TDI Clutch Failure

Many TDIs are approaching or have already crossed the 150,000 mile, or even 200,000 mile mark.  If yours has a manual transmission, the flywheel and clutch assembly may be on their way out. Clutch life is highly variable, depending on driving conditions, and more importantly, driving style. Some clutches don’t last 100K miles. Is your clutch close to failing?

When do you need a new clutch?

Many of us know the feeling: you’re driving on a cold day, or after your latest power mod, and you roll into the accelerator in 4th or 5th at around 2000 RPM.  The tach needle climbs, but the speedometer needle doesn’t.  That’s clutch slip.

A clutch can slip for several reasons:

  • The friction material on the disk is worn, and when the pressure plate clamps down on it, it doesn’t create enough friction to prevent the disk from slowing down when engine torque is applied.
  • The pressure plate has lost some of its clamping force through wear or overheating cycles, and cannot clamp on the disk hard enough to prevent slippage
  • The flywheel or pressure plate surface has been compromised, either by overheating (usually from abuse) or contamination (from transmission or engine oil, or antifreeze) and does not allow the friction material on the disk to work properly
  • You’re putting more power through the clutch assembly and overpowering the clutch.

Or, you start your TDI and while it’s idling you hear a faint thumping from the front of the car.  When you open the hood the sound is more obvious.  Your dual mass flywheel (DMF) has failed.

A flywheel and clutch assembly is made up of four components: the flywheel, pressure plate, clutch disk and throwout bearing.  The flywheel is bolted directly to the crankshaft of the engine, and the pressure plate is bolted to the flywheel.  Both components always turn at engine speed.  The pressure plate is the clamp that pushes the clutch disk and flywheel together.  When the pressure plate starts squeezing the clutch disk against the flywheel, the clutch disk starts spinning.  The inner hub of the disk is attached to the input shaft of the transmission.  When the pressure plate clamps down on the disk, the disk spins at engine speed, the clutch is engaged, and the car moves.

This is common in TDIs as the clutch capacity was not much greater than the car’s stock power, and TDIs are easily modified for more power.  A chip tune, re-flash, and larger injectors, or a tune alone in Pumpe Deuse cars, is usually enough to overpower the stock assembly.

Other things can go wrong, too, such as springs failing in the flywheel, the throwout bearing failing, or the lever that pushes the bearing against the pressure plate.  These problems can cause the car to:

  • Not move because the clutch slips or fails to engage, or because a part of the clutch is broken and loose in the bell housing, preventing the clutch from operating
  • Make odd noises (thumping, squealing, rattling)
  • Not stop without stalling because the clutch will not disengage
  • Be difficult to drive (hard shifting, abrupt engagement, not full disengagement).

When these things happen it’s probably time for a new clutch.

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