Pump seal

[bottleworks]

I have been trying to find the source of air getting sucked into the suction side of my backhoe's hydraulic pump. I have redone the entire suction lines. At this point, I suspect it is being pulled past the pump's shaft seal. In a typical gear pump, is the shaft seal subjected to the low pressure side or the high pressure side? Am I far off base?

 

[Wayne County Hose]

I would suspect a cracked body before a seal. Usually those seals will leak fluid out, not air in. Double and triple check everything on the suction side. Try replacing or removing the screen. I have seen screens that look clean still cause a problem. Left it out, problem solved. Take nothing for granted.

To answer your question, yes and no. Look at the pump breakdown. The teeth on the backside that you can't see are on the low pressure side, the teeth facing you are on the high pressure side. Fluid is grabbed from the backside, rotated around towards you, and forced to the outlet because it can't go back between where the gears mesh. Make sense?

 

[bottleworks]

I Follow you. I will take a look at the two o-rings for the main body.