Chevrolet 70 Series 1970, Service Manual

Page: 269 / 841

REAR SUSPENSION 4-56
MOUNT CONTROL "*
VALVE LEVEL ! -
Figure 9—Dial Indicator Properly Installed
6. If bubbles appear at the exhaust p o rt (fig. 8),
it is an indication the exhaust valve assem bly is
defective and m ust be replaced.
7. If bubbles appear around edge of valve cover
p la te , the cover plate gasket m ust be rep laced .
8. If no leaks a r e detected, rem ove valve a s ­
sem bly fro m w ater, then with a i r p re s s u r e s till
connected to bellows p o rt, actuate o v e rtra v e l lev er
to expel any w ater which may have en tered exhaust
valve cham ber. Remove a i r line and connect it to
a i r inlet p o rt and re p eat operation to rem ove w ater
fro m a ir inlet valve cham ber.
HEIGHT CONTROL VALVE
ADJUSTMENTS
To p ro p e rly adjust the height control valve,
it is ESSENTIAL that the following p ro c e d u re s be
followed and in the sequence mentioned:
T h ree m ain adjustm ents a r e req u ired .
NOTE: The height control valve assem bly m ust
be rem oved from vehicle to p erfo rm the following
adjustm ents:
1. O v e rtrav e l le v e r cen ter position adjustm ent
2. A ir intake and exhaust valve le v e r gap ad­
ju stm en ts.
3. T im e delay check.
IMPORTANT: The silicone fluid should be
drain ed from valve assem bly before p erform in g
the f ir s t two adjustm ents m entioned prev io u sly .
NOTE: The following tools shouldbe used when
p erfo rm in g valve adjustm ents:
REQUIRED TOOLS
Tool Tool Num ber
Valve C ore R e p l a c e r ..................................... J-6888
O v e rtra v e l L e v e r P isto n C o m p re sso r . . . J-8424
Allen W renches (Sizes 3 /32-inch
and 1 / 8 - i n c h ) .......................... P ro c u re locally
Stop W a tc h ........................................ P ro c u re locally
Dial Ind icator Set (Having m inim um
rang e of 0.020 i n c h ) ................. P ro c u re locally
A ir Line Fitting A ssem bly C o n sists of:
(1) 2-Inch length of % H-9 hose . . P ro c u re locally
(1) W eatherhead pipe fitting ............... 00904-104
(1) W eatherhead in v e rte d fitting . . . . 00904-B04
Vacuum Line F it t i n g ................. Sun T e s te r #115-3
Depth Gauge and Straightedge . . P ro c u re locally
Conventional Type Eye D ropper . P ro c u re locally
OVERTRAVEL LEVER CENTER
POSITION ADJUSTMENT
1. Clean e x te rio r of control valve assem bly.
2. Rem ove delay p isto n snap ring re ta in e r,
cover, and O -rin g fro m control valve assem bly,
then d rain off the silicone fluid.
3. Rem ove exhaust fitting and exhaust screen
fro m valve.
4. R e fe rrin g to figu re 9, s c rib e a line 1 -3 /8 -
inch fro m plug end of o v e rtra v e l le v e r control body.
5. P la ce valve assem b ly in v ise as shown in
fig u re 9.
6. If vacuum so u rc e is availab le, attach sup­
ply hose to valve exhaust p o rt (fig. 8) using Sun
T e s te r fitting #115-3 o r equivalent. Do not apply
vacuum a t th is tim e.
7. A ttach a i r p re s s u r e supply hose to a i r inlet
p o rt (fig. 8). Do not apply p r e s s u r e a t th is tim e .
8. Locate dial ind icator in po sitio n a s shown
in fig u re 9. Move o v e rtra v e l le v e r to full a i r ex­
haust position - TOP OF DELAY PISTON FLUSH
WITH TOP OF BORE - without o v ertrav elin g (posi­
tion "C ," fig. 10). R elocate ind icato r push rod to
ju st contact 1 -3 /8 -in c h m ark on control body and
re s e t in d icato r dial to zero (0) at th is point (posi­
tion "C ," fig. 10).
9. Move o v e rtra v e l le v e r to full a i r intake
position without o v ertrav elin g (position "A ," fig.
10) (delay piston at bottom of bo re). Take indicator
read ing which may v ary fro m 0.160" to 0.190".
10. R epeat step s 8 and 9 above to rech eck th is
reading.
11. Divide the to tal tra v e l dim ension by two
(exam ple: 0.170" - 2 - 0.085"), then move o v e r­
tra v e l le v e r back th is amount (0.085") to the cen ter
(position "B ," fig. 10).
IMPORTANT: Without disturbing le v e r cen ter
position, r e s e t indicator dial to z e ro (0), which
actually is 0.100” on in d icato r of type re g iste rin g
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL