Low Quality Aftermarket Spare Part

This very good looking and seemingly flawless copy of a valve plate for Rexroth A6VM motor is, actually, a useless piece of scrap since the curvature of the valve plate is not equal to that of the end plate!

To reveal the difference I marked the sealing surface and then rubbed the plate against the end plate - you can see that the only contact points are the extremities of the valve plate. Further measurements showed that in the middle of the valve plate the gap is 0.3 mm wide - meaning - internal leakage and lots of it!

It's easy to feel that the part is bad by moving it in its place - it "feels funny", the drag is not normal - it's too light. However, due to the fact that the part is well finished, a less experienced mechanic could easily mount this part without noticing that it's faulty.