I want to use a turkey baster and remove the power steering fluid and exchange it several times over the course of a week. I have a w115 240D 1976 model. Should I use regular power steering fluid or use automatic transmission fluid? Will it hurt if while replacing the fuid with one or the other mixes while cycling out the fluid over the course of a week, Thanks for any advice.

If you really want it all out, try using the drain plug on the steering box.

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1981 240D 4sp manual. Ivory White.

I'd suggest sticking with the type that is in the system now. Either ATF (red) or PS fluid (amber/clear). Remove the filter in the bottom of the reservoir to get more fluid out and replace it with a new one on the first fluid exchange, it isn't necessary to renew the filter on each exchange.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Shern,

I'm not familiar with steering box drain plugs. Sounds like a good way to get low lying grit out. Are they on 123's, 124's. What size hex 14mm, 17mm?

Thanks!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

I’m pretty sure it’s a regular bolt at the bottom of the steering box. Remove the bolt then turn the steering wheel slowly stop to stop a few times.

IIRC it’s the same bolt replaced by a holding tool when checking wheel alignment.

Sixto
98 E320s sedan and wagon
02 C320 wagon

You can get it in one sitting if you have two people. Unbolt the low pressure line and stick it in a milk jug, jack the front end up and have someone inside the car turn the wheel back and forth while pouring in new PS fluid. Once the fluid cycles through the system and comes back out clear, you are good. Just don't let the pump run dry so make sure you are pouring fast enough.

I use this stuff. You can get it at NAPA.

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'80 300SD - '83 240D - '00 E55 AMG - '02 G500

To me the advantage of non-red fluid is it’s easier to see when it runs clean. Like alternating between blue and yellow brake fluid so it’s easier to see when the old stuff’s been flushed. Cue brake flush frequency debate.

And as someone said, ATF can claim to be backward compatible but the owner manual and engine bay tags aren’t necessarily forward compatible. Dex III came out in the early ‘90s so it can’t be exactly what MB engineers specified for a W115. Then again neither did they specify stuff labeled as PS fluid. I guess a clean dose of what’s worked for you for years can’t cause harm.

Sixto
98 E320s sedan and wagon
02 C320 wagon

I used both the Valvoline and Prestone which stopped leaking in a snap, and that was 10 years ago.

This is one of those jobs where a topsider really helps. Stick the suction hose into the reservoir, draw out the fluid, fill, run awhile, repeat.

I mean, you can put power steering fluid in your transmission too right?

Just a datapoint...

I switched to this stuff in my SDL when I cleaned and flushed the system out based on recommendations of this forum. About a month later I went from a PS system that was bone dry to literally raining under my car. We're talking enough to deplete the reservoir in 3-4 days.

I switched back to ATF, and after about a week, no more leak. It hasn't used a drop since. I did nothing else but switch fluids.

If the system has ATF in it now, be wary of switching to something else, it may carry unintended consequences.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]

This needs a little dissecting:

1) Did you replace what was in the reservoir? Flush through the return hose?

2) Where was the leak? What did you repair or replace?

Seems like the answer to 2 is you switched back to ATF and let it fix itself. Not meaning offence, that’s a strange course of (in)action for a keeper.

In retrospect switching to PS fluid might be why the weeping pitman arm seal of the ‘87 300D wept worse. I replaced that seal and all was well.

Sixto
98 E320s sedan and wagon
02 C320 wagon

The system was flushed until clear. The fluid I replaced was not in bad shape, still red and clear. Repeated flush after 2-3 days of driving. Replaced filter.

Major leaks were at the steering box itself. Pitman arm seal and heavy leaks from the top cover gasket. Very slight "sweat" around the input shaft seal on the pump. Most leaks were concentrated to "everywhere" on the steering box.

I read (don't remember where) about the potential for leaks when switching fluids in the PS system. Since the system was tight before the flush/refill, I decided to flush it back out and convert back to ATF. That's literally all I did. I can only assume that the additives and viscosity are different between the PS fluid and ATF so that while the system is tight with ATF, it leaks like a sieve with the PS fluid.

I'm not stating this will happen to everyone, but it sure happened to me. After the leaks stopped again, it hasn't left a drop anywhere and the box is bone dry again.

Your mileage may vary...

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]

I rebuild these boxes regularly.

I use ATF in my rebuilds, but PS fluid is fine as well. Here's the approved list.

MB Power Steering Fluid MB Part No. BQ 1 46 0001
or
Approved Dexron III Automatic Transmission Fluid (Note 1)
Castrol Dexron-III/Mercon ATF F-30341
Castrol Transmax M-22257/22096
Chevron ATF Dexron III F-30108/30159
Citgo Multi-Purpose ATF D-21571
Exxon Superflo ATF Dexron III F-30111
Havoline ATF Mercon/Dexron-III F-30321
Texaco ATF Mercon/Dexron-III F-30321
Pennzoil ATF D-22413/F-30110
Quaker State Dexron-III/Mercon F30161
Sunoco ATF Dexron-III/Mercon F-30176
Unocal Multi-Purpose ATF D-22413/22431
Valvoline ATF Type D

I have a friend who has used the SLS hydraulic fluid in his boxes and I have to say that I appreciated the cleanliness of the inside of his boxes when I rebuilt them. I haven't tried this on my own boxes yet so I can't report back on the effectiveness.

DO NOT use anything with stop leak. This contains a chemical which causes the seals to swell. It does make old seals more pliable and easier for me to remove when I'm rebuilding a box, but rarely does it stop the box from leaking. Also, if its in the system then its not just the seals in the box which are going to swell and deteriorate, but also the ones in the pump.

If your box is leaking you need a rebuild. The box is part of a high pressure system and if fluid can get out it will get out. The most common leak point is the pitman arm shaft axial seal.

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Onus probandi incumbit ei qui dicit, non ei qui negat

I recondition w123/w126/w124/w140/r107/r129/ steering boxes!


1984 300D "Elsa" odo reset 6/2011 147k
1983 300TD "Mitzi" ~268k OM603 powered
1995 E300 "Adelheid" 262k [Sold]

Quite odd,

this oil is basically Dexron II ATF (made from a synthetic base) but dyed amber/yellow.

the same elusive stuff used as toyota PSF and has confused toyota owners since time immortal.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)