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1983 300SD Power Steering Noise

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Dacob Paine

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1983 300SD
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Discussion starter · #1 ·
Hello everyone, thank you all so very much for all of the hard work you all put in to help people with their questions. It is very much appreciated.

I recently purchased a 1983 300SD. I don't have a baseline to judge from as this is my first MBZ. After warming up each morning for about 10 minutes at 1000 RPM, I pull out of my parking spot and I hear some whining from the power steering. After driving for a bit the whining subsides. There's no reservoir for the power steering so I'm not sure if the fluid is low. It appears from the manual that the power steering fluid is ATF. I'm not sure how much the ATF is expanding in volume as it warms up.

Should I be concerned? The whine does go away after the motor is fully warm, but I'm not sure if this sound is normal. This car is my only car and it's my new baby, so I really want to maintain it as well as possible. The whine seems to be more pronounced when rotating the steering wheel to the left. I don't know why the whine would be asymmetrical.

Any suggestions would be most welcome. Thank you very much for your time.
 
Discussion starter · #2 ·
Update

OK, should have done my homework before posting, sorry about that. I found the power steering box and checked the level, the fluid is clean and clear as can be, must have been flushed recently. Likely filter was changed too.

Now just not sure what level the fluid should be at when it's cold, I could not find a low or high marker on the inside. It's a couple of inches down from the top. Still not sure if the whine is normal but if the fluid is very clear and not worn so that's great.

Any idea how full the reservoir should be? I'll go do some more homework now to see if I can find any info.
 
Discussion starter · #4 ·
OK, it was very low. I did not have power steering fluid so I used ATF. However the rag I used was not lint free and I contaminated the fluid with tiny rag bit floaters. And of course now I have a mix of power steering fluid and ATF in there. I decided not burning out the power steering or loosing control and killing someone was more important. So now I'll have to flush the system on Saturday to get the rag bits and ATF out. Ah well. Looks like an easy process. Too bad... I should have been more careful. I'm pretty sure the ledge that sticks out is the high mark so I stayed below that. Kinda mad at myself for contaminating it but I think the filter will catch some of the rag bits. They are floating so hopefully they'll keep floating for the next two days or get caught in the filter.
 
#5 ·
I'd suggest changing all the fluid out. Get a fluid extractor, open up the PS res, remove the filter, and suck all the fluid out. Lift the front of the car up. Turn the wheel all the way to the left, and suck out the fluid which is pushed into the res. Now turn the wheel right, and repeat. Do this until no more fluid shows up in the res.

Now pour in your new fluid. Turn the wheel back and forth several times. Now suck the fluid out, and repeat above, trying to remove all the 1/2 dirty fluid. Refill, and repeat until the fluid stays clean.

Put the filter back in, secure it, refill, and start the engine. The dirty fluid which was in the cooler will now get mixed in. Suck the fluid out (it helps if your extractor has a small hose so it can go through the holes in the filter), refill, and run again. As before, do this until the fluid stays clean.

I suggest using a green CHF 11S type fluid. It's leaps and bounds better than ATF for a power steering system (better lubricity, *much* more stable over time). On my SDL 2L was enough to flush the system. I used the first liter doing the initial flushes before starting the motor, and 1/2 of the 2nd liter after starting the motor.

-J
 
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#6 ·
Actually Mobil 1 ATF is much better suited for power steering than the CHF and its commonly available.
 
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Discussion starter · #7 ·
Absolutely excellent info, thank you so much. I found a YouTube video where a guy disconnected the return line, puts in an empty gallon oil jug, then runs the motor while pouring two quarts at a time of fluid into the res. Not good. If the flow rate of the new fluid is slower than what's coming out of the return, you risk running the pump dry and damaging it. Your process of multiple exchanges is much safer. I'll order a hand actuated syphon pump tomorrow along with a new filter. Can't find them at my local auto supply. I'll look into the suggested PS fluids. I think it's running ATF now as it's a clear red liquid. There is definitely a leak in the system. I thought I had a transmission leak but it's fine, it's coming from the PS. It leaks about 20 drops a day from under the chassis. I also overfilled the transmission ATF so I have an appropriate next week for an ARF fluid and filter change. They'll check the transmission seals too.
 
Discussion starter · #8 ·
One question. I don't have a floor jack. Is raising the front end to exchange all the fluid mandatory? Or will going lock to lock 10 times or so enough to cycle all the fluid through the whole system?
 
#10 ·
Forcedinduction said:
Actually Mobil 1 ATF is much better suited for power steering than the CHF and its commonly available.
Click to expand...
I've got both fluids. I'll pour some of each on a pan and let them sit, we'll see which one goes gummy first :nerd

-J
 
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#11 · (Edited)
Right, because hydraulic systems have a large flat surface area that sits exposed to the open air for long periods of inactivity.

Your comment makes total sense.

Dacob Paine said:
One question. I don't have a floor jack. Is raising the front end to exchange all the fluid mandatory? Or will going lock to lock 10 times or so enough to cycle all the fluid through the whole system?
Click to expand...
Taking the wheels off the ground means you can turn the wheels without running the pump so you don't risk running it out of fluid.

The proper exchange method:
Lift the front end off the ground.
Remove the filter and suck all the fluid out of the reservoir.
Remove the return hose off the reservoir nipple and place it in a container.
Angle the return nipple up so fluid won't run out of the reservoir.
Fill the reservoir with new fluid.
Turn the wheel lock to lock as many times as needed until the fluid coming out is clean.
Reattach the return line.
Install new filter.
Top up the fluid.
Turn the wheels several times.
Top up the fluid.
 
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Discussion starter · #12 ·
Got it, thank you. Since I can't lift it, what if I remove the fluid from the res, remove the filter, refill it with clean fluid, cap it, run the motor, cycle lock to lock 10 times, then syphon off the fluid, refill with clean and repeat as many times as needed until the fluid is clear, the put in new filter and top off until under high mark a bit? Seems that'll achieve the same result but of course it'll require more time, perhaps 5 to 10 repeats. May not get all contamination out but should get almost all. Then new filter can capture remaining contamination as it's driven?
 
#14 ·
Dacob Paine said:
And perhaps lubricated sheet metal under tires to reduce wear on tires when rotating so I don't rub off too much rubber?
Click to expand...
Just lift the front of the car off the ground... set the parking brake and put a jack under each jack pad. You won't be going under the car, so jackstands won't be needed.

And I'll stick by my CHF-11S recommendation. It's what late W126s came with from the factory, and what every Mercedes used until they went to electric power steering, and what VW changed to in the early 90s as well. Carquest and Amazon have it readily available.

-J
 
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#16 ·
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#18 ·
The point is CHF is NOT the correct fluid, ATF is.
 
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#19 ·
#20 ·
Forcedinduction said:
The point is CHF is NOT the correct fluid, ATF is.
Click to expand...
Again, CHF is what's specified for my 91. :confused: So if you want to argue with Mercedes be my guest. They changed the specification once CHF became available.

-J
 
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Forcedinduction
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