I took some pics of the McMaster Carr Buna-N O-Rings , Buna-N back up washers , and the PTFE back up washers .
[color=green:a7f8249f29]9452K49 - Oil-Resistant Buna-N Multipurpose O-Ring, 3/16 Fractional Width, Dash Number 330, packs of 50 $11.82
5288T359 - Oil-Resistant Buna-N Backup Ring, 0.183" Wide, Dash Number 330, packs of 50 $8.93 pack
9560K86 - Extreme-Chemical PTFE Backup Ring, 0.183" Wide, Dash Number 330, packs of 10 $12.55[/color:a7f8249f29]
I don't see the need for the extreme back up washers , but some people may prefer the harder washer . The Buna-N back up washer stretched over the piston with no problem . The pics show the O-Ring and washer installed but they are not compressed so they are not perfectly centered .
One of my tractors that had a leather washer on an NAA style piston had it stuck under part of the O-Ring but was working with about a 15 minute leak down on the lift . I don't know if it was improperly installed or worked it's way under the O-Ring .
[color=green:a7f8249f29]9452K49 - Oil-Resistant Buna-N Multipurpose O-Ring, 3/16 Fractional Width, Dash Number 330, packs of 50 $11.82
5288T359 - Oil-Resistant Buna-N Backup Ring, 0.183" Wide, Dash Number 330, packs of 50 $8.93 pack
9560K86 - Extreme-Chemical PTFE Backup Ring, 0.183" Wide, Dash Number 330, packs of 10 $12.55[/color:a7f8249f29]
I don't see the need for the extreme back up washers , but some people may prefer the harder washer . The Buna-N back up washer stretched over the piston with no problem . The pics show the O-Ring and washer installed but they are not compressed so they are not perfectly centered .
One of my tractors that had a leather washer on an NAA style piston had it stuck under part of the O-Ring but was working with about a 15 minute leak down on the lift . I don't know if it was improperly installed or worked it's way under the O-Ring .