Troubleshooting - Clutch
Symptom-driven guide to diagnosing clutch hydraulic and mechanical problems on the Porsche 944, including pedal feel, slipping, grabbing, and noise.
Vanskelighetsgrad: Middels5 min lesingGjelder for: 944 · 944S · 944S2 · 944 Turbo · 968
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Introduction
This troubleshooting guide is intended to help identify and repair problems with the clutch system. Symptoms covered:
- Clutch pedal travels to floor with little or no resistance
- Clutch pedal feels soft when depressed
- Unable to engage transmission into gear
- Clutch slips
- Clutch grabs or shudders as it is engaged
- Noise or vibration coming from the area of the clutch
Clutch System Overview
Clutch Pedal Travels to Floor With Little or No Resistance
| Possible Cause | Checks | Procedure |
|---|---|---|
| Clutch master cylinder or slave cylinder bad | The master or slave cylinder can fail due to internal or external seal leaks — external seal leakage is the more common failure mode. Inspect both for leakage and rebuild or replace if leaking. One check for the master cylinder: have someone watch the brake fluid reservoir level while you depress the clutch pedal. If the level rises as you depress the pedal, the clutch master cylinder is bad and should be rebuilt or replaced. | CLUTCH-04, CLUTCH-02 |
| Leaking hose or fitting | Check the condition of the hose from the brake fluid reservoir to the clutch master cylinder. Check for leakage at the master cylinder fittings and along the line down to the slave cylinder. | N/A |
| Fluid in brake reservoir has dropped below the hose intake level | Fill the brake fluid reservoir and bleed the clutch if it feels spongy after filling. | CLUTCH-02 |
| Broken clutch release lever | Difficult to check, but you may be able to inspect the end of the release lever through the round opening in the clutch housing. Try pushing on the end of the lever with a screwdriver — if it moves easily, the release lever may be broken and requires replacement. | N/A |
Clutch Pedal Feels Soft When Depressed
| Possible Cause | Checks | Procedure |
|---|---|---|
| Air in the system | A soft or spongy clutch pedal is normally the result of air in the system. This is frequently caused by the brake fluid reservoir dropping below the level of the hose going to the clutch master cylinder. Check the brake fluid level, fill if necessary, then bleed the clutch using CLUTCH-02. | CLUTCH-02 |
Unable to Engage Transmission Into Gear
| Possible Cause | Checks | Procedure |
|---|---|---|
| Bad clutch disc | There is no definitive way to confirm a bad clutch disc without disassembly. However, if you cannot engage any gear with the engine running but can engage with the engine off, either the clutch disc or pressure plate is likely bad. You can get some indication of disc condition by performing a clutch disc wear check (CLUTCH-03). | CLUTCH-03, CLUTCH-01 |
| Bad pressure plate | Same diagnosis approach as the clutch disc. If gears cannot be engaged with the engine running but can with it off, the pressure plate or clutch disc is suspect. | CLUTCH-01 |
| Transmission or shift linkage bad | Refer to TS-05, Troubleshooting - Manual Transmission. | TS-05 |
Clutch Slips
| Possible Cause | Checks | Procedure |
|---|---|---|
| Bad clutch disc | The disc may be worn or contaminated. Contamination can occur from a rear main oil seal leak or from a leaking coolant hose at the back of the engine compartment. Check for oil and coolant leaks around the back of the engine and look for signs at the bottom of the clutch housing. Check clutch disc wear using CLUTCH-03. Replace the clutch if contamination is present or if the wear check fails. | CLUTCH-03, CLUTCH-01 |
| Pressure plate or flywheel warped | A warped flywheel or pressure plate will reduce clamping force. There is no way to check for this without disassembling the clutch and inspecting both components. | CLUTCH-01 |
| Clutch disc overheated | During heavy clutch usage (e.g., track driving), the disc can overheat and slip temporarily. Allow the clutch to cool for an hour or so; it will likely stop slipping on its own. | N/A |
Clutch Grabs or Shudders As It Is Engaged
| Possible Cause | Checks | Procedure |
|---|---|---|
| Clutch disc contaminated | A contaminated disc can cause grabbing, shudder, or slipping. Check for oil and coolant leaks around the back of the engine and at the bottom of the clutch housing. Replace the clutch disc if contamination is found. | CLUTCH-01 |
| Driver-induced shudder | Driving style affects clutch feel. Drivers who engage and disengage the clutch quickly ("jabbing") tend to make the clutch grabby over time. If you normally feather the clutch and drive a car normally operated by someone who jabs the clutch, you will likely notice shudder on engagement. | N/A |
| Warped pressure plate or flywheel | No way to check without disassembling the clutch and inspecting both components. | CLUTCH-01 |
| Worn splines on clutch disc | No way to check without disassembling and inspecting the clutch disc. | CLUTCH-01 |
Noise or Vibration Coming From the Area of the Clutch
| Possible Cause | Checks | Procedure |
|---|---|---|
| Bad release bearing or pilot bearing | Excessive noise from the clutch area can be caused by either bearing. The clutch must be disassembled to replace them. | CLUTCH-01 |
| Pressure plate bad | A broken spring in the pressure plate can cause excessive noise and vibration. Replace the clutch. | CLUTCH-01 |
| Clutch disc bad | A broken spring in the clutch disc or a deteriorated rubber-centered clutch diaphragm can cause excessive vibration and noise. Only normally-aspirated 944s were originally equipped with the rubber-centered clutch disc. The spring-centered disc is the standard replacement when the clutch requires renewal. | CLUTCH-01 |
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