Chevrolet 70 Series 1970, Service Manual

Page: 50 / 841

CAB AND BODY MOUNTINGS 1-19
WIPER MOTOR TROUBLESHOOTING
A general in sp ection of w iper sy ste m should
p reced e any attem pt to rep air m otor. B e su re to
check air lin e for plugged fittin g s, kinked tubing
or leak s. Make su re that a ll connections a r e tight.
TROUBLESHOOTING AND REPAIR
MOTOR REPAIR
Key num bers in text r e fe r to figu re 24.
For a ll internal rep a irs it is n e c e ssa r y to r e ­
m ove head assem b ly V iew s A and C, figu re 24. If
n e c e ssa r y to take m otor apart, a ll p arts should be
carefully checked for w ear and lubricated b efore
a sse m b ly . Worn p arts should be replaced.
V alve Head R eplacem ent
1. Rem ove s ix valve head attaching sc r e w s
and turn shaft so that gear rack a ssem b ly, View B,
figu re 24, is brought back a s near a s p o ssib le to
the head.
2. Lift head and unhook valve stop unit a s s e m ­
b ly, View B .
3. To rep lace head, m ove gear rack a ssem b ly
View B, figure 24, a s near to the opening a s p o s­
s ib le .
4. R aise valve stop unit and hook under pin
View C, fig u re 24, m ik in g su r e that a ir p a ssa g e in
head is d irectly opposite a ir tube in cylin d er.
5. Move rack a ssem b ly sligh tly away from
end to provide c lea ra n ce fo r a ssem b lin g head.
NOTE: U se new gasket when replacing head.
6
. P la c e a sm a ll amount of g r e a se on a ll mov­
ing p a rts and head. R eplace head by r ev ersin g
p reced in g rem oval p ro ced u res.
P isto n P ackings R eplacem ent
1. R em ove head a s outlined p reviou sly.
2. R em ove top co v er, V iew A, figu re 24, by
rem oving four attaching s c r e w s.
NOTE: A quick method to check for leak s is to
disconnect the line , stop up one end and blow sm oke
through the other; th is w ill reveal the point of le a k ­
a ge, if any.
If air lin e is sa tisfa c to r y , turn on w iper r e g ­
ulating valve to diagnose m otor trouble a s follows:
IMPORTANT: B e su re cover position is m ark­
ed so that it can be repositioned exactly when a s ­
sem b lin g.
3. R em ove plate and bushing, then rem ove
shaft and gea r.
4. Gear rack can now be withdrawn from c y l­
inder.
5. D ism an tle a ssem b ly , replacing dam aged or
worn packings or other p a r ts.
6
. Clean a ll p a rts thoroughly, lubricating pack­
ings and cylin d er w all with a sp e c ia l form ula g r e a se
designed for th is purpose.
7. A ssem b le p a rts making su re they are placed
in th eir re la tiv e p o sitio n s a s shown in View B,
figure 24.
IMPORTANT: A shim must be used
to slip the gear rack assembly into the
cylinder as follows:
a. Wrap entire rack in steel shim as
shown in View D, figure 24.
b. Insert rack and shim into cylinder
far enough to pass opposite end of opening
(View D, fig. 24). Hold shlrn and push rack
down as far as it will gb. Hold rack at
this point with screwdriver and withdraw
shim.
c. Lubricate end of cylinder before
replacing head.
Shaft R eplacem ent
1. R em ove valve head a ssem b ly a s described
p rev io u sly .
CONDITION PROBABLE CAUSE
a. Wiper w orks slow ly or uneven.
b. Wiper runs slow ly and without pow er.
c. W iper runs with jerk s.
d. Wiper w orks only in one direction.
e. W iper w ill not run.
Shaft bind. Make su re that shaft i s free
and does not bind in the h ole.
Packing le a k s. D efective valve.
Bent valve stop unit.
Broken valve stop unit. V alves a r e bent
or stick y .
A ir lin e plugged. Valve d efective or
broken. Gear se c to r broken.
W iper valve or piston gum m ed up due to
foreign d ep osits, due to dirty a ir lin e.
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL