Blown shaft seal On PTO hydraulic pump

[Johnny P]

Hello there,

I have read with interest numerous problems and problem solving about the JW03 backhoes. I have one of these. Whilst using the backhoe after very little use the whole hydraulics died. Not even the stabalisers would respond. Listed here are actions I have taken to rectify the problem(s). Before tackling this I had no experience of hydraulics so it proved a steep learning curve.

Changed the oil (ISO 32)

Changed the suction filter. The original one had disintergrated. I hoped this may have caused a blockage somewhere and after a good clean would sort the problem.

Dismantled the valve control block, cleaned and rebuilt.

Inspected the pressure relief valve and all appears ok.

Still nothing, only frustration.

I then read a post where someone had replaced the spring in the check valve as this had become weak. This I did and low and behold I got movement in the stabalisers and in the boom and dipper. As the backhoe was only connected to the tractor, Jinma 284, by the hydraulic pump, the backhoe frame I had detached from the tractor, I did not want to push my luck too far incase of uncontrolled movement and case damage to anything. I then eagerly attached the backhoe and frame to the tractor so I could use it to dig a vegatable plot for my patient wife.

My exitement was short lived as I realised that the shaft seal on the PTO hydraulic pump had blown. After much cursing and struggling to take the pump off, (with the backhoe now mounted on the tractor) I replaced the seal and tried again. The same thing happened the shaft seal blew, filling the gearbox with my new oil. It is expensive here in France.

Sorry to be long winded, but I thought I must relay everything I have done to avaoid numerous threads to find this out.

Does anyone have any idea why the shaft seal have blown. Thanks

 

[DwayneB]

Does anyone have any idea why the shaft seal have blown. Thanks

Yes, your blockage in your backhoe or saftey valve set too high caused the pump to blow the internal o-rings. You will need a complete rebuild kit to get it working again , that is if the casing is not cracked. Then it will be a new pump.

Sorry

 

[dfkrug]

Unfortunately, PTO hyd pump setups do not normally have their own
relief valves unless you add one. This means you are totally dependent
upon the RV in the hoe stack valve to protect the system. If your
filter disintegrated as you report, debris will have been pumped thru
your whole system. Not good. As DWAYNE says, your RV on the valve
is now probably set too high, or it has crap in it.

Always check pressure with a guage if you have to set the relief. Start
extra-low, and work your way up to the target working pressure. You can
also buy a stand-alone RV for not too much $ (or Euros).

 

[Johnny P]

drkrug,
Thanks for the reply, As I hadn't got a pressure gauge, one ia at the top of the shopping list, I set the adjuster nut as low as possible. I am not 100% sure that the PRV is completely put back together properly. One part did not want to come out when I dismantled it, On a publication I saw there was one extra piece to the PRV, possibly the part in question. All the other bits were the same as mine. I did not want to force it in case of damage. It did however, have an o ring on it so I assume it should come out.
I also replaced the spring on the top of the PRV which I believe is a "check valve" and this allows the oil to be dumped back into the tank. I imagine this happens when the controls/valves are not being used. I was wondering if the spring was too strong and would not allow the "check valve" to function thus causing a build up of pressure that way. Just a thought.

Thanks Johnny P

 

[Johnny P]

Yes, your blockage in your backhoe or saftey valve set too high caused the pump to blow the internal o-rings. You will need a complete rebuild kit to get it working again , that is if the casing is not cracked. Then it will be a new pump.

Sorry

Thanks for the reply

 

[dfkrug]

As I hadn't got a pressure gauge, one ia at the top of the shopping list, I set the adjuster nut as low as possible. I am not 100% sure that the PRV is completely put back together properly. One part did not want to come out when I dismantled it, On a publication I saw there was one extra piece to the PRV, possibly the part in question. All the other bits were the same as mine. I did not want to force it in case of damage. It did however, have an o ring on it so I assume it should come out.
I also replaced the spring on the top of the PRV which I believe is a "check valve" and this allows the oil to be dumped back into the tank. I imagine this happens when the controls/valves are not being used. I was wondering if the spring was too strong and would not allow the "check valve" to function thus causing a build up of pressure that way. Just a thought.

Johnny, I am not familiar with your Chinese valve and I do not know why
there would be any kind of check valve in or around your relief valve.
Something is keeping your relief valve from opening when it should (around
2000 psi). I assume your pump worked OK, pumping oil thru your open
center valve stack before you operated one of the levers, correct? If so,
at least your main neutral oil path to the tank is not blocked.

 

[Johnny P]

dfkrug,

Yes there was flow back into the tank. The only noticably change apart from new oil and filter I have made is replacing the spring on top of the valve, Before that no movement at all. After that movement then the blown seal. I will investigate the PRV again.

Thanks Johnny