Information on diagnostics

Rattling noises

due to oil sludge in the vacuum pump

My vehicle is rattling: Is there bearing damage to the crankshaft?



Pierburg no.

VW Transporter LT, T4

Vacuum pump


Potential complaints:
Rattling noises (like bearing damage on the crankshaft)

The piston vacuum pump is driven by the camshaft (1) through a connecting tappet (2). In the recommended installation position, the engine oil can flow back into the engine (Fig. 1). The installation position in the VW Transporter is as shown in Fig. 2.
If oil is not changed regularly, the engine oil ages. Oil sludge with viscous consistency builds up between piston crown and housing. This prevents the piston from reaching its end position. There is leeway between tappet and connecting tappet. This results in rattling noises, which sound like bearing damage on the crankshaft.


  • Intervals for changing oil not adhered to
  • Insufficient quality of engine oil
  • Soot formation due to unclean combustion
  • Faulty exhaust gas recirculation



In case of oil sludge deposits the vacuum pump must be replaced. It cannot be cleaned, as the vacuum pump cannot be opened with ordinary tools and there are no spare parts. A similar complaint occurs if the wrong vacuum pump is installed with a tappet (3) that is too short.

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