Disassembly; Cleaning And Inspection - GMC T Series 1994 Repair Manual

Figure 18— Testing the Hydraulic Lifter
(Flat Type Only)

DISASSEMBLY

Disassemble
*
• Valves and components. Refer to the proper sec­
tion.
CLEANING AND INSPECTIO N
I Clean (Figures 19 and 20)
Tools Required:
J 8089 Wire Brush
J 8101 Valve Guide Cleaning Tool
Carbon from the com bustion chambers, using
J 8089 (figure 19).
Valve guides, using J 8101 (figure 20).
Valve stems and heads on a wire wheel.
Carbon and old gasket from the cylinder head gas­
ket surface.
Inspect
L *
• Cylinder head for cracks in the exhaust ports, com­
bustion chambers, or external cracks to the coolant
chamber. Gasket surfaces should be free of dam­
age.
• Valves for burning, pitting, or warpage. Grind or
replace as needed. Refer to " Valve Grinding."
Check the valve stems for scoring or excessive
wear. Stems must not be bent.
• Rocker arm studs (if used) for wear, damage, or
improper fit.
4. Operate the lifter through full travel of the plunger
by pumping the weight arm to fill the lifter with test
fluid and force out air.
5. Raise the weight arm to allow the plunger spring to
expand fully. Then lower the arm onto the ram and
commence turning the crank slowly (1 revolution
every 2 seconds).
6. Time indicator travel from the lower line (first line
above the set line) to the line marked 0.094 or 3/32
CYLINDER HEAD
• Valve seats for pitting or other damage. Grind or
• Rotators (if used). The rotators should rotate
Important
• Lifter must be completely submerged at all
times.
• Continue pumping for several strokes after defi­
nite resistance is felt.
inch, while rotating the cup with the crank. The
lifter is satisfactory if the rate is between 12 and 90
seconds.
reface as needed.
smoothly without binding.
(Typical)