Ok so here is a head scrtacher.
My wifes 90' 560sel has had a hyrolic oil leak that has been on my list to take care of. Well she brings it home the other day and says my car is making a moaning noise. So I fire it up this morning and it's actually more like a train whistle sound just sitting there in idle. Fluids look reasonable noise seems to come from under the front but also the rear of the engine. Belts are tight, all moving accessory pieces (alt, AC) move freely. The noise is the same in all PNDL positions.

I've got the underbody soaking with engine degreaser, so I thought while I'm waiting I would check and see if anyone had ever heard this before.

Regards,
Bob

I would check your Hydraulic Pump/ Fluid Level. I bet your whistle is coming from the lack of fluid as it spins. Also, check your power steering pump, I had a Volvo 740 that would whistle (train whistle sound) when low on fluid...

__________________
My Work:
Mercedes-Benz Manhattan, Inc.
Business Development
536 West 41st Street
New York, NY 10036

-My Garage-
1996 E320: White 118,000 miles ~Dad's Driver~
1996 E320: Green 109,000 miles ~Mom's Driver~
~My Babies~
2000 SL500: Desert Sand 96,000 miles
-Previoulsy Judge Judy's-
2008 E350 4MATIC Sport
-Flint Grey/ Ash/ Black Birds Eye Maple-

The hydro fluid is a little low, certainly will accept more. Its been low before without the whistle so I hope that I haven't waited to long to find the leak.
So more fluid is on the list and I only hope that it will be that easy.
Well I've gotten the bottom degreased and it's almost done dripping so I'll climb under to see if I can find the leak source. Seems to be back toward the front or passenger side of the transmission.

Thanks for the quick response and the incite.
Regards,
Bob

Check your Trans Oil Cooler lines that go to the transmission for leaks...

What color is the fluid that is coming out?

__________________
My Work:
Mercedes-Benz Manhattan, Inc.
Business Development
536 West 41st Street
New York, NY 10036

-My Garage-
1996 E320: White 118,000 miles ~Dad's Driver~
1996 E320: Green 109,000 miles ~Mom's Driver~
~My Babies~
2000 SL500: Desert Sand 96,000 miles
-Previoulsy Judge Judy's-
2008 E350 4MATIC Sport
-Flint Grey/ Ash/ Black Birds Eye Maple-

It appears to be the hydraulic fluid line that are leaking.
The fluid is the clear hydro mixed with lots of under chassis dirt and grime.
I'm going to concetrate some more degreaser up front along the hydro lines to get them cleaner then let it run to see if I can pick up the leak.
Hey at least it isn't 20 deg outside crawling around on the ground.
Someday I'll get a decent garage.

Thanks for the feedback.
Regards,
Bob

I've had this on other cars where the power steering fluid gets low and you get air through the pump and rack. Sounds like you may have located your issue, but steering is always the first place I look.

Good luck -- let us know how it shakes out.

Cheers, John

__________________
'98 E300TD (W210) | Sold 6/09 with 205k and counting
'04 VW Touareg V10TDI

seems like the whistle comes from the small round hydraulic pump on the front of the engine just below the distributor.
A bear to work on so I agreed to let the better half take it to MB Reno.
A $100 later they had put together a laundry list of stuff wrong with the car quoted $4K to do the work.
so I'm considering pulling the engine and trannie out, I assume the two will come out together.
wife misses the car (she's driving my 87 300e) so I need to decide is this vehicle really worth all of the work and another $500 in parts.
can anyone recommend a good detailed manual for the 89 560sel (my CD MB 300e manual leaves a lot to be desired)????
Will the engine and tranny come out together????
Thanks for the help.
Regards,
Bob