Pontiac FIREBIRD 1972 Service Manual page 257

3-6 1972 PONTIAC SERVICE MANUAL
,
TROUBLE DIAGNOSIS (Continued)
NOTE: Test procedures (6) and (c) require
vehicle to be on a hoist that supports wheels.
a. Bounce Test
NOTE: This is only a comparison type test to
help locate the suspected shock or noise condi-
tion before proceeding to Steps (6) and (c).
Test each front and rear shock by bouncing each
corner of the vehicle. This can usually be done by
lifting up and pushing down on the end of the bumper
near each corner of the vehicle until maximum move-
ment up and down is reached. Then let go of bumper
and observe if the up and down motion stops very
quickly. If up and down motion continues longer at
one corner when compared to opposite corner (exam-
ple, both front shocks), the one having the longer up
and down motion may be suspect. Do Not compare
front to rear. If complaint is noise, this test should
help to locate the suspected area.
b. lnspecting Shock Mountings
If noisy and/or loose shock mountings are suspected,
place vehicle on hoist that supports wheels and check
all mountings for the following conditions:
1.
Worn or defective grommets
2. Loose mounting nuts
3. Possible interference condition
4. Bump stops (rubber rebound bumpers) missing
If no apparent defects are noted in this step but noise
condition still exists when vehicle is bounced up and
down, proceed to test procedure C.
c. lnspecting Shocks for Leaks and Manually Operating
Shocks
This procedure is sub-divided into two general areas,
(1) Inspecting Shocks for Loss of Hydraulic Fluid
and (2) Manually Operating Shocks. It should aid to
localize defective shocks caused by internal noise in
the shock, weak, leaking, etc.
1. lnspecting Shocks for Possible Loss of Hydraulic
Fluid
(a) Disconnect each shock lower mounting as re-
quired and pull down on the shock until it is
fully extended.
(b) Inspect shocks for leaks in seal cover area.
Shock fluid is a very thin hydraulic fluid and
has a characteristic odor and dark brown tint.
See Fig. 3-1.
Certain precautions should be observed when
inspecting shocks for leaks:
-
Shocks may have glossy paint on them. Do
not confuse this paint with a leak condition.
-
A slight trace of shock fluid around the seal
cover area is not cause for replacement. The
shock seal is engineered to permit a very slight
seepage to lubricate the rod. The shock ab-
sorber has reserve fluid to compensate for the
slight seepage.
-
Shocks are sometimes incorrectly diagnosed
as leakers due to oil spray originating from
some other source. If in doubt, wipe the wet
area and manually operate shock as described
in Step (2). Fluid will reappear if shock is leak-
ing.
2. Manually Operating Shocks
NOTE: It may be necessary with certain types
of shock mountings to fabricate a bracket that
can be installed on a shock to enable a secure
gr~p of the shock when manually operating the
shock. See Fig. 3-2 for suggested methods of
providing a temporary grip.
This test should help to isolate the following
shock defects:
-
loose piston
-
binding condition internally
-
verify leaking shock
-
improper or defective valving
(a) If suspected problem is in front shocks, dis-
connect both front shock lower mountings
and stroke each shock as follows: Grip the
lower end of the shock securely and pull down
(rebound stroke) then push up (compression
ROD
EAL COVER AREA
AT TOP OF SHOCK
ABSORBER
RONT SHOCK ABSORBER
REAR SHOCK ABSORBER
Fig. 3-1 Seal Cover Area of Shock