Subaru 2009 IMPREZA Service Manual page 2182

12.General Diagnostic Table
A: INSPECTION
1. CLUTCH
Symptom
1. Clutch slippage.
It is hard to perceive clutch slippage in
the early stage, but pay attention to the
following symptoms.
• Engine speeds up when shifting.
• High-speed driving is not possible;
especially rapid acceleration is not possi-
ble and vehicle speed does not increase
in proportion to the increase in engine
speed.
• Power drops particularly when ascend-
ing a slope, and there is a burning smell
of the clutch plate.
• Method of testing: Park the vehicle and
fully apply the parking brake. Disengage
the clutch and shift the transmission gear
into the 1st. Gradually increase the
engine speed while gradually allowing the
clutch to engage. The clutch function is
satisfactory if the engine stalls. However,
the clutch is slipping if the vehicle does
not move forward and the engine does
not stall.
2. Clutch drags.
As a symptom of this trouble, a harsh
scratching noise occurs and control
becomes difficult when shifting gears.
The symptom becomes more apparent
when shifting into the 1st gear. However,
because most trouble of this sort is due to
a defective synchronization mechanism,
perform the following tests.
• Method of testing:<Ref. to CL-30,
DIAGNOSTIC DIAGRAM OF CLUTCH
DRAG, INSPECTION, General Diagnos-
tic Table.>
The problem is caused by insufficient dis-
engagement of the clutch if an abnormal
noise occurs during this test.
3. Clutch chatters.
Clutch chattering is an unpleasant vibra-
tion to the whole vehicle when the vehicle
is just started with clutch partially
engaged.
General Diagnostic Table
Possible cause
(a) Oil on the clutch face
(b) Worn clutch face
(c) Deteriorated diaphragm spring
(d) Warped pressure plate or flywheel
(e) Defective release bearing holder
(a) Worn or rusty clutch disc hub spline
(b) Excessive deflection of clutch disc
face
(c) Crankshaft pilot needle bearing stick-
ing
(d) Cracked clutch disc face
(e) Stuck clutch disc (smeared by oil or
water)
(a) Adhesion of oil on the clutch face
(b) Weak or broken damper spring
(c) Poor contact of the disc surface or
excessively worn disc
(d) Warped pressure plate or flywheel
(e) Loose disc rivets
(f) Loose engine mounting
(g) Improper adjustment of the pitching
stopper
CL-29
CLUTCH SYSTEM
Corrective action
Replace.
Replace.
Replace.
Repair or replace.
Repair or replace.
Replace the clutch disc.
Repair or replace.
Replace.
Replace.
Replace.
Replace the clutch disc.
Replace the clutch disc.
Replace the faulty clutch disc.
Repair or replace.
Replace the clutch disc.
Retighten or replace mounting.
Adjust.