Dirtleg
Member
I will first confess that the extent of my hydraulic knowledge is centered around rotary gear pumps used in the chemical industry and the things I've learned fooling with my MF 135 tractors' steering system. Let me first apologize for the length of this post but it's been a long saga that leads me here for opinions.
So I bought my MF 135 Orchard about a year ago. After about 20 hrs of use the seal on the steering shaft blew out. This continued to happen and I was so busy at work that I just took it to the MF dealer in October to diagnose and fix. Long story they just replaced the seal without any diagnostic work, charged me $500 and sent it back. The seal blew in 2 hours of use. I let them know how I felt about their service and left it at that.
I continued to work way too much and let it sit for another 2 months. The new service manager at the MF dealer calls me and says he's going over some unresolved customer complaints and came across mine. We discuss the issues and he offers to actually diagnose the problem and credit me the whole first bill. So I agree to let them try again. Big props to this guy.
After 4 weeks and another 4 blown seals at the dealership they think they might have it fixed. Total new bill $65. Not bad as I know they really tried to fix it right. He also tells me they really don't have a solid idea why it was happening but they lowered the pump pressure and didn't blow any more seals so they just basically said we're crossing our fingers and hope it works but if it doesn't we're out of ideas. Not really confidence inspiring but I appreciated the honesty.
Seals keep blowing however and I am looking at the steering system closer and closer trying to see what could be wrong. On the 135 orchard the power assist piston is replaced by 2 hydraulic cylinders on the front axle. The 2 on my tractor were not identical to each other and due to length issues it would not turn all the way to the right. My theory was that it was bottoming out when turning right and backfeeding through the orbital valve thus overpressurizing the seal. Through some creative cylinder modifications I was able to shorten the mounts for the too long cylinder enough to make it really close in length to the other one. I still blew the seal.
My next step was to completely disassemble the orbital valve and steering gear to check for anything unusual. The only thing I found that caught my attention was that the ball and check assemblies that my manual shows are different than what I have. Mine are a straight through port without an actual check ball. Interesting.
I put it back together and went to flush the system. So looking in the manual I disconnected the return line from the PS pump and put it in a bucket. When I cranked the tractor over fluid shot out of the pump not the return line. Hmm. So now for the first time I actually did a complete analysis of the hydraulic line routing on my tractor. I discovered that whoever had redone it before (2 owners ago) had completely hooked up the hydraulic steering flow backwards. This would explain why the seal was blowing IMO. I put it back together Sunday and had to fly to California today (monday) so it's as of now untested.
So my question after all that is; can my orbital valve be designed without check balls? If so can anyone explain how it works?
Thanks.
So I bought my MF 135 Orchard about a year ago. After about 20 hrs of use the seal on the steering shaft blew out. This continued to happen and I was so busy at work that I just took it to the MF dealer in October to diagnose and fix. Long story they just replaced the seal without any diagnostic work, charged me $500 and sent it back. The seal blew in 2 hours of use. I let them know how I felt about their service and left it at that.
I continued to work way too much and let it sit for another 2 months. The new service manager at the MF dealer calls me and says he's going over some unresolved customer complaints and came across mine. We discuss the issues and he offers to actually diagnose the problem and credit me the whole first bill. So I agree to let them try again. Big props to this guy.
After 4 weeks and another 4 blown seals at the dealership they think they might have it fixed. Total new bill $65. Not bad as I know they really tried to fix it right. He also tells me they really don't have a solid idea why it was happening but they lowered the pump pressure and didn't blow any more seals so they just basically said we're crossing our fingers and hope it works but if it doesn't we're out of ideas. Not really confidence inspiring but I appreciated the honesty.
Seals keep blowing however and I am looking at the steering system closer and closer trying to see what could be wrong. On the 135 orchard the power assist piston is replaced by 2 hydraulic cylinders on the front axle. The 2 on my tractor were not identical to each other and due to length issues it would not turn all the way to the right. My theory was that it was bottoming out when turning right and backfeeding through the orbital valve thus overpressurizing the seal. Through some creative cylinder modifications I was able to shorten the mounts for the too long cylinder enough to make it really close in length to the other one. I still blew the seal.
My next step was to completely disassemble the orbital valve and steering gear to check for anything unusual. The only thing I found that caught my attention was that the ball and check assemblies that my manual shows are different than what I have. Mine are a straight through port without an actual check ball. Interesting.
I put it back together and went to flush the system. So looking in the manual I disconnected the return line from the PS pump and put it in a bucket. When I cranked the tractor over fluid shot out of the pump not the return line. Hmm. So now for the first time I actually did a complete analysis of the hydraulic line routing on my tractor. I discovered that whoever had redone it before (2 owners ago) had completely hooked up the hydraulic steering flow backwards. This would explain why the seal was blowing IMO. I put it back together Sunday and had to fly to California today (monday) so it's as of now untested.
So my question after all that is; can my orbital valve be designed without check balls? If so can anyone explain how it works?
Thanks.
