TS-04, Troubleshooting - Clutch

Introduction

This troubleshooting guide is intented to help identify and repair problems with the clutch system. The following is a list of problem symptoms discussed in this guide:

944 CLUTCH HYDRAULIC SYSTEM

944 CLUTCH CONTROLS

Clutch pedal travels to floor with little or no resistance

Possible Causes
Checks
Procedure
Clutch master cylinder or slave cylinder is bad. The master or slave cylinder can fail due to an internal or external seal leak. The most common seems to be external seal leakage. Inspect the clutch master cylinder and slave cylinder for leakage and rebuild or replace if leaking.

One check you can perform on the master cylinder is to depress the clutch pedal while someone watches the brake fluid reservoir level. If the level rises while the clutch pedal is being depressed, 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 (leakage). Check for leakage from the fittings at the clutch master cylinder and the line from the clutch master cylinder down to the slave cylinder. N/A
Fluid in brake reservoir has dropped below the level of the hose going to the clutch master cylinder. Fill the brake fluid reservoir and bleed clutch if it feels spongy after filling. CLUTCH-02
Broken clutch relese lever Difficult to check but may be able to check by looking at the end of the relese lever in 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 requiring replacement. N/A

Clutch pedal feel soft when depressed

Possible Causes
Checks
Procedure
Air in the system. Normally a soft or spongy feel to the clutch when the pedal is depressed is the result of air in the system. Frequently this is caused by the brake fluid reservoir dropping below the level of the hose which goes from the brake reservoir to the clutch master cylinder. So, check the brake fluid level and fill if necessary. Then bleed the clutch using CLUTCH-02.

CLUTCH-02

Unable to engage transmission into gear

Possible Causes
Checks
Procedure
Bad clutch disc There's not really any way to determine positively that the clutch disc is bad. However, if you can not engage the transmission into any gear with the engine running but, can engage it into gear with the engine shutdown., that's a good sign that either the clutch disc or pressure plate is bad. You can get some indication of the condition of the clutch by performing a clutch disc wear check (CLUTCH-03).

Replace clutch (CLUTCH-01).

CLUTCH-03
CLUTCH-01
Bad pressure plate Like the clutch disc, there's not really any way to determine positively that the pressure plate is bad. Again, if you can not engage the transmission into any gear with the engine running but, can engage it into gear with the engine shutdown., that's a good sign that either the clutch disc or pressure plate is bad.

Replace clutch (CLUTCH-01).

CLUTCH-01
Transmission or shift linkage bad Refer to TS-05, Troubleshooting - Manual Transmission

TS-05

Clutch slips

Possible Causes
Checks
Procedure
Bad clutch disc The clutch disc can be worn or if the clutch disc is contaminated it will slip. The clutch disc can become contaminated by oil if you have a rear main oil seal leak. It can become contaminated by coolant if you have a leaking coolant hose at the back of the engine compartment.

Check for oil and coolant leaks around the back of the engine. Look for signs of oil or coolant coming out of the bottom of the clutch housing.

Check clutch disc wear using CLUTCH-03.

Replace clutch disc if there are signs of contamination or if the wear check is bad (CLUTCH-01).

CLUTCH-03
CLUTCH-01
Pressure plate or flywheel warped. If the flywheel or pressure plate are warped, the pressure plate will not have enough clamping force to keep the clutch disc pressed against the flywheel. There's really now way to check for this without disassembling the clutch and inspecting the flywheel and pressure plate.

CLUTCH-01
Clutch disc overheated. During heavy clutch usage (i.e. at the track), the clutch disc can become overheated causing it to slip. If you think that may be the case, allow it to cool for an hour or so and the clutch will likely stop slipping.

N/A

Clutch grabs or shudders as it is engaged

Possible Causes
Checks
Procedure
Clutch disc contaminated A contaminated clutch disc can cause the clutch to grab, shudder, or even slip. Check for oil and coolant leaks around the back of the engine. Look for signs of oil or coolant coming out of the bottom of the clutch housing.

Replace clutch disc if there are signs of contamination (CLUTCH-01).

CLUTCH-01
Driver induced shudder. Sometimes the way a car is driven can cause the clutch to be grabby or induce the shudder. There are basically two different types of drivers with regards to clutch operation. Those who feather the clutch and those who jab the clutch. Those who jab the clutch get on and off the clutch pedal very quickly when changing gears. Over time, this will tend the make the clutch grabby. Someone who feathers the clutch engages and disengages the clutch slowly. So, if you're one who normally feathers the clutch and you get in a car that's normally driven by someone who jabs the clutch, you'll likely notice a shudder when you engage the clutch. The advantage to gettting on and off the clutch quickly is that it normally extends the life of the clutch by reducing the amount of wear.

N/A
Warped pressure plate or flywheel. Again, there's really no way to check for this without disassembling the clutch and inspecting the pressure plate and flywheel.

CLUTCH-01
Worn splines on clutch disc. There's really no way to check for this without disassembling the clutch and inspecting the clutch disc.

CLUTCH-01

Noise or vibration coming from the area of the clutch

Possible Causes
Checks
Procedure
Bad release bearing or pilot bearing Excessive noise from the clutch area can be caused by a bad release bearing or pilot bearing. The clutch assembly must be disassembled to replace the bearings.

CLUTCH-01
Pressure plate bad.. A broken sping in the pressure plate can cause excessive noise and vibration. Replace clutch.

CLUTCH-01
Clutch disc bad. A broken spring in the clutch disc or a bad rubber centered clutch diaphragm can cause excessive vibration and noise. Only normally-aspirated 944s were equipped with the rubber centered clutch disc. Most people now days replace the rubber centered disc with the spring centered clutch discs when the clutch requires replacing.

CLUTCH-01

Clark's Garage 1998