I have an 08' CTT with PDCC and one without...the difference has been driving me crazy...I thought I had a bad power steering pump or maybe even a marginal water pump. Now after reading this, I am glad to read it's the PDCC!

 

Resurrecting old thread here:

The Cayenne models equipped with PDCC will have a slightly more noticable 'hum' at idle from the hydraulic pump however I believe the 'hum' that some are reporting is significantly louder than normal.

The hydraulic pump on PDCC Cayenne is a tandem pump. This means the same pump creates hydraulic pressure for the PDCC system and the power steering system. Each system has its own set of hydraulic lines and each has its own reservoir. The hydraulic fluid in each system never mixes. The reservoir is identical for the PDCC and the power steering. The reservoir contains a built in filter for the hydraulic fluid.

According to the Porsche Service Manual, the PDCC reservoir must be changed every 48,000 miles (77,250 kms) or no later than 6 years.

Failing to change the PDCC reservoir may affect the PDCC side of the hydraulic pump. It is weird that there is no indication in the manual to replace the power steering reservoir.

The part # for the reservoir(s) is: 955-314-015-20

 

The problem is not the pump. The piece of pipe from the deposit to the first metallic pipe near the pump, intake to the pump, is the cause of the vibration.
this pipe is a rubber pipe, if you press it with your fingers reduce the noise.
Two solutions, press the tube with some metallic
Twizers or find a new pipe a little bit thinner or maybe from other brand.
sorry about my english