General clutch diagnosis and solution
Symptom:
Clutch drags. It won't release completely and the transmission grinds when
shifted
| Possible diagnosis | Likely solution |
| Linkage out of adjustment or binding | Adjust or repair linkage |
| Release arm too long for the linkage system | Determine the correct ratio (as per instructions above) and shorten the arm |
| Release arm sitckout angle incorrect | Change the length of the release nearing, pivot or both, if necessary |
| Release arm hits bellhousing opening preventing full travel of the arm | Grind clearance as necessary on the bellhousing |
| Engine is shifting on the motor mounts, wasting linkage travel | Repair, rebuild or replace the motor mounts as necessary |
| Pilot bushing binding on the input shaft. Possibly damaged at installation or resulting from a misaligned bellhousing | Replace the pilot bushing. Refer to the bellhousing alignment procedure in the Novak guide |
| Input shaft pilot is "bottoming out" in the crankshaft bore | Shorten the input shaft by grinding or deepen the bore of the crank by drilling |
| Clutch disc hub is damaged or assembled incorrectly | Replace the disc |
| Pressure plate or cover is warped | Replace the pressure plate assembly |
| Excessive run-out at the face of the flywheel | Check the crank flange for burrs and remove them, or reface the flywheel |
| Incorrect flywheel to crank hub bolts. The bolt heads are driving the disc | Use the correct, special flywheel bolts |
| Clutch disc is installed backwards. The bolt heads are driving the disc | Disassemble and turn the disc around |
| Clutch disc is too large. The edge of the disc is interfering with the pressure plate assembly | Specify a smaller disc or turn down the edge of the existing unit |
| Clutch arm to throwout bearing retaining clip is tweaked on the bearing lip (progressive worsening) | Replace throwout bearing if damaged and reinstall the arm and clips correctly |
Symptom:
Clutch Slippage
|
Possible
Diagnosis
|
Likely
Solution
|
|
Linkage out of
adjustment or binding
|
Adjust the
linkage to create proper amount of slack in the system
|
|
Release
bearing is too long, holding the clutch in a slightly disengaged position
|
Use a shorter
release bearing. See the chart in the text
|
|
The friction
surface on the flywheel, pressure plate or disk is glazed (usually from
heat)
|
Resurfacing
and replacement of clutch assembly
|
|
The clutch is
too small and/or the spring load is too light
|
Use a larger
clutch or a heavier spring. The former is often preferable. Extreme cases
may require both
|
|
Oil on the
clutch disc
|
Repair the oil
leak (typically the engine rear main or oil pan if not the transmission
from seal) and replace the disc
|
|
Broken or
fatigued springs
|
Replace the
pressure plate
|
Symptom:
Clutch chatters when engaging
| Possible diagnosis | Likely solution |
| Damper springs in the clutch disc hub or the marcel spring between the facings is fatigued | Replace the clutch disc |
| Friction surface on the flywheel or pressure plage is glazed from the heat | Resurface or replace as necessary |
| Clutch disc is running out on the input gear (hub problem) | Replace the clutch disc |
| The flywheel or pressure plate surface is running out | Reface or replace as required |
| Oil on friction surfaces | Repair the oil leak (typically the engine rear main or oil pan if not the transmission from seal) and replace the disc. Avoid parts contamination upon reassembly |
| Linkage works erratically | Inspect the linkage, paying special attention to the holes in each lobe. Repair or change the linkage as required |
| Play in the motor mounts allowing for shifting of the powertrain, relative to the linkage | Change or repair the motor mounts |
Symptom:
Pedal pulsates when pushed to floor (3-finger coil spring type only)
| Possible diagnosis | Likely solution |
| Clutch is over-releasing and the release fingers are hitting the disc hub damper springs | Reduce linkage travel (see above text) |
Symptom:
Pedal pulsates at start of release
| Possible diagnosis | Likely solution |
| Flywheel run-out | Check for burrs on clutch and flywheel mounting flanges |
| If a three-finger type, fingers may not all be the same height | Have the pressure plate readjusted by a rebuilder or replace the pressure plate |
| Excessive clearance between release bearing and retainer | Replace the retainer or on mismatched parts, sleeve retainer up to the release bearing size, plus slip fit |
Symptom:
Noise; clicking or rattling at idle RPM with the pedal released
|
Possible
diagnosis |
Likely solution |
| Broken spring(s) | Replace the pressure plate |
Symptom:
Noise; whirring or grinding when clutch is released (pedal depressed)
| Possible diagnosis | Likely solution |
| Failing clutch release bearing | Replace |
Symptom:
Noise; chattering or "buzzing" when clutch is released
| Possible diagnosis | Likely solution |
| Excessive pilot bushing to input gear clearance. Often resultant of bellhousing misalignment | Replace pilot bushing. Clearance should be .001 to .004 |
Symptom:
Pedal is hard to push and hold down
| Possible diagnosis | Likely solution |
| Improperly set-up linkage system | Change as required (see text) |
| Pressure plate spring load excessive for linkage | Reduce spring load, or, if high pressure clutch is required then modify the linkage to give the minimum travel that will still release (i.e., provide the required .025 air gap) and leave a finger clearance of 1/16" |