Chevrolet 1980 Light Duty Truck Repair Manual page 139

straight out. A considerable force will be required.
14. R em oval o f the air valve push rod assembly w ill
disassembly the control valve retainer.
15. R em ove the "O" ring from the air valve.
16. A ir valve push rod assemblies with a formed eye
on the end o f the push rod w ill be serviced using a com plete
assembly, since the floating control valve cannot be removed
over the eye end of the push rod.
C leaning
A fter disassembly, im m erse
denatured alcohol. Plastic parts, as well as the rubber power
diaphragms, should be cleaned in denatured alcohol or clean
brake fluid. Care should be taken to avoid chipping or
dam aging plastic parts in handling. U se air to blow out dirt
and cleaning solvent from recesses and internal passages.
Inspection of Rubber P arts
W ipe fluid from the rubber parts and carefully inspect
each rubber part for cuts, nicks or other damage. These
parts are the key to the control o f fluid or air flow. If there
is any question as to the serviceability o f rubber parts,
R E P L A C E them.
Inspecting M e ta l Parts
B A D L Y D A M A G E D ITEM S, OR TH O SE W H IC H
W O U L D T A K E E X T E N SIV E W O R K O R T IM E TO
R E P A IR , S H O U L D BE R E P L A C E D . In case o f doubt,
install new parts.
A ssem bly
Be careful during the rebuild procedure that no grease
or mineral oil com es in contact w ith the rubber parts o f the
power brake unit.
Lubricate power unit parts, as outlined below, with
power brake silicone lubricant. This lubricant is provided
in the service repair kit.
Front Housing Group Assembly.
1. Insert the N E W grom m et in the front housing.
2. Install the N E W vacuum check valve into the
grommet.
Power Piston Group (Fig. 5-2A)
1. Lubricate the "O" ring seal w ith silicone lubricant
and place on the air valve.
2. W ipe a thin film o f silicone lubricant on the large
and sm all O .D . o f the floaing control valve.
3. If the floating control valve needs replacement,
replace the com plete air valve push rod assembly.
4. Place the air valve end o f the air valve push rod
assembly into the tube o f the power piston. M anually press
the air valve push rod assembly so that the floating control
valve bottom s on the tube section o f the power piston.
5. Place lip o f retainer on the O .D . o f Tool J-23175 (fig.
5-3A). M anually press the retainer until seated in the power
piston tube (fig. 5-4A).
6. Install filter elem ent over the push rod eye and press
into the power piston tube.
7. U sing snap ring pliers, place the snap ring into the
groove in the air valve.
8. Install the rubber reaction bumper on the end o f the
air valve.
all metal parts in
diameter up.
o f the rubber reaction disc.
reaction body.
F ig . 5 - 3 A - - ln s t a ll in g A ir V a lv e P u s h R o d R e t a in e r
9. Install air valve spring on end o f air valve.
10. Install reaction body with large I.D . hole up.
11. Install reaction body retainer.
12. Install reaction piston into reaction body, large
13. A pply a light film o f silicone lubricant to the O .D .
14. Place the rubber reaction disc in the cavity o f the
F ig . 5 - 4 A ~ S e a t in g A ir V a lv e P u s h R o d R e t a in e r U s in g
J -2 3 1 7 5
BRAKES 5-3
O V E R H A U L M A N U A L