I purchased one on eBay for my 64 230SL as I was told from the Prior Owner that his was stuck after 15 year storage.
The one I got had two pistons stuck, so I ended up taking it back off the car and following JA17's instructions about how to free up the pistons and the rack. Not terribly difficult, just a slow process.
Over time, I plan to work on my original pump later and free up the pump as they are pretty costly when you can find them. Prices which I have seen have ranged from $800 to several thousand. Definitely worth giving it a try to fix it yourself if its in reasonable condition.
For my 64 the plate number PES6KL70 / 120R11 11U03613
I am guessing that the 280SL would have a different pump, but not certain since its an early one.
Give it a try and see if you can get it pumping!!
John
