Check with RKMACSERVICE for recently improved rebuild kits and new 2 piece stainless steel piston upgrades for the TRS21 Extraction/Recovery pump.
Most leaks come from two occurring events in the TRS21. One is the piston seals wear out, thus a direct leak through the unsealed crankcase. The second is rubber o-rings that are not properly size or the proper material being used.
they told me 700 hours but i didnt mention its use. I think we are harder on the pump due to no refrigerant lube. Ooops its their thread Ill let them answer. I bought a rebuilt pump from them directly just before I found future. It works.