M4900, changed filters, no hydraulics!

[Roaddoggie]

I posted this on TBN and didn't get much feedback, so I hope you guys can help me. BTW, the M4900 has been trouble free since new, and a great tractor, one of my best purchases ever.

I have an M4900 with 380 hours, and changed the two hydraulic filters. 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, front end loader, and power steering. There are no leaks at the filters or anywhere else. I talked to a dealer mechanic, 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? And does this procedure sound right?

 

[Newlyme]

Hi All,
Rather than start a new thread, I thought I would bring this one back from the dead.
I recently purchased an M4900 with 640 hours on it. I am doing the PM's myself and was reading through the threads here to see what others have done and ran across this issue Roaddoggie ran into. I am ready to do this service, fluid and filter change, and wondering if this is a common issue on start up.
Hoping for replies.
Thanks

 

[Newlyme]

Anyone got any thoughts?
I'm a mechanic by trade. Just looking for some friendly advice and experiences.
Thanks

 

[nickelplated5s]

If it's any help I did my L4740 last weekend, no problems. I was going to post for other first timers but never got around to it. The manual is a little misleading, there are drain plugs at each axle end. I would also recommend doing the front axle at the same time. For some reason it was a lot "dirtier." 5 gallon buckets with lids worked for me. I have friends who can burn it but most transfer stations take it for free.

 

[North Idaho Wolfman]

On Roaddoggie's issue, yes it can happen on some models, it happens when the bypass inside the pump becomes plugged (it's a very small port), it's not a very common problem.

Change fluid, filters and such and if you don't get pressure on the hydraulics right away, then, yes crack the high pressure output on the pump, pull the stop and crank till fluid flows, takes just a few seconds.

 

[Newlyme]

Thanks guys. Didn't anticipate any problems. I'll be changing tomorrow. Will update with results then.
nickelplated5s I did the front axle last weekend, no problems, oil coming out was very clean.
Thanks again guys these are my first Kubotas and am looking for those little tricks of the trade.

 

[Bulldog]

My first M9000 lost the steering when I changed the fluid, second 9000 didn't. Anyway, I called my dealer on the first one and they told me it was common and sometimes it would take 10 - 15 minutes at low idle for the hydraulics to start working again. They said just let it idle and work the steering back and forth a little and it would work the air out on it's on. It started working just like they said it would without any other issue.

 

[Newlyme]

Thanks Bulldog.
That's what I'm looking for everyone's experiences.

 

[Bulldog]

Thanks Bulldog.
That's what I'm looking for everyone's experiences.

I'll be honest with you, I about had a cow when mine didn't work. I was afraid something was wrong or that I did something wrong that had torn it up. When I called my dealer and said I had a problem. As soon as I said I just changed hyd oil he said you don't have steering do you. Just hearing that made me feel a lot better and then he explained everything.

This is one thing I love about OTT, we can all learn from each others experience good or bad.

 

[North Idaho Wolfman]

My L would loose 1/2 of it's hydraulic function (dual section pump) either when I did a hydraulic fluid change or when temps got down in the teens, had me worried that the pump was shot or that the regulator valve was going south.
I took the pump apart and found a crushed tiny bypass port O-ring and a bit of curd in the port.
Cleaned and replaced and have never had an issue since even when temps got down in the -20's.
So sometimes the littlest things can do it.

 

[Newlyme]

All done. Transmission fluid and filters changed. No issues.
Also changed the fuel filter. Bled the air. No issues.
All went smoothly.
Thanks for all of the replies.