Looking for a seal kit for my Kubota M4050 power steering cylinder. They also call it a booster. I have tried Messicks and they do not list anything.
Power Steering rebuild kit
- Thread starter Whitetail Hunter
- Start date
@Whitetail Hunter Welcome to the forum.
From part numbers looks to be the same booster used on other older Kubotas like the M4500DT so a few people including me would be interested in how you solve this. 2 thoughts:
1. Someone else at OTT posted that they overhauled one almost certainly like yours in the last few months I think, may be this year. Shouldn't be too hard to shake the tree and get them to let you know what they did.
2. Would you be willing to write up the job you do on it, including seal part numbers or sizes?
From part numbers looks to be the same booster used on other older Kubotas like the M4500DT so a few people including me would be interested in how you solve this. 2 thoughts:
1. Someone else at OTT posted that they overhauled one almost certainly like yours in the last few months I think, may be this year. Shouldn't be too hard to shake the tree and get them to let you know what they did.
2. Would you be willing to write up the job you do on it, including seal part numbers or sizes?
Sorry I just saw this. As of yet, I have not been able to shut the tractor down long enough to pull it apart. Once I do, I will forward seal numbers, etc. I have just been adding fluid ever so often.
Its just an old school hydraulic assist cylinder/valve. Hydraulic shops see these things all the time. .Take it off, drop it off, and put it back on.
Messicks lists all the seals individually. I don't see anything special about them - orings, u-cups, and backup rings. As usual Kubota prices are insanely high - e.g. $9 for a $.05 o-ring.
Dan
@Whitetail Hunter, I agree with @TheOldHokie, all true.
However, great timing! I recently did mine (M4500DT) so if you really want to DIY, as he says, it's not hard. Edit: photos added.
The WSM is reasonable but the following additional info could help. Mine was working fine, but I got stuck into it becuz it was oily/messy, the ball stud boot was torn and the wiper seal looked askew.
On-line parts listing: the only detailed parts breakdown of the booster available on-line AFAIK is in the M4050DT (hydraulic section) even though the same booster is used in all the M500 series tractors. (The M4500DT online parts list ignores the power steering and booster completely; my hard copy parts book lists it but not the relief valve parts...).
Available parts from Kubota include: O-rings, ball stud dust seal, and rod seal. I thought that it would probably save time to get the OEM dust seal and rod seal, and so I decided to buy the OEM O-rings at the same time.
Unavailable include: ball joint boots and rod wiper. Ball joint dimension table is below. Wiper seal: standard 32mm OD x 22mm ID x 6 or 7mm thick, available from most seal or hydraulic shops. (Apologies regarding an earlier post, I didn’t realise that there was a large chamfer lead-in and I had measured that. [embarrassing]).
Terminology: what Kubota calls ‘the box’ is the gland or cylinder head assy housing the rod seal and the wiper seal. (‘Box’ derived from ye olde quaint steam system ‘piston rod or valve stem stuffing box’?)
Tools: usual metric plus 50mm C spanner, 36mm A/F open-ended spanner. M14x1.5 and M16x1.5 taps and die nuts if cleaning up ball joint threads.
Stripping and assembly
Spool: tricky… this looks perfectly symmetrical end-for-end but there are fractions of a mm difference and apparently getting it wrong is baaaad. Not mentioned in the manual, there is a small groove machined around one end of the spool, and that end goes closest to the shifter housing (where the ball stud is).
Relief valve stem O-ring: tiny (2mm ID) and buried inside the adjuster body. Removal not referred to in the WSM. I decided to not to replace that because it just seemed to difficult/risky and there was a reasonable drag on the stem which probably meant it was sealing OK anyway. The adjuster body seems to have been made in 2 pieces to manufacture the O-ring groove (and install the O ring?), then permanently swaged together. Does anyone have a foolproof way of removing and replacing such a small O-ring about 8mm down inside a 2.3? mm dia hole?
Shifter housing snap ring: the snap ring is shaped so a leg engages in a hole inside the sleeve. It wasn’t easy to get out and even trickier to get back in. Marking the visible end of the sleeve with the orientation of the hole helped a lot.
Hydraulic hose fittings/threads: hose fittings are all 3/8” BSP 45 degree cone type. Replacement 3/8” hose: I settled for SAE 100R1 because the more flexible R17 wasn’t available. Hard lines to the PS tank are M18x1.5 JIS flare, 22mm A/F.
(Relief valve pressure 9.8MPa/98 bar/1422 psi = less than the hitch hydraulic system.)
Ball joints/boots/dust covers: Probably same as used on 1970s Japanese 4WDs or light trucks of the 1970s so someone who knows their 50 y.o. Jap vehicles may be able to come up with part numbers. Also could try some European vehicles of same vintage. Or the dimensions below may help for aftermarket sourcing.
The original Kubota ball joint boots had a steel ring bonded into the rubber in the small end (not visible but can be felt) and a swaged ring at the large end.
I got cheap universal fitment boots from Aliexpress rather than the same boots from aftermarket suppliers (judging by the photos). Others have found that these don't last well, so this will confirm or otherwise
Ball stud/shifter housing dust boot: if not available locally could be made up from ball joint dust boot and flat square as per dimensions below.
Installation
Random addition: Vickers S20
The Kubota boosters are very similar to Vickers S20, maybe Kubota made them under licence or vice-versa. There’s very little info about the S20 on the ‘net, so anyone rebuilding an S20/S22 might find the Kubota M500 series WSM ‘how it works’ section helpful.
The end
That’s all there was to it. As as always, constructive criticism welcome.
However, great timing! I recently did mine (M4500DT) so if you really want to DIY, as he says, it's not hard. Edit: photos added.
The WSM is reasonable but the following additional info could help. Mine was working fine, but I got stuck into it becuz it was oily/messy, the ball stud boot was torn and the wiper seal looked askew.
On-line parts listing: the only detailed parts breakdown of the booster available on-line AFAIK is in the M4050DT (hydraulic section) even though the same booster is used in all the M500 series tractors. (The M4500DT online parts list ignores the power steering and booster completely; my hard copy parts book lists it but not the relief valve parts...).
Available parts from Kubota include: O-rings, ball stud dust seal, and rod seal. I thought that it would probably save time to get the OEM dust seal and rod seal, and so I decided to buy the OEM O-rings at the same time.
Unavailable include: ball joint boots and rod wiper. Ball joint dimension table is below. Wiper seal: standard 32mm OD x 22mm ID x 6 or 7mm thick, available from most seal or hydraulic shops. (Apologies regarding an earlier post, I didn’t realise that there was a large chamfer lead-in and I had measured that. [embarrassing]).
Terminology: what Kubota calls ‘the box’ is the gland or cylinder head assy housing the rod seal and the wiper seal. (‘Box’ derived from ye olde quaint steam system ‘piston rod or valve stem stuffing box’?)
Tools: usual metric plus 50mm C spanner, 36mm A/F open-ended spanner. M14x1.5 and M16x1.5 taps and die nuts if cleaning up ball joint threads.
Stripping and assembly
Spool: tricky… this looks perfectly symmetrical end-for-end but there are fractions of a mm difference and apparently getting it wrong is baaaad. Not mentioned in the manual, there is a small groove machined around one end of the spool, and that end goes closest to the shifter housing (where the ball stud is).
Relief valve stem O-ring: tiny (2mm ID) and buried inside the adjuster body. Removal not referred to in the WSM. I decided to not to replace that because it just seemed to difficult/risky and there was a reasonable drag on the stem which probably meant it was sealing OK anyway. The adjuster body seems to have been made in 2 pieces to manufacture the O-ring groove (and install the O ring?), then permanently swaged together. Does anyone have a foolproof way of removing and replacing such a small O-ring about 8mm down inside a 2.3? mm dia hole?
Shifter housing snap ring: the snap ring is shaped so a leg engages in a hole inside the sleeve. It wasn’t easy to get out and even trickier to get back in. Marking the visible end of the sleeve with the orientation of the hole helped a lot.
Hydraulic hose fittings/threads: hose fittings are all 3/8” BSP 45 degree cone type. Replacement 3/8” hose: I settled for SAE 100R1 because the more flexible R17 wasn’t available. Hard lines to the PS tank are M18x1.5 JIS flare, 22mm A/F.
(Relief valve pressure 9.8MPa/98 bar/1422 psi = less than the hitch hydraulic system.)
Ball joints/boots/dust covers: Probably same as used on 1970s Japanese 4WDs or light trucks of the 1970s so someone who knows their 50 y.o. Jap vehicles may be able to come up with part numbers. Also could try some European vehicles of same vintage. Or the dimensions below may help for aftermarket sourcing.
The original Kubota ball joint boots had a steel ring bonded into the rubber in the small end (not visible but can be felt) and a swaged ring at the large end.
I got cheap universal fitment boots from Aliexpress rather than the same boots from aftermarket suppliers (judging by the photos). Others have found that these don't last well, so this will confirm or otherwise
Ball stud/shifter housing dust boot: if not available locally could be made up from ball joint dust boot and flat square as per dimensions below.
Installation
- Original oil spec is Turbine oil ISO VG 32 or equivalent. I checked around including Kubota and they said OK to use SUDT or equivalent. One of the manuals says it takes 2l of oil, but that’s probably for oil change, fill from empty takes [TBA] litres.
- Zerk in ball stud housing needs to be removed to adjust the relief valve pressure. I wouldn’t normally comment on this mundane detail but it was done up so tight the entire Kubota sumo wrestling team must have got together on a really long strong bar to tighten it. I worried about snapping it off when trying to undo it. Fortunately it didn’t break but it must have been close.
Random addition: Vickers S20
The Kubota boosters are very similar to Vickers S20, maybe Kubota made them under licence or vice-versa. There’s very little info about the S20 on the ‘net, so anyone rebuilding an S20/S22 might find the Kubota M500 series WSM ‘how it works’ section helpful.
The end
That’s all there was to it. As as always, constructive criticism welcome.
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