So I built a hydraulic pump today

[RCP57]

Thanks for the ideas guys. I did find a U cup seal on line in 1/8 so they are available. My local hydro shop didn't have any in stock that were 1/8 but said they could get them. They gave me the different O rings to try but didn't think they would work. I guess they were right. I guess I should make a new housing that has more meat on the back side. that would give me more room to install a proper seal. My Jung pump has a proper U cup seal but the shaft is larger too giving a lot more sealing surface. I'm wondering if the bushing in the motor is allowing the shaft to load one side of the O rings heavy when the pressure comes up. There always seems to be a little slack in these brushed motors but the original shaft length is long enough to use a support bearing on the other side. Maybe I should try that too? I put it back in the box and stuck it on the shelf because I was frustrated but I will get it on the bench again soon!

Reg