Easy fix. About $20 a pair from Home Depot. There should be some paint on the original ones that mark the strength. Get the same.

 

Okay, we can do better than stock...
we can add a protection to blow pressure out of vacuum line.

It is normally desirable for pp to have oil inside but it should not pump it out into the vacuum lines

Right now you vaccum pp is pumping oil out... we want to prevent that to preserve functionality.


> How To Vent Pressure...
-- Add a "T" branch to existing line with a second check-valve plummed to vent pressure out and hold vacuum in.
-- After that "blow out" branch, add you new in-line check valve to hold vacuum for existing accessories.

These two check-valves need to best be silicone to wistand 250°F hot oil duty.

FYI: when I got my cylinders to seal with better oiling, I got surprised by:
lower CC pressure improving my brake response!!!

 

There is a difference actually from a regular check valve to a membrane type stop/check valve.

Check valve usually has spring and some sort of ball as the valve. It takes more effort to un-seat the ball/valve, they call it the cracking pressure.
Membrane like found on the vacuum pump is the lightest easiest to deflect/move.

If you guys do snorkeling and have the snorkel with the membrane type water stop valve, that is very similar with the one used on the vacuum pump.

So if one is to get a check valve, get one with a membrane.

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Ha! The snorkel I had as a kid was S-shaped with a cage and ball on the top end that would keep water out when diving under the water.

(I can't even find a picture of one it is so old now.)

 

Here u go......