B7200 three point problems

[Fellenz]

Hello Everyone,

I have a B7200 with a front loader. Over the last year I've had some issues with the three point where it will either not work at all, work slowly, or act jerky.

Right now the three point seems to work pretty reliably when the tractor is first started but after a few minutes of running will usually become completely unresponsive under load. Sometimes when I try to lift the three point it will struggle like it's overloaded.

I've had the three point valve opened up three times this past year and have completely disassembled and blown out the valve looking for a blockage. After it put it back together it generally works okay for a little while before going back to its old tricks.

While this is happening with the three point I have no issues with the loader, and shutting the valve to the loader makes no difference. I've also changed the hydraulic fluid and filter recently.

Any ideas?

-Thanks,

Erik

 

[North Idaho Wolfman]

What model is it exactly? D, E, HSTD, HSTE?
Where is the loader connected?

 

[Fellenz]

It's a B7200D (gear shift)

The loader is connected to the outlet in front of the brake pedals.

I'm using a Brand Hydraulic joystick valve from Surplus Center with a power beyond sleeve that dumps back to the sump.

 

[Fellenz]

Okay, just to ensure I'm barking up the right tree I completely disconnected the hydraulics to the loader and switched the valve so all flow is going directly from the pressure side of the pump to the three point valve.

I did not notice any change in behavior when I did this. The tractor had been running for ~15 minutes at this point and the three point was struggling to lift. When I first started the tractor the three point worked fine for the first ~5 minutes and the loader worked fine the entire time until I disconnected it.

This issue is really throwing me. I'm pretty sure if I let the tractor sit for an hour and start it back up the three point will work fine.

I'm wondering if it might be the pump going bad and losing pressure as the oil heats? I'm going to plumb in a gauge next and see what it tells me. I'll also check the newish filter and see how it looks.

Does anyone see something stupid/simple I might be overlooking?

-Thanks,

Erik

 

[North Idaho Wolfman]

I'm betting on valve or lift piston ring problems.

I would have thought that the loader valve might be giving you an issue as it could be bypassing all the fluid to the tank, but you said you removed it from the loop and it's still doing it.

There is a bypass valve under the seat, it is turned in the right direction isn't it?
That will be the place to test for pressure too.

 

[Fellenz]

I'm betting on valve or lift piston ring problems.

I would have thought that the loader valve might be giving you an issue as it could be bypassing all the fluid to the tank, but you said you removed it from the loop and it's still doing it.

There is a bypass valve under the seat, it is turned in the right direction isn't it?
That will be the place to test for pressure too.

The lift piston rings were replaced less than two years ago when I had this part of the tractor apart for the first time. Hopefully they're not the problem but if everything else checks out I'll check them.

Re: the bypass valve under the seat. Is this the load descent speed valve? If not then where is it? I thought the descent speed valve only affected the drop not lift.

-Thanks

 

[Fellenz]

Well from the latest test it's looking like the pump is the culprit.

I don't have the book handy to check system pressure but I have ~1500PSI on first start when the system is cold, ~1,000PSI for the next few minutes, and then it drops to ~650PSI at wide open throttle after it has been running for a few minutes.

Luckily I have a spare pump sitting on the shelf I can swap!