas must be
thoroughly cleaned to remove all metal particles
and abrasive material. Perform a trial-fit of the
EUP tappet and check for freedom of movement
in the bore.

Mack ASET AC, Service Manual

Search results

Summary of Contents for ASET AC

Reviews:

Related manuals for ASET AC

Brands by name

Popular brands