Hi,
I have posted this on a XC70 specific forum, but thought I might try to widen my search. I have a strange noise from my 2011 D5 in my XC70 and I suspected it was a vacuum issue. I removed the pump and replaced the seals but it is still the same.
With the brake booster pipe disconnected from the vacuum pump and the hole blocked I get a steady strong vacuum reading, but with the pipe connected, the vacuum meter needle flicker's So indicating a fault in the booster or pipework in that direction.
On the other hand, the popping/rattling noise is strong when the hole is blocked with the steady vacuum, and vanishes with the brake vacuum line removed from the vacuum pump.
Is anyone able to suggest what is going on? The two scenarios seem contradictory.
Link to how it sounds:
[YOUTUBE]
https://www.youtube.com/watch?v=deql5fLjHXY[/YOUTUBE]
Cab anyone suggest what it might be?
Thanks,
Tim.