Welp, baptized my PT-425 today.

   / Welp, baptized my PT-425 today. #11  
What happens when your accumulator wears out?

I would recommend putting a wrench on everything you could get to easily. Then determine if you want to do the harder stuff by how much you find loose (seat bolts, cooler bolts, wheel lug nuts, etc). Of course you have to check the center pin as regular maintenance.

Years ago I bought a new Kubota B7100 and when I went through checking it over, I found the steering box dry. Nothing was loose, just nobody put any oil in it. Would have made for nice steering in the years to come.
The accumulator has a charging valve with an external spring that controls the flow of oil into the brake circuit, and diverts the excess oil once the internal pressure is above 600-1,000psi (I don't know exactly what pressure Power-Trac has it set at.) So the spring cycles the valve in and out, while being exposed to external dust. Eventually, the seals on the charging valve are what wear out.

The last time I replaced the charge valve/accumulator, Terry seemed to be of the opinion that I had an internal leak somewhere (perhaps in the brake system) that was draining off the pressure, but couldn't really suggest a next step, as it was also possible the most recent charge valve had an internal issue. The jury is still out. The symptom is that the charging valve cycles way too frequently, as in every twelve seconds.

All the best,

Peter
 
   / Welp, baptized my PT-425 today.
  • Thread Starter
#12  
Used the machine for a couple of service meter hours today and no sign of other gremlins so far.

Because the leak was up front by the time the oil leaked down the hose and into the footwell it was relatively cool (or at least enough I didn't get burned). For cleanup I did pull the two side panels down by my feet and wiped up the oil I found there, then washed the affected areas down with Simple Green. That way, if more oil ever appears I know it's new and not leftover from this incident.

Checked the fluid level and that seems about as full as when it was new, so although it SEEMED like a lot of oil to me (my new machine! 😱) it didn't amount to a whole lot.
 
   / Welp, baptized my PT-425 today.
  • Thread Starter
#13  
What happens when your accumulator wears out?

I would recommend putting a wrench on everything you could get to easily. Then determine if you want to do the harder stuff by how much you find loose (seat bolts, cooler bolts, wheel lug nuts, etc). Of course you have to check the center pin as regular maintenance.

Years ago I bought a new Kubota B7100 and when I went through checking it over, I found the steering box dry. Nothing was loose, just nobody put any oil in it. Would have made for nice steering in the years to come.
We're both thinking the same thing. I checked all the connectors in that "cluster" up front just to be sure it wasn't a missed assembly step. There was only the one that was loose. I WAS working the 3rd function a lot with the hoe, so I probably did cycle it a lot more than usual that day.

Hey on that center pin, I see the grease zircs and was planning to give them a squirt at the 50 hour service. Do they need it more often than that? I've been watching the other linkage pins and those seem pretty good to go. 12 hours on it today.
 
   / Welp, baptized my PT-425 today. #14  
All the grease points are every 8 hours, per my manual, and Terry. I doubt that yours is different. (I could be wrong, of course.)

All the best,

Peter
 
   / Welp, baptized my PT-425 today.
  • Thread Starter
#15  
Very good Peter - we'll hit 'em next time by!
 
   / Welp, baptized my PT-425 today. #17  
The accumulator has a charging valve with an external spring that controls the flow of oil into the brake circuit, and diverts the excess oil once the internal pressure is above 600-1,000psi (I don't know exactly what pressure Power-Trac has it set at.) So the spring cycles the valve in and out, while being exposed to external dust. Eventually, the seals on the charging valve are what wear out.

The last time I replaced the charge valve/accumulator, Terry seemed to be of the opinion that I had an internal leak somewhere (perhaps in the brake system) that was draining off the pressure, but couldn't really suggest a next step, as it was also possible the most recent charge valve had an internal issue. The jury is still out. The symptom is that the charging valve cycles way too frequently, as in every twelve seconds.

All the best,

Peter
Wish I had a hyd schematic to see where possible leaks may occur. For a rough guess, I would cap each wheel motor brake line off one at a time and see if the leakdown goes away when you isolate the leaking brake.
I was wondering how the park brakes worked. By your description, they are held in the on position by stored oil under pressure from the accumulator? If/when it leaks down, you loose your park brake, correct? Most manufacturer's brakes fail safe, and need oil pressure to cage the brake springs to release. If you are not sure, these still could be that way and the accumulator is to hold them released when you use too many functions at one time, like raising the bucket and steering with engine at low idle.
 
   / Welp, baptized my PT-425 today. #18  
Wish I had a hyd schematic to see where possible leaks may occur. For a rough guess, I would cap each wheel motor brake line off one at a time and see if the leakdown goes away when you isolate the leaking brake.
I was wondering how the park brakes worked. By your description, they are held in the on position by stored oil under pressure from the accumulator? If/when it leaks down, you loose your park brake, correct? Most manufacturer's brakes fail safe, and need oil pressure to cage the brake springs to release. If you are not sure, these still could be that way and the accumulator is to hold them released when you use too many functions at one time, like raising the bucket and steering with engine at low idle.
Sorry to have not been clear with my description.

You got it. The brakes work like air brakes in trucks or trains; pressure holds them off, spring pressure turns them on in the absence of counter pressure. My limited understanding of the charging valve is that it takes the hydraulic line for steering and the FEL as input, diverts oil to the accumulator/brakes until the critical pressure is reached, and then it diverts the full flow to steering/FEL. That is why it is so noticeable when it bleeds down. There is a "clunk" that you feel through the steering wheel as the hydraulic oil is momentarily diverted to recharge the accumulator. For me, it seems to happen when everything is warm, after I have been using the tractor for awhile.

I tried the lazy route of trying to accelerate against the brakes to see if there was any slippage, but nothing visible.

Terry had me drive it another 20 hours to see if it stabilized. Coming up on that soon.

All the best,

Peter
 
   / Welp, baptized my PT-425 today. #19  
We're both thinking the same thing. I checked all the connectors in that "cluster" up front just to be sure it wasn't a missed assembly step. There was only the one that was loose. I WAS working the 3rd function a lot with the hoe, so I probably did cycle it a lot more than usual that day.

Hey on that center pin, I see the grease zircs and was planning to give them a squirt at the 50 hour service. Do they need it more often than that? I've been watching the other linkage pins and those seem pretty good to go. 12 hours on it today.
One other item: there is a grease point on the forward end of the articulating "dog bone" that is behind a metal plate on the tunnel. Almost impossible to know that it exists unless you go looking for it, and where I absolutely need my locknlube connector to ensure the grease goes in the zerk, and not around it.

All the best,

Peter
 
   / Welp, baptized my PT-425 today. #20  
I would like to hear about your accumulator issue when you figure it out. Someday I am sure I will be doing the same.
 
 
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