Whirring noise when I turn the wheels

[JasonP]

On my 1979 300SD, the past few days I have noticed a new sound - when I turn my wheels after first starting the car and pulling out, there is a whirring noise, or hum, or slight groan, coming from there. After the car is driven it is not so bad, but still sometimes occurs on very sharp turns.

The weather has turned cold lately, so temperature may have something to do with it.

Any ideas?

[Bandolero]

Sounds like the power steering pump, is the pump reservoir full?

[JasonP]

How do I check that?

[ptashek]

How do I check that?

Not sure about the diesels, but in the petrol models the reservoir is on the right hand side of the engine bay (when facing the windshield), at the top and close to the radiator, usually closed with a butterfly-type nut. Undo the nut, take off the cover and there should be a mark on the inside wall to which the reservoir should be filled.

[John Hubertz]

Most Mercedes of this era are a bit touchy about power steering fill level - I know in my 1977 even the slightest loss of fluid at all resulted in the noise you describe. 

Here's a picture of what Ptashek described (the pump with attached reservoir).  Note that they are almost never this clean...  so expect it to be black with grime and original paint.



Someone correct me if I'm wrong, but not only is power steering fluid change pretty much necessary when you buy any older car, but in the 116 isn't there some kind of a filter at the bottom of the reservoir that should be changed?

Brake fluid and rear axle lubricant are also an excellent idea when assuring an older car is ready for a few more years of service.  The problem isn't necessarily that the fluids are dirty or "worn out", but the tendency of all automotive fluids over time to attract water from condensation and infiltration of humidity.  Where water is, corrosion will inevitably begin to destroy parts.

[Casey]

Not sure about the diesels

They are identical.

[JasonP]

Yes, mine was covered with oil and grime.



And here is a peak inside.



Please tell me it is empty because the car has been sitting. 

[Casey]

Someone correct me if I'm wrong, but not only is power steering fluid change pretty much necessary when you buy any older car, but in the 116 isn't there some kind of a filter at the bottom of the reservoir that should be changed?

Yes. $9 at http://mercedessource.com/node/8811

Supposedly red ATF is more appropriate for these cars than the clear stuff from auto parts stores.  I don't know if there's any truth to that but when I started using generic power steering fluid to refill the leaking 450SE, it stopped leaking after a couple top-offs.  Given that I didn't actually fix the problem that seems really dodgy to me and I wouldn't recommend it.  I bought some of this stuff which I'll be using whenever I get new hose to repair the system properly (123's use a different hose width) and do a full flush:  http://mercedessource.com/node/6885

[Casey]

Please tell me it is empty because the car has been sitting. 

It's empty because the rubber hose that connects to the bottom of the pump needs replaced.  Inspect it and you'll find it's covered in fluid and cracks.  It can't cost much but MercedesSource only carries these for 123's and later - the 116 part is different so you'll have to find another source.

[JasonP]

Okay, I don't paid until Thursday. Is it possible for me to drive this car to work this week in this condition without causing further damage to it?

And this rubber hose - could I get it at an auto parts store and just replace it myself?

[Casey]

Please tell me it is empty because the car has been sitting. 

It's empty because the rubber hose that connects to the bottom of the pump needs replaced.  Inspect it and you'll find it's covered in fluid and cracks.  It can't cost much but MercedesSource only carries these for 123's and later - the 116 part is different so you'll have to find another source.

Actually maybe I'm wrong, because this page says it will fit 116's too:
http://mercedessource.com/node/671

I must have been trying some other hose I ordered from them to fix the 450SE.  Oops!

[Casey]

Okay, I don't paid until Thursday. Is it possible for me to drive this car to work this week in this condition without causing further damage to it?

And this rubber hose - could I get it at an auto parts store and just replace it myself?

If you keep driving it, I'd worry that you'll become unable to steer the car anymore.  Do you have any transmission fluid you can use to top it off?  If not I'd drive straight to the nearest auto parts store and buy some - top it off immediately and keep in the trunk.  You can just keep topping it off whenever it starts making noise until you fix the problem properly - it doesn't leak that fast and that shouldn't cause any damage.  I drive about 200 miles every day and would just top off the reservoir maybe once a week or so when it started making noise again.

I don't know about auto parts store hose - you probably could but I prefer to buy something online that's rated for the job than risking making a bad guess.

[JasonP]

I do have an unopened quart of DEX III/M automatic transmission fluid. Would this work? Would this be enough?

[Big_Richard]

.

[JasonP]

Major Tom - I do see in my service manual that ATF is fine. The filling capacity is 1.5 Liters, I only have a quart at home (946ml). Maybe this will be able to top it off for now.

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Well, it looks like the pump itself is not leaking. I see no wetness on the pump itself, even at the front seal. There are two hoses coming out of the pump:



And they both go into the power steering box:



As you can see from the previous picture, and the one below, one of these guys is wet:



Apparently this is the return hose. Mercedessource has this hose for $30.

http://www.mercedessource.com/node/671

Seems a bit pricey. It would be nice to find a cheaper option.