Mack ASET AC, Service Manual

Page: 247 / 536

Page 234
REPAIR INSTRUCTIONS, PART 1
Valve Stem Seals
The current design valve seal can be identified by
the fact that it fits on the top of the valve guide.
This seal, and the top of the valve guide are
approximately 1/8 inch (6.35 mm) smaller than
the previous seal and guide to allow clearance
with the inner valve spring at exhaust locations.
For standardization, the new valve guide and seal
are used at the inlet locations as well as the
exhaust locations, with either single springs or
dual valve springs.
248
Figure 248 — Valve Stem Seal (Current Design)
Approximately the first 200 ASET™ engines used
a seal and guide arrangement which if servicing
is required, both the guide and the seal must be
replaced/updated to the current configuration
parts. For detailed instructions, refer to Service
Bulletin SB-213-017.
Cylinder Head Cleaning and
Inspection
Cleaning the cylinder head is important. While
cleaning the cylinder head, carefully inspect the
areas around the cup plugs and the coolant
jacket. If the cup or pipe plugs show signs of
leaking, they should be replaced. The cylinder
head should also be inspected for cracks or other
possible defects that may be reason for
replacement. If damage is not found until after the
engine is assembled, the cylinder head must be
removed, disassembled and rebuilt again.
SOLVENT TANK CLEANING
Cleaning solvent is flammable and toxic to the
eyes, skin and respiratory tract. Skin and eye
protection is required. Avoid repeated or
prolonged contact. Use only in a
well-ventilated area.
Compressed air used for cleaning can create
airborne particles that may enter the eyes or
irritate the skin. Pressure must not exceed 30
psi (207 kPa). Eye protection is required. Use
only with effective chip guarding and
personal protective equipment
(goggles/shield, gloves, etc.).
1. Fill the tank with a suitable solvent and
immerse the parts in the solution to loosen
any dirt and debris.
2. Scrape any remaining gasket material from
the cylinder head.
3. Using a wire brush or rotary wheel, remove
any rust, corrosion or other debris from the
head.
4. Rinse the cylinder head, making sure that all
surfaces are clean and free of debris.
5. Using due care and caution, dry the head
with compressed air.
1. Steel Retainer Band
2. Multi-Lip Section
3. Primary Lip 4. Valve Guide
5. Three Sharp Edges
5-111.bk Page 234 Monday, July 10, 2006 2:26 PM