Mahidra 2555 HST power steering control valve leak.

[DirtHauler]

Thanks JerryK. I thought grabbing the steering wheel could be a problem, causing the leak. It's easy to do. I have a cab on my 2555 and there is no good place to grab as I get in and out, except for the steering wheel. I bought my tractor used and it was leaking when I purchased it. Apparently, the original owner must have grabbed the steering wheel quite often. Mahindra should design a grab bar so it could be installed by the owner, or at the factory. This would prevent people from grabbing the steering wheel. My leak gets worse the longer I drive the tractor. The oil warms up. I need to repair the unit or replace it. The TYM unit is the same as on my Mahindra 2555. The price the lady gave me was $840.00, a good $100.00 cheaper than the Mahindra dealer. The TYM dealer is checking with their TYM techs to see if there is a repair kit for the unit. I'm sure if I removed the unit, and disassembled it, I could locate seals.

Sounds like you found a good TYM dealer. When I called a "local" TYM parts dealer in regards to the HSU, they quoted me a price of $1,180.00. They didn't have one in stock, put me on hold and called the TYM warehouse, they didn't have one either and said it would take 3-6 weeks to get! So I called my Mahindra parts supplier and had it at my door in 3 days!
Now for the "rant", in regards to this "using the steering wheel as a grab bar" issue causing it to leak. How would one explain why the first HSU had to be replaced @ 136 hours? I have the 2555 shuttle "open cab" and the known issue with this series tractor is the excess temp of the hydraulic oil which is even more with an HST unit, this in turn "cooks" the seals & "O" rings to the point where they are no longer pliable and unable to seal properly when the oil is hot and thinner, I know this because I've had to replace numerous seals and "O" rings due to this. And I've had to replace the "sub shift" boot twice because it got brittle and split allowing oil to be slung out of the trans. My current issue: hydraulic oil leaking past the "seals" of the PTO input shaft (fly wheel end) and collecting/leaking out of the clutch housing..........should be a quick fix!..........right?

 

[TractorNH]

Take these two seals and go to a "good" bearing/hydraulic shop and match 'em up. They may or may not have the inner seal on hand as this is a "soft" seal (don't remember the technical name) but it can be gotten. Buy a few as you'll be doing this repair probably every 300 - 500 hrs. or plan on replacement of the HSU on roughly the same time frame

If anyone else ends up going this route can you post the manufacturer and part number of the replacement seals? This would be very helpful to others. I agree it seems totally foolish to have to buy a whole new valve to replace $15 worth of seals.

 

[RAHarden]

Sounds like you found a good TYM dealer. When I called a "local" TYM parts dealer in regards to the HSU, they quoted me a price of $1,180.00. They didn't have one in stock, put me on hold and called the TYM warehouse, they didn't have one either and said it would take 3-6 weeks to get! So I called my Mahindra parts supplier and had it at my door in 3 days!
Now for the "rant", in regards to this "using the steering wheel as a grab bar" issue causing it to leak. How would one explain why the first HSU had to be replaced @ 136 hours? I have the 2555 shuttle "open cab" and the known issue with this series tractor is the excess temp of the hydraulic oil which is even more with an HST unit, this in turn "cooks" the seals & "O" rings to the point where they are no longer pliable and unable to seal properly when the oil is hot and thinner, I know this because I've had to replace numerous seals and "O" rings due to this. And I've had to replace the "sub shift" boot twice because it got brittle and split allowing oil to be slung out of the trans. My current issue: hydraulic oil leaking past the "seals" of the PTO input shaft (fly wheel end) and collecting/leaking out of the clutch housing..........should be a quick fix!..........right?

Thanks for the info. I noticed a few weeks ago, how hot the loader cylinders were. I couldn't hold my hand on them. That concerned me. The Mahindra dealer mechanic said that was normal with these tractors, but he thought it was too extreme, at least compared to Case IH tractors, that they also sell and service. My brother owns a 3000 series JD hydro and he said the hydraulics never reach those high temps. It could be the type of rubber used in these seals. If Mahindra knows their hydraulic system runs at these high temps, the seals and O-rings should be designed to hold up to these temps. I worked at a nuclear generating plant as a maintenance mechanic. We installed many seals and O-rings in very high temp lines and hydraulic systems. These seals and O-rings were designed for the application. They held up well. Good point! My steering wheel shaft is not sloppy, in fact it doesn't have, maybe a few thousands side movement. Not much, if any.

As far as the TYM dealership and the price for a new unit goes. This is what she quoted and she said they had a new unit with the new part number. I asked if she had any idea what the difference was between the old and the new, she said no.

 

[RAHarden]

If anyone else ends up going this route can you post the manufacturer and part number of the replacement seals? This would be very helpful to others. I agree it seems totally foolish to have to buy a whole new valve to replace $15 worth of seals.

When I remove my unit and find seals or whatever it takes to rebuild the unit, I'll post all the info I can. I'm not sure when this happen, but it will be this month. Thanks

 

[RAHarden]

Rear Port Power Steering Unit drawings. I sent this and the pictures you people have posted, off to a seal company. Hopefully, they will come up with what we need.

View attachment eng_06RPPSU.pdf

 

[RAHarden]

I have the Sinjin PS unit apart. The case and covers are hard metal. Difficult to mark with a punch or awl. The unit only has two seals the are sealing the SW shaft. One is a quad ring or some call it an X-ring. The other is a dust seal. This seal has part numbers. I have both of them out and took as many measurements as I could. I will take good, detailed pictures of everything and post them. I was always told, a quad ring should not be used as a pressure seal, but that is what Sinjin used. The original quad ring has expanded or grown. It doesn't fit tight on the steering shaft. It also is thinner than the depth of the groove it fits into, which doesn't make sense. Who knows what the quad ring material is. There are other O-rings I'll replace as long as the unit is apart. These O-rings weren't leaking, but they seem hard. They are on the case and the hose fittings. I'll send everything off to that seal company I spoke with.

I took several measurements for the PS unit. The shaft measures .865" at the sealing surface. The cut out in the inner part of the main housing, where the quad ring fits into, measures 1.127" across and a depth of .149". The dust seal fit measures 1.177" across. I didn't measure the dust seal since it has size numbers. It did fit well. The quad ring measures .137" in height and from .125" to .135" thickness. The quad ring shows some wear on the shaft seal area and it has grown/expanded or it was too large to begin with. It does not fit the shaft, it's loose and it will not fit into the cut out inside the main housing, the seal is too large. There are three O-rings, all the same size, used in the housing, measuring .072" thickness, crushed. The grooves for theses O-rings measure 2.739" outer diameter and 2.555" inner diameter. These grooves where difficult to measure. There are four O-rings, all the same size, that fit into the hose fittings that are on the end cap that measure .065" thick, crushed. The grooves these O-rings fit into measures .430" outer diameter and .250" inner diameter. Also difficult to get an accurate reading. The only leak on the PS unit was at the shaft seal.

 

[RAHarden]

 

[RAHarden]

I just wanted to update everyone on the PSU seal leak. It looks like several other people have the same issue. I wanted a seal company to look at this and see if they had a better seal to install, other than a quad ring. They all agreed a quad ring was not their choice for the inner seal, but because of the built dimensions, they couldn't replace the quad ring with anything but the same, without getting into major changes. That would have cost me more than I wanted to spend and there was no guarantee the leak issue wouldn't return. The design flaw with the SINJIN PSU is, it doesn't have a steering shaft bearing for side load for side to side stability. The PSU has a roller thrust bearing, but that doesn't help side load. The seal engineers said this is a problem. SINJIN uses the quad ring as a stabilizer or bearing, to keep the steering shaft centered. Operating the steering causes side load on the quad ring, which causes wear. Just a poor design. Unless SINJIN redesigns this PSU, we are stuck with it and it's issues.
I ordered a new Viton #212 quad ring, an outer seal 22x30x5, three new Viton #038 O-rings and four new Viton #011 O-rings from The O-ring Store.com. The total cost was $26.52. I'll clean and reassemble, once the parts are here. Hopefully, I can repost good news with no leaks.

 

[DirtHauler]

........ The design flaw with the SINJIN PSU is, it doesn't have a steering shaft bearing for side load for side to side stability. The PSU has a roller thrust bearing, but that doesn't help side load. The seal engineers said this is a problem. SINJIN uses the quad ring as a stabilizer or bearing, to keep the steering shaft centered. Operating the steering causes side load on the quad ring, which causes wear. Just a poor design. Unless SINJIN redesigns this PSU, we are stuck with it and it's issues.

With that being said, you'd think them "rocket engineers" would just use a needle bearing, like the one pictured, on the shaft (this one is used on the PTO out-put shaft). But on the other hand, it's good to see you're still pursuing the "better mouse trap". Once you get it done and it fixes the issue, you may be able start your own little side business of repairing these and all the members who have the problem could just ship them to you for repair. Just don't let Mahindra or SINJIN catch wind of it or you could end up being sued for depriving them of profits!

 

[RAHarden]

With that being said, you'd think them "rocket engineers" would just use a needle bearing, like the one pictured, on the shaft (this one is used on the PTO out-put shaft). But on the other hand, it's good to see you're still pursuing the "better mouse trap". Once you get it done and it fixes the issue, you may be able start your own little side business of repairing these and all the members who have the problem could just ship them to you for repair. Just don't let Mahindra or SINJIN catch wind of it or you could end up being sued for depriving them of profits!

Thanks DirtHauler. I gave up on the seal redesign issue. It is what it is. I ordered new seals, but in Viton. I hope they last longer and don't leak. The PSU has a roller thrust bearing, but it only works for the end play of the spool. The spool is only held in place, centered, by the quad ring and the spool fit in the housing, which has clearance of several thousands. If there was a bearing, or even a bronze bushing for the steering shaft, I believe the side thrust, which comes from operating the tractor, would be almost eliminated. That would save the quad ring. The picture I sent, shows the roller thrust bearing.