Project tractor has brakes very slow to respond but they will lock it down when they do., steering only responds sometimes, between 800 rpm untill it hits about 1600rpm, then it looses steering and braking pressures. 3pt wont raise more than a couple inches. Hydraulic filter has been replaced, it wasnt bad. Charge pressure light does not come on when this happens. hydraulic filter and tube are clean and tight. pulled servo and unloader valve and everything looked good there as well. splines on PTO shafts and clutch hub are good. Hoping someone can guide me in the right direction, Id love to get this thing out of my shop and into the fields.
- Thread starter KShow
- Start date
The 2-135 had a hydraulic system a little different than the 85 and 105, but still similar in essentials: A Vickers PVB or PVE (depending on serial number) closed-centre (variable-displacement) pump feeding a pressure valve assembly (consisting of relief, unloader, and priority valves). They were the weak point of any of that series of tractors. The pumps often get worn out, start bypassing, and cause all sorts of grief. There's a lot of Whites parked in fence rows or sent to scrappers because of hydraulic issues.
Luckily, even with a worn-out pump, you can usually do some cobbling to get it functioning again. Lots of folks will do a case drain test on the pump, find out its worn, and assume that's the main problem and the tractor's junk (the cost of a new pump is often more than the tractor's worth). But even when one of these pumps is old and worn, that's often not the real problem. The pressure valve assemblies are often the real culprit: The o-rings inside them will get degraded/perished, the spools will get sticky (it only takes a tiny bit of crapulence to cause one of the spools to stick), and when this happens it will cause all sorts of grief. The priority valve is what ensures steering and brakes take priority of flow over the rest of the hydraulics, while reducing valve knocks down the pressure to the brake system. You say you did the servo and unloader valves. but I'd guess that you have a priority valve issue: I had issues with it on my 105 (which has the same priority valve). I still have some brake misbehaving issues (low flow to remotes when operating brakes), but I'm pretty sure that's the unloader valve, which I haven't yet taken apart. And it's way better than it used to be (I was having issues similar to yours)
I did my compensator and priority valves without removing the assembly from the tractor - just because I was in a rush and needed to get baling.
Take a look at the link below (parts book for the 135 & 155), go to page 208 (showing details of the pressure control valve). Items 23 and 29 and the various spools/components beneath them are what I'd start with. Take them apart, clean up, make sure they're shifting and not binding, re-seal with new o-rings, put back together, and see what happens. You might have trouble getting items 14 and 25 out, but if I remember right, there are threads in the end of each you can thread a bolt into and use to pull them out. I confess I had such trouble with the priority valve (item 18) on one of mine that was really stuck that I removed al the components in front of it, had someone hold a bucket in front of it, then fired up the tractor for a second. The pressure when running shot the priority valve plug out into the bucket. The o-rings on it were the main problem on mine (similar symptoms to yours). You can get the o-rings at any Napa or industrial supply: The Agco parts book lists the o-ring cross-section and I.D., tehn you just have to google SAE o-ring sizes and see what standard SAE o-ring corresponds to the ones you need.
Also critical to ensure the relief valve is functioning properly: The relief valve pressure is set with shims under the main spring (item 21). Over time, the shims get hammered out and the relief pressure drops. If it drops below what the compensator pressure is set at, it will always be blowing by the relief, creating excess heat and burning up the pump (and seals). In general, you want the relief valve set at least 200 PSI above the compensator pressure setting.
Luckily, even with a worn-out pump, you can usually do some cobbling to get it functioning again. Lots of folks will do a case drain test on the pump, find out its worn, and assume that's the main problem and the tractor's junk (the cost of a new pump is often more than the tractor's worth). But even when one of these pumps is old and worn, that's often not the real problem. The pressure valve assemblies are often the real culprit: The o-rings inside them will get degraded/perished, the spools will get sticky (it only takes a tiny bit of crapulence to cause one of the spools to stick), and when this happens it will cause all sorts of grief. The priority valve is what ensures steering and brakes take priority of flow over the rest of the hydraulics, while reducing valve knocks down the pressure to the brake system. You say you did the servo and unloader valves. but I'd guess that you have a priority valve issue: I had issues with it on my 105 (which has the same priority valve). I still have some brake misbehaving issues (low flow to remotes when operating brakes), but I'm pretty sure that's the unloader valve, which I haven't yet taken apart. And it's way better than it used to be (I was having issues similar to yours)
I did my compensator and priority valves without removing the assembly from the tractor - just because I was in a rush and needed to get baling.
Take a look at the link below (parts book for the 135 & 155), go to page 208 (showing details of the pressure control valve). Items 23 and 29 and the various spools/components beneath them are what I'd start with. Take them apart, clean up, make sure they're shifting and not binding, re-seal with new o-rings, put back together, and see what happens. You might have trouble getting items 14 and 25 out, but if I remember right, there are threads in the end of each you can thread a bolt into and use to pull them out. I confess I had such trouble with the priority valve (item 18) on one of mine that was really stuck that I removed al the components in front of it, had someone hold a bucket in front of it, then fired up the tractor for a second. The pressure when running shot the priority valve plug out into the bucket. The o-rings on it were the main problem on mine (similar symptoms to yours). You can get the o-rings at any Napa or industrial supply: The Agco parts book lists the o-ring cross-section and I.D., tehn you just have to google SAE o-ring sizes and see what standard SAE o-ring corresponds to the ones you need.
Also critical to ensure the relief valve is functioning properly: The relief valve pressure is set with shims under the main spring (item 21). Over time, the shims get hammered out and the relief pressure drops. If it drops below what the compensator pressure is set at, it will always be blowing by the relief, creating excess heat and burning up the pump (and seals). In general, you want the relief valve set at least 200 PSI above the compensator pressure setting.
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Still fighting the issue, have had pressure valve apart and everything seems to be moving freely. Hooked gauges to it and it will build up to 1100-1300psi as you raise the throttle. Once you pass 1500rpm, the pressure instantly drops to almost 0. Charge pressure light does not come on anytime the engine is running so I dont think its a charge pump issue, new filter as well. I do hear some chatter that sounds like its coming from the main pump. Ive been searching through the shop manual and havent been able to find much help
paulsamwel
Member
Did you do the case drain test as suggested above?
Hmm, that still seems like a priority valve or compensator problem. Did you have all spools out right down to the deepest depths? I think there are three spools to come apart, some of which have several minor components inside you really have to get creative with to get out. A case drain test is also a good idea, but if you're building pressure at low RPM I'd be surprised if that was you issue (it could still be an issue, but wouldn't cause the symptoms you're talking about).
At higher RPM you have almost no pressure, but do you have any flow? That would perhaps be worth finding out. Maybe even something as simple as a line from a remote leading into a bucket, and checking what happens when you shift that remote at high RPM. Perhaps something could be awry with the compensator valve (which is on the pump, not part of the pressure valve) and thus the pump's destroking at higher RPM for some reason. The compensator spool is pretty easy to take out with it on the tractor if I remember correctly. The first pic below is the compensator paraphernalia for a 2-135. I can't really picture why it would change with RPM, but stranger things have happened.
I strongly suspect either compensator or priority valve, and from your initial description in your first post I'm still leaning towards priority. But that is admittedly just a guess. The second picture shows the priority valve paraphernalia. Note that you really have to dig deep to get the inner parts out of the priority valve. If you were doing it in-place on the tractor, perhaps you got the stuff circled in blue apart, but not the stuff in green (which is the really critical part of the priority valve, and a real pain to get #18 out)
At higher RPM you have almost no pressure, but do you have any flow? That would perhaps be worth finding out. Maybe even something as simple as a line from a remote leading into a bucket, and checking what happens when you shift that remote at high RPM. Perhaps something could be awry with the compensator valve (which is on the pump, not part of the pressure valve) and thus the pump's destroking at higher RPM for some reason. The compensator spool is pretty easy to take out with it on the tractor if I remember correctly. The first pic below is the compensator paraphernalia for a 2-135. I can't really picture why it would change with RPM, but stranger things have happened.
I strongly suspect either compensator or priority valve, and from your initial description in your first post I'm still leaning towards priority. But that is admittedly just a guess. The second picture shows the priority valve paraphernalia. Note that you really have to dig deep to get the inner parts out of the priority valve. If you were doing it in-place on the tractor, perhaps you got the stuff circled in blue apart, but not the stuff in green (which is the really critical part of the priority valve, and a real pain to get #18 out)
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I picked up a couple necessary O-rings on the way home from work today. I have replaced ALL internal O-rings on the pressure valve assembly (there are no external leaks). Ran the machine and was able to reach 1500+ psi in the beginning, then it dropped out, and I could only bring it up to 1100psi before it would drop instantly to 0 on the gauge. I rechecked fluid level and it was good, but fluid looked a bit foamy. Fired it up and brought pressure to 1000psi and pulled the dipstick for the hydraulic/rear end, it was very foamy and turbulent. Soooo......
One of the scenarios running through my head is that the charge pump must be sucking air somewhere inside the transmission. I "thought" everything looked good when I had it opened but it looks like I was wrong. Looks like I'll be pulling the cab off again to gain access to the transmission. This tractor is a 1978 so it doesn't have the large floor opening, and honestly, I can have the cab off in about an hour by myself. Then I'll have much better access than expanding my floor hatch, which would be better to do with the cab off anyways.
After a bit more thought, I think I'll drop the hydraulic oil, then try to pull and replace the O-ring on the pickup tube. If that doesn't do it, then the cab comes off. It was tight when I checked it before, but after seeing the condition of some of the O-rings I've replaced, it probably wouldn't hurt to do that one before I dig deeper.
I appreciate everyone's advice and I will keep this thread updated with what happens next on this "winter project" that's approaching its third winter...
One of the scenarios running through my head is that the charge pump must be sucking air somewhere inside the transmission. I "thought" everything looked good when I had it opened but it looks like I was wrong. Looks like I'll be pulling the cab off again to gain access to the transmission. This tractor is a 1978 so it doesn't have the large floor opening, and honestly, I can have the cab off in about an hour by myself. Then I'll have much better access than expanding my floor hatch, which would be better to do with the cab off anyways.
After a bit more thought, I think I'll drop the hydraulic oil, then try to pull and replace the O-ring on the pickup tube. If that doesn't do it, then the cab comes off. It was tight when I checked it before, but after seeing the condition of some of the O-rings I've replaced, it probably wouldn't hurt to do that one before I dig deeper.
I appreciate everyone's advice and I will keep this thread updated with what happens next on this "winter project" that's approaching its third winter...
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