Signs of a dieing PS pump? - PeachParts Mercedes-Benz Forum

muleears · #1 11-09-2009, 05:32 PM

My 87 has started to make a whirring noise when turning right. Farther you turn the noisier it gets. Sounds normal when turned to the left. Proper fluid and level. To my knowledge this pump only has 349,000 miles on it so it can't be worn out, can it???

Seriously, could this be the steering box and not the pump? Maybe just trapped air?

TIA

sasquatchgeoff · #2 11-09-2009, 06:28 PM

The control valve in the gear has two sides, left and right. Without proper fluid maintenance, seals in steering boxes can go out. Pumps usually present problems regardless of steering direction.

muleears · #3 11-09-2009, 07:18 PM

I'm a dunce when it comes to the steering stuff on these cars. So what you are saying is that a seal on the steering box is failing (failed)? Wouldn't it leak? Would I be better off getting a new steering box from the yard or rebuild the existing one? If you can rebuild them. Thanks for the input.

sasquatchgeoff · #4 11-09-2009, 07:33 PM

In a strange coincidence, I was in the process of boning up on steering gear rebuild - which BTW is an extremely involved process. If the junkyard has one available you can usually get them for about $40. Since it is difficult to determine if a gear has a bad internal seal - short of complete failure of power steering, I have only been able to troubleshoot via process of elimination. Pumps can be pressure tested, and that is about the only way of determining output other than the "if it aint broke don't fix it" method.

If you have access to another working pump, put it on the car and try to see if you can duplicate the symptoms. If it behaves the same way, then you know it is the gear.

muleears · #5 11-09-2009, 07:51 PM

Sounds like a good idea. I'll see if I can find another pump to test it. Thanks

Jeremy5848 · #6 11-09-2009, 08:08 PM

Does not sound like the pump. Our '96 E300D (W210, OM606) has a failing pump, has had it for years. The symptom is that it provides insufficient boost to the steering at low (parking lot) speeds. At higher speeds all is well. No difference right or left.

In our case, failure is at least in part due to the fact that when we got the car at 248,000 miles with complete service records from all three POs, it was obvious from the black stuff in the PS pump reservoir and the lack of any records that the fluid had never been changed. A little research showed that the PS fluid is not part of any scheduled Mercedes service, hence it was never done. I flushed the system (no filter to replace in this year-model) and it got a little better. I plan to flush it again this month.

A seal problem would be an internal leak -- fluid would not escape from the steering box so you would not know until it caused a problem.

Jeremy