Jeep Cherokee (XJ): Diagnosis and testing

Safety precautions

WARNING: EXERCISE CARE WHEN SERVICING CLUTCH COMPONENTS. FACTORY INSTALLED CLUTCH DISCS DO NOT CONTAIN ASBESTOS FIBERS. DUST AND DIRT ON CLUTCH PARTS MAY CONTAIN ASBESTOS FIBERS FROM AFTERMARKET COMPONENTS. BREATHING EXCESSIVE CONCENTRATIONS OF THESE FIBERS CAN CAUSE SERIOUS BODILY HARM. WEAR A RESPIRATOR DURING SERVICE AND NEVER CLEAN CLUTCH COMPONENTS WITH COMPRESSED AIR OR WITH A DRY BRUSH.

EITHER CLEAN THE COMPONENTS WITH A WATER DAMPENED RAGS OR USE A VACUUM CLEANER SPECIFICALLY DESIGNED FOR REMOVING ASBESTOS FIBERS AND DUST. DO NOT CREATE DUST BY SANDING A CLUTCH DISC. REPLACE THE DISC IF THE FRICTION MATERIAL IS DAMAGED OR CONTAMINATED.

DISPOSE OF ALL DUST AND DIRT CONTAINING ASBESTOS FIBERS IN SEALED BAGS OR CONTAINERS. THIS WILL HELP MINIMIZE EXPOSURE TO YOURSELF AND TO OTHERS. FOLLOW ALL RECOMMENDED SAFETY PRACTICES PRESCRIBED BY THE OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION (OSHA) AND THE ENVIRONMENTAL SAFETY AGENCY (EPA), FOR THE HANDLING AND DISPOSAL OF PRODUCTS CONTAINING ASBESTOS.

Installation methods and parts usage

Distortion of clutch components during installation and the use of non-standard components are common causes of clutch malfunction.

Improper clutch cover bolt tightening can distort the cover. The usual result is clutch grab, chatter and rapid wear. Tighten the cover bolts as described in Removal and Installation section.

An improperly seated flywheel and/or clutch housing are additional causes of clutch failure. Improper seating will produce misalignment and additional clutch problems.

The use of non-standard or low quality parts will also lead to problems and wear. Use recommended factory quality parts to avoid comebacks.

A cocked pilot bearing is another cause of clutch noise, drag, hard shifting, and rapid bearing wear.

Always use an alignment tool to install a new bearing.

This practice helps avoid cocking the bearing during installation.

Clutch diagnostic information

Unless the cause of a clutch problem is obvious, accurate problem diagnosis will usually require a road test to confirm a problem. Component inspection (Fig. 8) will then be required to determine the actual problem cause.

During a road test, drive the vehicle at normal speeds. Shift the transmission through all gear ranges and observe clutch action. If chatter, grab, slip, or improper release is experienced, remove and inspect the clutch components. However, if the problem is noise or hard shifting, further diagnosis may be needed as the transmission or another driveline component may be at fault. Careful observation during the test will help narrow the problem area.

Clutch diagnostic information

Clutch contamination

Fluid contamination is a frequent cause of clutch malfunctions. Oil, water, or clutch fluid on the clutch disc and pressure plate surfaces will cause chatter, slip and grab.

During inspection, note if any components are contaminated with oil, hydraulic fluid, or water/road splash.

Oil contamination indicates a leak at either the rear main seal or transmission input shaft. Oil leakage produces a residue of oil on the housing interior and on the clutch cover and flywheel. Heat buildup caused by slippage between the cover, disc and flywheel, can sometimes bake the oil residue onto the components. The glaze-like residue ranges in color from amber to black.

Road splash contamination means dirt/water is entering the clutch housing due to loose bolts, housing cracks, or through hydraulic line openings. Driving through deep water puddles can force water/road splash into the housing through such openings.

Clutch fluid leaks are usually from damaged slave cylinder push rod seals. This type of leak can only be confirmed by visual inspection.

Improper clutch release or engagement

Clutch release or engagement problems are caused by wear, or damage to one or more clutch components.

A visual inspection of the release components will usually reveal the problem part.

Release problems can result in hard shifting and noise. Items to look for are: leaks at the clutch cylinders and interconnecting line; loose slave cylinder bolts; worn/loose release fork and pivot stud; damaged release bearing; and a worn clutch disc, or pressure plate.

Normal condensation in vehicles that are stored or out of service for long periods of time can generate enough corrosion to make the disc stick to the flywheel, or pressure plate. If this condition is experienced, correction only requires that the disc be loosened manually through the inspection plate opening.

Engagement problems usually result in slip, chatter/ shudder, and noisy operation. The primary causes are clutch disc contamination; clutch disc wear; misalignment, or distortion; flywheel damage; or a combination of the foregoing. A visual inspection is required to determine the part actually causing the problem.

Clutch misalignment

Clutch components must be in proper alignment with the crankshaft and transmission input shaft.

Misalignment caused by excessive runout or warpage of any clutch component will cause grab, chatter and improper clutch release.

Clutch housing misalignment

Clutch housing alignment is important to proper clutch operation. The housing maintains alignment between the crankshaft and transmission input shaft. Misalignment can cause clutch noise, hard shifting, incomplete release and chatter. It can also result in premature wear of the pilot bearing, cover release fingers and clutch disc. In severe cases, misalignment can also cause premature wear of the transmission input shaft and front bearing.

Housing misalignment is generally caused by incorrect seating on the engine or transmission, loose housing bolts, missing alignment dowels, or housing damage. Infrequently, misalignment may also be caused by housing mounting surfaces that are not completely parallel. Misalignment can be corrected with shims.

Clutch flywheel runout

Check flywheel runout whenever misalignment is suspected. Flywheel runout should not exceed 0.08 mm (0.003 in.). Measure runout at the outer edge of the flywheel face with a dial indicator. Mount the indicator on a stud installed in place of one of the flywheel bolts.

Common causes of runout are:

  •  heat warpage
  •  improper machining
  •  incorrect bolt tightening
  •  improper seating on crankshaft flange shoulder
  •  foreign material on crankshaft flange

Flywheel machining is not recommended. The flywheel clutch surface is machined to a unique contour and machining will negate this feature. However, minor flywheel scoring can be cleaned up by hand with 180 grit emery, or with surface grinding equipment.

Remove only enough material to reduce scoring (approximately 0.001 - 0.003 in.). Heavy stock removal is not recommended. Replace the flywheel if scoring is severe and deeper than 0.076 mm (0.003 in.). Excessive stock removal can result in flywheel cracking or warpage after installation; it can also weaken the flywheel and interfere with proper clutch release.

Clean the crankshaft flange before mounting the flywheel. Dirt and grease on the flange surface may cock the flywheel causing excessive runout. Use new bolts when remounting a flywheel and secure the bolts with Mopart Lock And Seal. Tighten flywheel bolts to specified torque only. Overtightening can distort the flywheel hub causing runout.

Clutch cover and disc runout

Check the clutch disc before installation. Axial (face) runout of a new disc should not exceed 0.50 mm (0.020 in.). Measure runout about 6 mm (1/4 in.) from the outer edge of the disc facing. Obtain another disc if runout is excessive.

Check condition of the clutch before installation. A warped cover or diaphragm spring will cause grab and incomplete release or engagement. Be careful when handling the cover and disc. Impact can distort the cover, diaphragm spring, release fingers and the hub of the clutch disc.

Use an alignment tool when positioning the disc on the flywheel. The tool prevents accidental misalignment which could result in cover distortion and disc damage.

A frequent cause of clutch cover distortion (and consequent misalignment) is improper bolt tightening.

Clutch diagnosis charts

The clutch inspection chart (Fig. 8) outlines items to be checked before and during clutch installation.

Use the chart as a check list to help avoid overlooking potential problem sources during service operations.

The diagnosis charts describe common clutch problems, causes and correction. Fault conditions are listed at the top of each chart. Conditions, causes and corrective action are outlined in the indicated columns.

The charts are provided as a convenient reference when diagnosing faulty clutch operation.

DIAGNOSIS CHART

CONDITION

POSSIBLE CAUSES

CORRECTION

Disc facing worn out
  1. Normal wear.
  2.  Driver frequently rides (slips) the clutch. Results in rapid overheating and wear.
  3.  Insufficient clutch cover diaphragm spring tension.
  1.  Replace cover and disc.
  2.  Replace cover and disc.
  3.  Replace cover and disc.
Clutch disc facing contaminated with oil, grease, or clutch fluid.
  1. Leak at rear main engine seal or transmission input shaft seal.
  2.  Excessive amount of grease applied to the input shaft splines.
  3. Road splash, water entering housing.
  4. Slave cylinder leaking.
  1.  Replace appropriate seal.
  2.  Remove grease and apply the correct amount of grease.
  3.  Replace clutch disc. Clean clutch cover and reuse if in good condition.
  4. Replace hydraulic clutch linkage.
Clutch is running partially disengaged
  1. Release bearing sticking or binding and does not return to the normal running position.
  1. Verify failure. Replace the release bearing and transmission front bearing retainer as necessary.
Flywheel below minimum thickness specification.
  1. Improper flywheel machining. Flywheel has excessive taper or excessive material removal.
  1. Replace flywheel.
Clutch disc, cover and/or diaphragm spring warped or distorted.
  1. Rough handling. Impact bent cover, spring, or disc.
  2. Improper bolt tightening procedure.
  1.  Replace disc or cover as necessary.
  2.  Tighten clutch cover using proper procedure.
Facing on flywheel side of disc torn, gouged, or worn.
  1. Flywheel surface scored or nicked.
  2. Clutch disc sticking or binding on transmission input shaft.
  1.  Correct surface condition if possible. Replace flywheel and disc as necessary.
  2.  Inspect components and correct/replace as necessary
Clutch disc facing burnt. Flywheel and cover pressure plate surfaces heavily glazed.
  1. Frequent operation under high loads or hard acceleration conditions.
  2.  Driver frequently rides (slips) clutch. Results in rapid wear and overheating of disc and cover.
  1.  Correct condition of flywheel and pressure plate surface. Replace clutch cover and disc. Alert driver to problem cause.
  2.  Correct condition of flywheel and pressure plate surface. Replace clutch cover and disc. Alert driver to problem cause.
Clutch disc binds on input shaft splines.
  1. Clutch disc hub splines damaged during installation.
  2.  Input shaft splines rough, damaged, or corroded.
  1.  Clean, smooth, and lubricate hub splines if possible. Replace disc if necessary.
  2.  Clean, smooth, and lubricate shaft splines if possible. Replace input shaft if necessary.
Clutch disc rusted to flywheel and/or pressure plate.
  1. Clutch not used for and extended period of time (e.g. long term vehicle storage).
  1. Sand rusted surfaces with 180 grit sanding paper. Replace clutch cover and flywheel if necessary.
Pilot bearing seized, loose, or rollers are worn.
  1. Bearing cocked during installation.
  2.  Bearing defective.
  3.  Bearing not lubricated.
  4.  Clutch misalignment.
  1.  Install and lubricate a new bearing.
  2. Install and lubricate a new bearing.
  3. Install and lubricate a new bearing.
  4. Inspect clutch and correct as necessary. Install and lubricate a new bearing.
Clutch will not disengage properly. 1
  1. Low clutch fluid level.
  2. Clutch cover loose.
  3. Clutch disc bent or distorted.
  4. Clutch cover diaphragm spring bent or warped..
  5.  Clutch disc installed backwards.
  6. Release fork bent or fork pivot loose or damaged.
  7. Clutch master or slave cylinder failure.
  1.  Replace hydraulic linkage assembly.
  2. Follow proper bolt tightening procedure.
  3. Replace clutch disc.
  4.  Replace clutch cover
  5. Remove and install clutch disc correctly.
  6.  Replace fork or pivot as necessary.
  7.  Replace hydraulic linkage assembly.
Clutch pedal squeak.
  1. Pivot pin loose.
  2.  Master cylinder bushing not lubricated.
  3.  Pedal bushings worn out or cracked.
  1.  Tighten pivot pin if possible. Replace clutch pedal if necessary.
  2. Lubricate master cylinder bushing.
  3.  Replace and lubricate bushings.
Clutch master or slave cylinder plunger dragging andør binding
  1. Master or slave cylinder components worn or corroded.
  1. Replace clutch hydraulic linkage assembly.
Release bearing is noisy.
  1. Release bearing defective or damaged.
  1.  Replace release bearing.
Contact surface of release bearing damaged.
  1. Clutch cover incorrect or release fingers bent or distorted.
  2. Release bearing defective or damaged.
  3. Release bearing misaligned.
  1.  Replace clutch cover and release bearing.
  2. Replace the release bearing.
  3. Check and correct runout of clutch components. Check front bearing sleeve for damage/ alignment. Repair as necessary
Partial engagement of clutch disc. One side of disc is worn and the other side is glazed and lightly worn.
  1. Clutch pressure plate position incorrect.
  2. Clutch cover, spring, or release fingers bent or distorted.
  3. Clutch disc damaged or distorted.
  4.  Clutch misalignment.
  1. Replace clutch disc and cover.
  2.  Replace clutch disc and cover.
  3.  Replace clutch disc.
  4. Check alignment and runout of flywheel, disc, pressure plate, andør clutch housing. Correct as necessary.

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