c216 abc noises

[Brian with CL]

2011 CL500 Bluefficiency. 22,000 miles. Two garages unable to diagnose problem -
Loud groaning from somewhere to rear of near-side, sometimes after crossing a speed bump ( slowly ) or sometimes when down-shifting on long decline. On long incline, sometimes get revving noise from engine bay out of sync with engine speed. No warning lights. Noises come and go - sometimes severe - never when garages try to reproduce causes ( main dealer and long-trusted independant ). No leaks detected - ABC fluid level fine - no sagging

 

[donshl]

Gearbox mounts and subframe bushes?

 

[BlackC55]

it could be the accumulator on the ABC system. We have done a few now.

 

[Brian with CL]

Thanks - accumulator a possibility if it can fail noisily without an associated ABC warning light. When have a passenger in the rear seats they think the groaning comes from immediately behind them ... is the rear accumulator in that vicinity?

 

[Mr Kripling]

Pulsation damper?

 

[BlackC55]

Pulsation damper?

Same thing

It needs simple sound locating equipment and time.