The 6 cylinder W126s had the W124 style tandem pump.

There are two ways to do hyro boost power brakes. I'll call them the Ford way and the Audi way. The Ford way has the brake booster work like a power steering rack... when there is no assist called for the booster lets all the pressure return to the pump, just like the steering rack, so when there is no assist needed the pump doesn't work that hard. On an Audi the booster only lets fluid back when you release the pedal. There is an accumulator with a pressure relief valve that goes back to the pump. The pump charges the accumulator... the result is you get about 20 pedal presses with assistance after the engine is shut off. On the Ford when the engine stops the assist goes with it.

If you wanted to convert to the W124 style tandem power steering pump I'd think it could work ok. But I'd think it would be easier to get another pump from a 560, considering they all have one.

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

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