I'm replacing my AC pump, so of course I had to open her up and see what happened. First of all, it's pretty cool inside, I did not know that's how this pump was configured.

Anyway, I found a huge flat spot on the swash plate, maybe 2" long, with some gouge marks and sharp metal edges. I guess the hemispherical bushings found some minor defect and just started eating away at it.

Or is it supposed to be like that?

 

It's not Black Death, and it's not an AC Pump. It's a seized A/C Compressor.

Which came first, the chicken or the egg?

-- A piston starts to seize in its bore, overloading its "shoe" in compression in that phase. The shoe wear material, hard but brittle, fractures under the shock load, sending nasty abrasive grit into the cylinder bores. Then hard piston seizure(s), swash plate gets gouged and pinned to a stop, game over.

or

-- A shoe wear material breaks, or the material eventually wears down until the edge of the base-metal holder contacts the swash plate. Either way, shrapnel is generated, and with shoe material missing, the piston hammers away with the longitudinal play like a jack hammer, breaking more. Then one or more pistons seize in their bores, swash plate gets gouged and pinned to a stop, game over.

Note the thickness of the swash plate. Think of the forces transmitted from the swash plate through the small pivoting shoes to the pistons at, say, 350 PSI head pressure. And look at all the sliding surfaces! High loads, proper lubrication and cleanliness very important!

 

I think it was a bit of everything. I found a lot of teflon and black gunk in the orifice tube filter and in the pump, and you could see that the seals had been torn and dragged down the side of some pistons. Ragardless, it's working now!

I have about 40psi low side and 220psi high side. Does that sound right?