charging pressure too high on Bobcat T300

[bigboytoy]

so i took out the charge relief ...a spring loaded relief in an hard to get to place .... I take it out inspect it looks normal and put it back in ...in one try ... I add a shim washer to the stack to tighten up the relief ... and oh **** i can't get it in... doing the math a thin 8mm washer should raise it 30-50 # ... its very difficult to get it back in and Im working on methods.

 

[TVA]

Well! It’s counterintuitive! Your charge pressure supposed to go down when you put a load on the drive!
Is your machine pilot or mechanically controlled? Specs for your charge pressure tells me that there’s something else in that circuit! Probably pilot circuit.
Usually charge is 250-350, but if there’s something else upstream or parallel then OEM rase the specs on circuit pressure.

What you described looks like that something else is draining your charge pressure at neutral little bit too much.

My suggestion is stop with that “ snake oil shimming” thing and get to real cause of the problem!

 

[TVA]

Another thing: your original code watch charge pressure too high, now your too low but it goes up under load. I know only one component that can cause both symptoms - charge shuttle valves! Especially if you have some moisture in the hydraulic fluid and machine sat for a while!

 

[bigboytoy]

"uncle" I give ... can't condense spring with that little sliver of extra shim ... new spring and bobbet on order

 

[bigboytoy]

well it jumps around like the whole cab and me when i'm reading the gauge .... I rev it up is when it goes up ... the pressure jerks around , can say its a definite rise with out a redo test... so I will post this week after I get parts.

 

[TVA]

Good luck!

 

[TVA]

These might help:

 

[bigboytoy]

its a mechanical controlled machine. Its has an error code but there are no symptoms as far as anything not working right. Code is triggered at low idle. Gauges tell me it is low according to manual. The relief parts could be worn but I can't see it, well maybe when I get the new ones I can tell. My guess is the shims are maxed out at 4 installed, making it any thicker is impossible to install, I got to have enough room to start first thread. You guys are a big help in helping me understand things. A new spring could be stiffer and that's all that is needed. we will see.

 

[bigboytoy]

put new spring and bobbet in removed 2 slim shims to equal what I took out.... I knew I could get the same that came out back in ...I did not try more than that, that was hard enough... pressures increased slightly from 375 to 390 at low idle ... warm and under load it was 420 about the same ... I did notice i could turn with out stall ... hmmm ... I was just use to it stalling if I turned too fast ... seems much better ... still got error message of low charge pressure. Its fine for now I got dirt to move. I will leave gauge installed for a while. My test run was short... i run it a lot harder for hours.
I could get more shims in to raise pressure if the engine was out. probably just ignore the code til I get more symptoms. any thoughts?

 

[Spooky]

First thing you need to check is the charge pressure switch at the hydraulic filter, it would be the switch with three wires going to it. See if the switch is leaking fluid into the harness connector plug. If it is that will foul up the electrical information being sent to the main controller. If it's not leaking I'd consider replacing the switch anyway, it could be faulty. There's no way for you to test that switch as it's a Hall Effect sensor.

I have a 2004 bobcat t300 i just replaced my right side final drive motor now the other side is squeaky but only when the hydraulics lose power ever so often my machine will shut off and says hyd charge pressure shutdown this is my first skid steer and im pretty lost

 

[TVA]

I have a 2004 bobcat t300 i just replaced my right side final drive motor now the other side is squeaky but only when the hydraulics lose power ever so often my machine will shut off and says hyd charge pressure shutdown this is my first skid steer and im pretty lost

What was the reason for replacing final drive? Was it hydraulic side problems or planetary side?

Is the right side has power now. Asking because if it was hydraulic side problem, the debris from the motor damages the pump also.

 

[Spooky]

What was the reason for replacing final drive? Was it hydraulic side problems or planetary side?

Is the right side has power now. Asking because if it was hydraulic side problem, the debris from the motor damages the pump also.

We replaced the right side cause it was squeaking real bad and we looked inside and there was alot of metal shards inside it was the brakes part of it that was bad

 

[TVA]

We replaced the right side cause it was squeaking real bad and we looked inside and there was alot of metal shards inside it was the brakes part of it that was bad

So the loop didn’t get the metal shards?
Metal shards will plug your filters very fast. They will make bypass on the return filter open up and render that filter useless.
Also of your parking brake and high speed circuits powering off of the charge circuit - leak in the parking brake will drop the charge pressure.

 

[Spooky]

Where would the charge circuit be at we cleaned all the filters out we was going to wait till we got the machine working right before we bought new one but we drain and replace the hydraulic oil multiple times

So the loop didn’t get the metal shards?
Metal shards will plug your filters very fast. They will make bypass on the return filter open up and render that filter useless.
Also of your parking brake and high speed circuits powering off of the charge circuit - leak in the parking brake will drop the charge pressure.

 

[TVA]

Where would the charge circuit be at we cleaned all the filters out we was going to wait till we got the machine working right before we bought new one but we drain and replace the hydraulic oil multiple times

If you hear the squeaks - it means you’re other brake piston seal is leaking, and you burning another set of brake discs.

 

[Spooky]

If you hear the squeaks - it means you’re other brake piston seal is leaking, and you burning another set of brake discs.

Yes thats what i was thinking if i get replaced do you think thats what is causing the hyd charge pressure shutdown

 

[TVA]

If you hear the squeaks - it means you’re other brake piston seal is leaking, and you burning another set of brake discs.

And you can’t clean the return filter. You can clean charge filter - but replace them after failure like this, because tiny particles are still stuck in that mesh.

 

[Spooky]

And you can’t clean the return filter. You can clean charge filter - but replace them after failure like this, because tiny particles are still stuck in that mesh.

Ok I appreciate it i will keep you posted and see what happens

 

[TVA]

Yes thats what i was thinking if i get replaced do you think thats what is causing the hyd charge pressure shutdown

The plugged charge filter - of course.
Also leak in the brake piston. I was about to work on 300 once, but it didn’t happened, so I don’t remember where the parking brake and high speed gets powered from. But majority powers from the charge circuit, or at least from the same gear pump.