Hydraulic leak at pump output

[Little_Grizzly]

I am new to solving hydraulic problems. Perhaps you folks could answer some questions?

1) When I remove the output flange from the high-pressure side of the pump it continually drips. In fact I found out it would have slowly drained my tank had I not stopped it. Is this normal? In other words, can (in a working pump) fluid leak from the suction side to the output side without the pump running? Or does it imply a bad pump?

2) I replaced the o-ring in the output flange and yet I still get a slow leak. I have not run the pump at all since I replaced the o-ring. Does it need to be run to "set" the o-ring or do I conclude that the o-ring isn't sealing properly already?

Thanks for any help you can give.

 

[J_J]

Did you use a factory o-ring or a generic o-ring, maybe a small difference.

There should be torque data for the bolts also.

 

[oldnslo]

I am new to solving hydraulic problems. Perhaps you folks could answer some questions?

1) When I remove the output flange from the high-pressure side of the pump it continually drips. In fact I found out it would have slowly drained my tank had I not stopped it. Is this normal? In other words, can (in a working pump) fluid leak from the suction side to the output side without the pump running? Or does it imply a bad pump?

Yes depending on the style of the pump and reservoir location fluid can seep through a pump.

2) I replaced the o-ring in the output flange and yet I still get a slow leak. I have not run the pump at all since I replaced the o-ring. Does it need to be run to "set" the o-ring or do I conclude that the o-ring isn't sealing properly already?

Thanks for any help you can give.

Did you use the correct size O-ring? If the O-ring is correct and there are no scratches on the sealing surface or foreign material between the surfaces the o-ring should seal.
Any scratches will prevent the seal from seating.

Dirt caught between the mating surfaces will also prevent the seal from being compressed properly and allow leaks.

 

[Little_Grizzly]

Thanks for the answers. The o-ring I used was 100 microns thicker in cross section. Most likely its the mating surface in the groove that is questionable. The face of the pump looks quite smooth and clean. The o-ring groove is dodgy. I will try and carefully clean it and retry fitting it.