Chevrolet 1977 Monte Carlo, Repair Manual

Page: 143 / 428

BRAKES 5-7
BENDIX T A N D E M POW ER BRAKE UNIT
UNIT REPAIR
Disassembly
1. Scribe a line across the front and rear housings to
facilitate reassembly.
2. Carefully rem ove hydraulic push rod and seal and
slide seal from rod.
3. R em ove vacuum check valve and grom m et.
4. R em ove dust boot and silencer from operating valve
rod.
5. R em ove dust guard retainer, dust guard and
silencers from rear plate hub w ith an awl. Then reinstall
steel retainer on hub.
6. Squirt denatured alcohol down the operating valve
rod to lubricate rubber grom m et in the valve plunger.
7. Position two sm all blocks o f w ood on either side o f
air valve rod and install end o f air valve rod in vise, leaving
just enough clearance to position tw o (2) open end wrenches
between the vise and retainer on hub o f rear plate.
8. U sin g the wrench nearest the vise as a pry, force the
air valve off the ball end o f the rod. D O N O T dam age the
plastic hub or allow vacuum cylinder to fall to the floor (fig.
5 -IB and 5-2B).
9. The edge o f the rear housing contains tw elve (12)
lances. Four (4) o f these lances (one in each quadrant) are
deeper than the other lances. The m etal that forms the four
(4) deep lances must be partially straightened so that the
lances w ill clear the cutouts in the front housing. If the m etal
tabs that form the deep lances break during straightening,
the housing must be replaced (fig. 5-3B).
10. R em ove the hydraulic push rod and vacuum seal
from the front housing.
11. A ttach base o f H olding Fixture J-22805 to front
housing w ith nuts and washers and draw down tight to
elim inate bending or dam age to studs.
12. Place power unit with H olding Fixture J-22805 in
an arbor press with rear housing up and secure to plate o f
press by a suitable m eans o f holding T ool J-22805 (fig. 5-
4B). By using a 1-1/2" open end wrench on Tool J-22805
and allow ing unit to turn against back o f arbor press, press
will hold unit from turning.
13. Place Spanner W rench J-9504 over studs on rear
shell (fig. 5-4B). U se three washers and nuts to attach
w rench to housing. U se a suitable piece o f pipe o f
approxim ately tw o inches I.D . and approxim ately three
inches in length. Place over plastic diaphragm plate hub.
Place a piece o f flat stock steel over end o f pipe and press
rear housing down far enough to relieve tension o f
diaphragm rubber lip and spring.
14. R otate spanner bar counterclockw ise until the
lances in the edge o f the rear housing are aligned with the
cut-outs in the front housing. Considerable effort may be
required to rotate the front housing.
C A U T IO N : T h e diap h rag m retu rn spring
is com pressed in th e p ow er section and
expands as th e pressure on th e housings
is rem oved. If th e housings do not
s ep arate w h e n th e s crew has been turn ed
s lig h tly to reduce th e pressure, ta p th e
housings w ith a rubber h a m m e r to break
th e bond.
15. Slow ly release press to permit the two housings to
separate.
16. C ontinue to release press until diaphragm spring
tension has been rem oved.
N— SI LENCER RET A I NE R
V A L V E OPERATI NG ROD
Fig. 5-1 B--Removing A ir Valve Rod Fig. 5-2 B ~A ir Valve Rod A ssem bly
O V E R H A U L M A N U A L