mercedes 300E whining noise at startup, goes away after 30 seconds

[linedoggy]

I have a 1989 Mercedes 300E. It's running great, but on startup first thing in the morning, as soon as it goes into reverse gear, and in drive, I hear a not-too-loud whining sound from the left side of the engine. The sound goes away after about 30 seconds of driving. (I don't hear this sound at all again during the day while in use, but hear it only on startup upon gear engagement after sitting over night.) The car has good power and all electoral stuff works fine. I was wondering if anyone knew what it could be. Many thanks!

[Popeye]

Vacuum leak?

[rumb]

With a helper can you observe the engine when it is put into gear?

Need to try and narrow down where sound is coming from.

[Sugar Bear]

Does the noise occur if you don't put it in gear?

[linedoggy]

No, it sounds fine at startup, but as soon as it goes into gear, I hear the whine (or whirr), and it goes away after about 30 seconds of driving.

[linedoggy]

Today, it sounds pretty clearly like it's coming from the power steering. When I turned the steering wheel, I heard the whine/whirr sound, but the noise went away after about 30 seconds of driving.

[Sugar Bear]

Could be the power steering or the front pump in the transmission. The PS reservoir has a filter in the bottom that can get clogged. Replace the fluid and the filter and see what happens. If no joy, try a transmission fluid and filter replacement. I add Lubegard to transmission service, others avoid all additives but Lubegard works for me.

[rumb]

Sounds like PS pump. Check fluid levels.