hydroax problems

[forestbob]

Hey everyone. I have a hydroax 621B. had a total failure of both the hydraulic pumps. both the big pumps and the smaller auxiliary pumps attached to them were rebuilt and i put the machine back to work. in the month or so she has been back to work, I have blown a seal 4 times now between one of the hydraulic pumps and the aux. pump. it has been one of two seals. a shaft seal or a gasket that take turns blowing. I can get a week or so out of it and then it takes a ****. there is a weep hole in the bottom on the aux pump that oil will pour out of half the time it brakes. the other half it just comes spraying right between pump mating surfaces. I can not figure out why this is happening and neither can the guy who rebuilt my pumps. this project took place over several years and several people worked on the machine at different times. The only two things i can think of is someone along the way crossed a line and has pressure going were it shouldn't be, or a one way check valve is bad and back feeding pressure perhaps. when the pump comes back I am going to pressure test eveything and see if it tells me anything. Does anyone have any advise or technical reading material that may help? I have parts and operating books for the machine but there are discrepancies in the routing of all the hydraulics as the book is for a different model. I have some pressure testing numbers form the book to go off of but not many. Thanks again for any help you guys can give me!

[kiko]

Is this the pump on the top( drive pump) with the smaller steering pump on the back of it?  If you had a catastrophic pump failure it likely there is a piece of the old pump stuck in the case drain line. These pumps have internal leakage that is normal if the case drain is blocked ther is no where for the oil to go and it builds pressure in side the case and something's got to blow. I have seen this many times, it is best to just replace the case drain hose . I am familiar with hydro ax but not that particular model. If the hose is blocked you with find the blockage in a ninety degree fitting most of the time.

[bushmechanic]

Kiko is right on the money. To test the slippage of the oil in the pump you could do a case drain test to see if the problem may be the pump. You would have to tap into the case drain port on the pump though in case as kiko said the hose may be blocked. You really need the proper manual as things change rapidly from year to year.