Could someone explain to me how the hydraulic lift compensators work (HLC)? I'm considering replacing a few or all of mine on a 1989 420 SEL. I have a few really slow moving HLCs and I think they maybe filled with sludge.

As I remove a HLC, I find sludge in the bottom of the main HLC hole. Is there a small oil inlet hole somewhere in the bottom of the main cavity where the HLC is screwed into? I see a small oil inlet hole at the top of the main HLC cavity, but is there one at the bottom too?

Also, what happens if the thrust washer is too big? Does it prevent the valve from closing completely?

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1989 420 SEL