955 CTT Vacuum/vent lines making creaking/chirping noise at idle RPM

[944sarethebest]

I had an oil change on the P!G (M1 synthetic) before a trip and that's when the trouble started...

 

The driver side wheel well makes a gentle creaking sound at idle RPM, which seems to disappear at higher RPM.  It sounded like a small frog quietly chirping in the wheel well and I was worried it was a turbo.  When we popped the hood, there was sound of a vacuum near the intake. The PCV to crankase hose (part #5) collapses while the engine is running and the oil fill port sucks strong vacuum if the fill cap is removed.

 

My local independent mechanic (I'm some distance from a Porsche specialist) found that hose 14 and 15 are both cracked and identified their failure as causing the sound.  Cause of failure is presumed age/heat. Since replacing those two components are $370-400 in hoses, is there something else we should be looking into as a cause of these pipe failures?  Searching the forums I came upon a discussion that makes me think maybe we should be looking at the PCV valve, air oil separator membrane, and the diverter valves?  I'm wrench-familiar with NA cars and new to turbos so I'd appreciate your input.  Is the restricted airflow or vacuum interruption causing turbo noise?  Has anyone else seen this and what else should I be checking?

 

We do see the boost gauge work normally or at least what it has historically (under acceleration it hits 0.8 bar/pegged and then holds near 0.6-0.7) before these issues started.  The rest of the car seems to work well, aside from the a sticky secondary air injection check valve on the passenger side.

 

Hoses 94810721753 and 94810721651 are cracked

 

 

2005 Cayenne V8 Twin Turbo

1085 944 early

Oklahoma

Edited October 6, 2021 by 944sarethebest
adding more detail