M4900, changed filters, no hydraulics!

[Roaddoggie]

I have an M4900 with 380 hours, and changed the two hydraulic filters today. The manual does not call for a change of fluid so I just pulled the filters and replaced them with Kubota filters, and lost about 4 gallons of UDT in the process. I replaced the UDT, checked the level and started and idled for five minutes, stopped and added a little more fluid, then started again, and found I have no hydraulics to the brushhog or front end loader. There are no leaks at the filters or anywhere else. Anybody have any idea what might be going on??

 

[Roaddoggie]

I have an M4900 with 380 hours, and changed the two hydraulic filters today. The manual does not call for a change of fluid so I just pulled the filters and replaced them with Kubota filters, and lost about 4 gallons of UDT in the process. I replaced the UDT, checked the level and started and idled for five minutes, stopped and added a little more fluid, then started again, and found I have no hydraulics to the brushhog or front end loader. There are no leaks at the filters or anywhere else. Anybody have any idea what might be going on??

Went out today and checked to see if the tractor had cured itself overnight. No such luck, but did notice that the power steering is not working either, which makes sense. Beginning to think I might have an air lock of some sort.....If I had a couple of clean buckets on hand I'd drain the 10 gallons of fluid and reinstall.

 

[kcender]

Have you tried turning the steering hard right and left multiple times with the tractor running?Seems I recall seeing somewhere on TBN that this will bleed the hydro system.By the way,welcome to TBN.

 

[Roaddoggie]

Thanks, I may try that tomorrow. It's 4-wd sitting on grass so may need to jack the front end up to get it to turn.

 

[Roaddoggie]

Talked to a dealer mechanic today, and he says it's definitely an air lock which he has seen before. His advice was to crack the pressure line coming off the hydraulic pump, pull the emergency stop, and crank the engine till I see fluid coming out. I think the pressure line is the one coming off the top back of the pump and going up under instrument panel. Anyone know for sure?

 

[crowhill]

Talked to a dealer mechanic today, and he says it's definitely an air lock which he has seen before. His advice was to crack the pressure line coming off the hydraulic pump, pull the emergency stop, and crank the engine till I see fluid coming out. I think the pressure line is the one coming off the top back of the pump and going up under instrument panel. Anyone know for sure?

did this work for you?

 

[Gator6x4]

How are you measuring the hydraulic fluid level? Is it possible you put the four gallons of fluid in the wrong place? Not questioning you or your ability, just trying to generate a thinking process. The filters should not cause a problem since they are new, unless the plastic across the top was left on and is now not allowing fluid to circulate. So that would leave the fluid not reaching the pump to allow for circulation.