Got my o-rings in the mail today.
From what I had read in several sites, EPDM is the right material to use. Actually, like the rubber in the brake system, it is attacked by mineral oils.
I wonder if you may have access to metric stuff because of being around aircraft; I would not mind paying a few dollars for the right sized o-ring.
Did you get the right (metric) size? I do not know the effect of brake fluid on nitrile, but if the effect is swelling then they may work even better than the rings I chose (as long as they do not disintegrate or harden as rock)
I have checked them today; they do fit in the groove no problem. Also, they protrude above the surface of the valve body so I expect them to seal well.
EDIT: I forgot I had a photo (hope it shows the protrusion a little bit; it can be felt with a finger)
When I took the valves apart, they all have fluid in the middle section. Since I also removed the valves in each half, it seems there is no fluid flow between the halves except for some minimum amounts.
I have realized I need to take the valve completely apart and remove the valves from inside each half - some parts that were supposed to move were stuck. Apparently, contaminated brake fluid left rusty residue inside the proportioning valve locking it. Fortunately, I had long removed the old fluid and tons of rust from the front brake cylinders.
I'll do a how-to and post it in a new thread.
Thanks
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