I am trying to identify a sound from my engine bay. It reminds me of escaping steam. My car:
1980 300SD (w116/120)
The sound is mostly (if not only) noticeable at idle and does not dissappear as the engine warms. I thought that it could be a bearing failing in something like a water pump, but nothing is getting warm to touch, and there appears to be no freeplay.
It doesn't have the high-pitched squeal of a loose belt.
It seems to be coming from the area around the air conditioner compressor (right hand side of engine if facing car).
Cchrismears, could the sound be a vacuum leak? I believe the diesels have to use a vacuum pump to control the engine cut-off and the automatic transmission changes that the 'gas' engines tap off from the inlet manifold.