John Deere 300 b backhoe select hydraulic problem

[Suzukibruce]

When I fixed the leaking diesel fuel tank I removed and drained the hydraulic tank. Filled the tank back up and filled the transmission to the proper fluid level. Loader doesn稚 work. The stabilizers work fine, some of the backhoe functions but not all cylinders are working. The tractor runs in gear and the power steering works. Is there a filter in the pump that may be clogged?

 

[Erik M]

I am guess you have air in some of the lines and need to bleed the lines to get rid of the air bubbles.

If you had drained the hydraulics it would have been a good time to change the filter.

 

[Tx Jim]

Operating hyd functions will bleed any air out of system. Yes there's a small filter in frt hyd pump but I doubt that filter in pump is at fault. Did you install new hyd filters under tractor & check/clean sump screen? I also suggest to check hyd stand-by pressure which should be 2250-2350 psi.

 

[Suzukibruce]

Operating hyd functions will bleed any air out of system. Yes there's a small filter in frt hyd pump but I doubt that filter in pump is at fault. Did you install new hyd filters under tractor & check/clean sump screen? I also suggest to check hyd stand-by pressure which should be 2250-2350 psi.

I worked the stabilizers and boon for over 1 hour with no improvement. I also changed the filters with tractor hours 3 before this occurred. The only filter I didn稚 look at was in the pump. Any idea where it is located? I believe there has been no work done to this machine in 10 years.
Thanks

 

[Tx Jim]

As I previously stated it will shock me if filter(key 17) is the problem. Just for your info I served as a JD dealer service manager from '75-'87. Closed-center hyd's such as your tractor has requires very good diagnostics when a hyd problem arises.

 

[Suzukibruce]

As I previously stated it will shock me if filter(key 17) is the problem. Just for your info I served as a JD dealer service manager from '75-'87. Closed-center hyd's such as your tractor has requires very good diagnostics when a hyd problem arises.

Started the tractor today and the backhoe responded as normal. Loader is still out. I have no way of getting the machine to JD at this point so I'm on my own. What tool would I need to check the pump pressure please.

 

[oldnslo]

If the backhoe is working properly I would suspect that the pump is not getting a pilot signal from the loader valve to go on stroke. Not sure or how to test for this pilot signal though

 

[Tx Jim]

One can check hyd stand-by pressure by installing a 3000 psi gauge on hyd pump port(kry 24)

 

[Tx Jim]

If the backhoe is working properly I would suspect that the pump is not getting a pilot signal from the loader valve to go on stroke. Not sure or how to test for this pilot signal though

Are you thinking about a CCLS hyd system? JD 300B doesn't utilize a pilot signal to put pump in stroke merely a drop in hyd pressure which allows pump pistons to be pushed back by springs against the already rotating pump shaft allowing pump to pump oil.

 

[medic0648]

Are the heavier movements not working? If so check the filter in the pump. It is in line with the pressure control internal to the pump. Check inside the transmission toward the front for spraying and bubbles. Pull the return line on the rear and start the tractor. Make sure with all the controls in neutral there isn't any flow.

 

[oldnslo]

Are you thinking about a CCLS hyd system? JD 300B doesn't utilize a pilot signal to put pump in stroke merely a drop in hyd pressure which allows pump pistons to be pushed back by springs against the already rotating pump shaft allowing pump to pump oil.

Yes I thought this was a CCLS system

Does this model have the priority flow control for steering. If the hoe is working then something is blocking oil from getting to the loader valve.

 

[Tx Jim]

Pull the return line on the rear and start the tractor.

May I ask which return line you're referring to pulling?

 

[medic0648]

I have a 301 and the hydraulic return for everything goes through a hose to the rear into the sump. I had a valve fail internally and it bypassed to the return. Nothing worked unless something down the line caused enough back pressure.

 

[Suzukibruce]

May I ask which return line you're referring to pulling?

Update. The backhoe is working but has slowed down. I changed the pump filter. It was torn and full of dirt. If I lift the loader with another loader it will stay only a foot off the ground. I believe I have air in the lines because all worked well until I had to take the fuel tank off for repairs. I am open to suggestions as to how best get the air out.

 

[Suzukibruce]

May I ask which return line you're referring to pulling?

Update. The backhoe is working but has slowed down. I changed the pump filter. It was torn and full of dirt. If I lift the loader with another loader it will stay only a foot off the ground. I believe I have air in the lines because all worked well until I had to take the fuel tank off for repairs. I am open to suggestions as to how best get the air out.

 

[Tx Jim]

Yes I thought this was a CCLS system

Does this model have the priority flow control for steering. If the hoe is working then something is blocking oil from getting to the loader valve.

Yes there's a priority valve but to my knowledge both backhoe & loader are supplied oil after oil leaves priority valve.

 

[Tx Jim]

Suzukibruce
Previous owner must not have changed other hyd filters very regularly. Did you ever check/clean hyd oil sump screen in the bottom of trans case????

 

[Suzukibruce]

Suzukibruce
Previous owner must not have changed other hyd filters very regularly. Did you ever check/clean hyd oil sump screen in the bottom of trans case????

You are correct about filter and fluid changes. The first thing I did 30 tractor hours ago was change both filters and pulled the inline screen behind the 4 inch rubber hose. What a job getting that hose back on. The oil is new hygard. I知 going to try blowing compressed air in the sump to see if I get a positive reaction with the loader. Other than that I have no other filters that I know of to change

 

[oldnslo]

The oil is new hygard. I知 going to try blowing compressed air in the sump to see if I get a positive reaction with the loader. Other than that I have no other filters that I know of to change

Blowing compressed air into the reservoir helps prime the pump but I doubt that you have an air lock to the loader valve. This is a closed center system so if the back hoe is working the pump is moving oil and this oil should also be available to the loader. Can you operate a function on the back hoe and loader at the same time? If the hoe stops working this would point towards a problem in the loader valve circuit dumping oil to tank.

 

[Suzukibruce]

Yes I tried holding the loader in the up position while operating the backhoe.when the backhoe bumps the loader will move a little. I forgot to mention that before all this happened I lost the accumulator input hose. This is probably the problem. Again sorry for omitting this. I didn’t think of it at the time.