300SD Power Steering Pump Compatability
 

Just as an FYI, I replaced the power steering pump tonight on my '85 300SD. It was spewing fluid from the front seal by the pulley, causing a mess inside the engine bay and also on the outside of the car.

I was a bit concerned as the replacement ZF pump that I received, from an '82 300D, had 65 bar pressure as opposed to the 82 bar pressure pump on my car. It appears that the w123 pumps, while they fit perfectly, have different pressure than the w126 power steering pumps. To be sure, I took the car on a test drive tonight. I see no noticeable difference in the performance of either pump. Of course, the parts purists may hate this suggestion, but, if you are in a pinch, then this solution may work. I am sure there is a logical reason why Mercedes chose to engineer these differences in the pumps, but it escapes me. For me, paying $60 for the used part beats paying several hundred for a new one.

Brian

It will probably work fine, they might have just upped the pressure to increase steering ease when the car is sitting or something..... as you said it probably doesn't make much difference overall.

On a related note, I stopped by the dealer to see what they'd sell me a power steering return hose for ($35ish on Fastlane - dealer wanted $54 but as usual didn't have it in stock anyway) and on the diagram for the 300SD they showed me when trying to ID the right hose there was a whole convoluted cooling system. My return hose goes straight from the steering box back to the pump, but the diagram had it plumbed through a bunch of other crap before returning to the pump.

Anyone actually seen one of these on a 300SD? Why was it necessary? Did they just show me the wrong diagram? (Likely)

And while I'm at it, why is a simple three-foot length of hose so expensive, and would it be safe to substitute something else (say, fuel hose) with the same ID given that the return line is not under pressure?

the SD during the 617 era had a different steering box than the 123

What I cannot understand is why the dealer wants to force you buy a full meter of hose when you only need about half that amount. The hose is supplied in bulk; it's just as easy to cut off twenty inches as 39.

As I understand it, the decree came from corporate to make all sales of bulk hoses in meters, obviously because the manuals specify metric length. And to account for partial meters is too weird, its thinking Outside the Box, as corporate powers want to be all unified and at the same time they need to make a profit any way they can. Like selling more instead of less. The parts counters at the dealers are held to individual accounting.

Try buying the bypass hose that fits between the water pump and the thermostat housing, its all of about 3 inches long, so buying a meter of the stuff is crazy if your a individual that won't need any of the bypass hose in another hundred years.
That said, I have seen cars where the owners bought a length of non-layerd hose at a Poop Boys or JC Whitney or their local parts counter. A few years late the hose material has turned to mush if there is any diesel goop on it (100% the case on an old diesel!) and the hose starts leaking, meaning the job has to be done all over again usually at the new owners expense :mad::mad::mad::mad: and the possibility exists with the coolant bypass hose is the total loss of the engine if all the coolant is lost while driving :eek::eek:
German hose specifications are superior, they use hose that is built up in several layers then vulcanized somehow, its obvious when you examine it compared to conventional rubber hose. It definitely costs more to make, well maybe just a little more but its sold in far smaller quantities so after the USD is converted to Euros German hose is going to be a LOT more than a Gates hose.
The power steering return hose is also in that category of being a layered hose so I highly recommend buying whatever length it takes to do the job and you won't have to worry about it down the road.

For return line, u can slap in a Garden hose all u want is not going make any difference, cause it has little or no pressure. If u have $$ then buy from Merc dealers for $450 or whatever geinuine parts they give u.

Many yrs ago my 95 F 150, the return hose snapped, I went to Canadian tire the hardware section to buy a brass barb fitting, pushed her on, and she was good for 3-4 yrs anyways.

Pressure side u dont wanna to fool around, some under 1000 PSI.

Brian, there four part numbers for all the pumps that look similar to yours. Two are Vickers, two are ZF, two are 65 bar, two are 82 bar. The pump you took of your car must have been relpaced at some point, all 123's and early 107's call for a 65 bar pump, all 126's, 116's, (with the ex. of 6.9)and late 107's call for a 82 bar pump. Should be no problem mixing and matching any of them.

Chris