Where is the best place to buy from and have people generally had success with them?

 

ebay...most people in america just replace the whole unit. in the UK though, many of these rebuild kits are available. platforms like the Land Rover are very popular for compressor rebuild.

https://www.ebay.com/itm/MERCEDES-E-CLASS-W211-AIR-SUSPENSION-COMPRESSOR-PISTON-SEAL-DRYER-REBUILD-KIT/152516773598?fits=Make%3AMercedes-Benz&hash=item2382b546de:g:FPEAAOSwB-1YuZXH&vxp=mtr

 

I just installed this kit last month, also available from Amazon. I did it proactively. I wasn't having any problems with the pump, I just wanted to check it out and hopefully avoid any problems in the future. I also replaced the filter and checked the condition of the drier.... which was dry. The pump works well. It was a little noisy at first, but had gotten much quieter as the new ring wears in.