A slipping clutch is a relatively serious problem. Clutch slippage occurs when the pressure plate is not holding the disc tightly against the flywheel. If the clutch does not form a tight coupling between the engine and transmission when the pedal is released, you should perform some basic troubleshooting procedures to determine the cause of the problem. If you fail to resolve it quickly, it can lead to greater damage or extend to other parts. This will increase the cost of the eventual repair.
How to Test
If you believe that your clutch may be slipping, there is an easy way to test. Start the vehicle with the parking brake engaged. Now, attempt to stall the engine. Without giving it any gas, release the clutch pedal. The longer the engine runs, the worse the clutch is slipping. This test unfortunately compounds the problem.
The clutch is supposed to slip slightly while changing gears during normal driving. The slipping causes heat and friction, which wear on the clutch components. Eventually, some components will fail and the clutch will slip at inappropriate times. On the other hand, slipping in a brand new clutch indicates a defective or maladjusted installation.
Normal Wear and Tear
Clutch failure is expected with high mileage vehicles or parts. Refer to the manufacturer's maintenance schedule. You should be able to check the disc by lifting a cover on the clutch house. Replace the disc anytime it is worn to the rivets, or damaged by slipping from another source. Certain driving habits will increase regular wear on the clutch. Avoid resting your foot on the clutch pedal while driving.
Grease and oil on the disc can cause the clutch to slip. Check the crankshaft seal, and transmission input shaft seal for leaks. Once the leak is contained, clean off all of the clutch components. Replace the disc because the slippage will have damaged it.
Misaligned Release System
If the release bearing stays in contact with the pressure plate even after you lift your foot, the clutch may slip. This is a possibility on newly installed clutches. Check the linkages for rust, bent parts, and obstructions. Check for wear on the release bearings.
Broken Engine Mount
Check your engine mount to see if it is broken. A damaged engine mount can allow the engine to move. If it presses against the release bearing or binds the clutch linkage, this can cause the clutch to slip.
Other External Failure Points
Check other linkages and components of the clutch system. Look for wear on the pilot bearings, bushings, and fork. Trace the hydraulic lines and linkage cables for breaks or failures. Check the pressure plate and flywheel for cracks and corrosion or improper machining. Check for a defective cable adjuster or binding cylinder.
If the release system checks out, disassemble the clutch and transmission to check the internal components. Look for damaged springs or release levers inside the clutch assembly. Replace these if necessary and reassemble the clutch.