"Richard Smith" wrote in message ...

"Jim Wilkins" writes:

"Richard Smith" wrote in message
...


...

Does the pump have some mechanism to throw out air in the system?
Is it "self-bleeding"?

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Oil released from the cylinder to retract the piston flows back into
the pump's reservoir, which needs to be vented to the atmosphere to
relieve pressure or vacuum as oil moves in and out. I have a hand/foot
powered manual hydraulic pump with a hex head reservoir fill and
bleeder screw that the instructions say to slightly open during use.

Ah... The oil separates to the top in the pump's oil reservoir and
can be expelled / displaced with additional oil...

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I just finished reading this book;
https://www.amazon.com/Secret-Horsep.../dp/1911658506
The author is a racing engineer familiar with the technical difficulties of
high horsepower engines which he describes in detail, such as the problem of
separating the highly agitated oil and air froth that comes back from the
scavenger pumps in the dry sump Merlin, so that air bubbles won't be pumped
into highly loaded crankshaft bearings which would allow them to rub and
wear rapidly. The problem is worse in a fighter where "down" can be in any
direction.