B7100 pump seal blowing

[Rocketman.tractorbynet]

need some good hydraulic help here. I have only had this tractor a short time. Previous owner had pump seal replaced 19 hrs earlier. seal is blown again. fills crankcase and comes out vent tube. I disassembled and found no other problems in pump. When using loader, it has plenty of power, but bucket is very slow, and I can not shake it. the boom moves quicker and has faster responce. when either cylinder reaches stop it puts a load on the engine. I think the pump is OK,.... but where is the problem? any ideas?

 

[J_J]

need some good hydraulic help here. I have only had this tractor a short time. Previous owner had pump seal replaced 19 hrs earlier. seal is blown again. fills crankcase and comes out vent tube. I disassembled and found no other problems in pump. When using loader, it has plenty of power, but bucket is very slow, and I can not shake it. the boom moves quicker and has faster responce. when either cylinder reaches stop it puts a load on the engine. I think the pump is OK,.... but where is the problem? any ideas?

I believe it might be your relief valve. What usually blows a pump seal, is over-pressure, and this can be caused by blocked hyd fluid. When you push or pull the hyd cylinder to the ends of travel. the hyd fluid has no place to go. If it were not for the relief valve, something would blow or burst. The weakest component in the system is the first to go, be it a hose, valve seal, cylinder seal, pump seal, or the pump case will crack. When you hear the engine labor, something is blocking the hyd fluid. You might try and clean the relief valve. If it is working properly, you can usually hear it whine. What the relief valve is doing, is bleeding off excess pressure. If it sticks open , you will have low pressure or relief pressure. If it sticks closed, something will blow or burst.

Every time I try and answer hyd questions, I will suggest a hydraulic gage. With the gage and some hydraulic know how, you should be able to trouble shoot your hyd system.

Check the hyd fluid level. Check your filter. About the only reason for the hyd fluid to come out the vent tube is over heated fluid, and over filling. If the pump is sucking air, it will cause the fluid to expand. Is your fluid getting hot, and does it have air bubbles in it? Compare your fluid to some new fluid. If you don't like what you see, change out the fluid, and only fill to correct level, when warm.

 

[Thomas]

J.J.
You do give some great advice!!!..by chance are you our have been service tech?

Always looking forward to your reads and others.

 

[J_J]

J.J.
You do give some great advice!!!..by chance are you our have been service tech?

Always looking forward to your reads and others.

Thanks. When I was young, I needed some good advice, and didn't get it. I did learn to use what knowledge I had to acquire more knowledge. As a Navy electronics technician, and later antisubmarine warfare operator, I learned to analyze things, and used the same technique that is used for electronics trouble shooting, You can work from the good end to the bad end, or back the other way. Same technique for hydraulic trouble shooting. The hydraulic gage is a necessary for good hydraulic trouble shooting.

No, I didn't go to school for hydraulics, but I operate lots of hydraulic stuff, and to poor/cheap to pay someone else to do something that I think I can do. So I essentially learned by doing, and researching the data that I needed. There is a lot of hydraulic stuff that I don't know, I try to keep up with things I need to know.

 

[Rocketman.tractorbynet]

quick follow up... is there only one relief valve for the 3ph and loader, or is there a separate one in the hand controls? I am also thinking there may be additional problems in the control, ie, slow movement on the bucket and quicker movement on the boom.

 

[kenstrac]

there should be a relief valve on the loader control and 1 on the tractor I would check if you have quick disconnects on the loader to see if they are in there tight and seated then I would swap the bucket and lift circuits and see if the problem follows.
the pump might have been rebuilt BUT was it done right? I have seen people replace the seals and there is a groove in the shaft and it only last a short time before the problem arises again if there is a groove on the shaft than it can be fixed with a speedy sleeve

 

[J_J]

quick follow up... is there only one relief valve for the 3ph and loader, or is there a separate one in the hand controls? I am also thinking there may be additional problems in the control, ie, slow movement on the bucket and quicker movement on the boom.

I am not that positive about the relief for the 3ph, but in general, the 3ph will have it's own relief valve for this reason. Some tractors do not have a loader, and the fluid going to anything hydraulic has to have a relief valve someplace. I believe that all loaders will have a relief valve in, on, or between the pump and the loader valve. Some of the Kubota guys probable can tell you more about specific units. A hydraulic schematic diagram would surely help with your particular model.

 

[Rocketman.tractorbynet]

more questions... How does the hydraulic block work? It is inline on the pressure side from the pump, right? Then 2 hoses branch off to the loader control, right? One inlet, one outlet on the valve. How can the outlet come back to that hydraulic block? Is this outlet hose not less pressure? Is it possible that the seal(mentioned above) blew out when and if the loader was dropped with a load when the engine was not running, assuming the fluid backed up to the pump through the hydraulic block? I can not see any other way that any pressure could get to that seal.

 

[kenstrac]

Do you have a pic of the block? is the block a diverter valve? if the block is mounted to the tractor body it could be internally ported. Does your 3pt work OK?

 

[MikesTractor]

It has been a while since I have had a B-7100 in my shop, but if I remember right, the diverter block has 2 ports (some of the earlier tractors didn't have a power beyond port) on the side. By hooking the loader inlet and outlet to these 2 ports, you are simply putting your loader valve in the flow of oil.

With the loader valve in neutral, all of the oil continues on to the 3ph. When you move one of the loader valves, all oil is directed to that function, robbing oil from the 3ph until you are through with that function. All oil, whether it is exhaust from loader or pressurized pump flow will continue to the 3ph.

Hope this helps.

Mike