JD 410B No Hydraulics

Got a JD 410B backhoe. The hydraulics were a bit slow on it. I changed out the filters and topped off the fluid. Still Slow.
So I decided to Rebuild the pump. Before removing the pump everthing worked; just worked slow. Had plenty of power just wasnt very fast. So I removed the pump and rebuilt it. all new seals and shaft bearings. Once put back on the tractor I now have NO HYDRAULICS. I started it up and backed off all the lines to the pump. I have charge oil coming in from the filter. I have return oil coming in from the trans. I have high pressure going out. I have very little to no charge oil going out.

So I have oil coming into the chargepump but none going out of it. When I took the line off the charge pump that brings oil into the charge pump I have oil. When I take the line off the charge pump that should be taking oil back to the filter I have very little of anything. There is alittle bit of oil but its mostly air that is pumping through. You can hear it pumping or i guess the gears turning is what your hearing, but no oil coiming out. It seems like the gears inside are spining correctly I even took the charge pump back off to make sure there was no binding or broken parts and seen nothing. It seemd just fine to me.

Any help would be great.

Thanks
Mark

As far as I know, the charge pump has to suck the oil from the transmission, and a gear pump is not a very good air vacuum pump, so I'd try to prime it before starting it up. Use whatever you have for a vacuum pump to suck the air from the line between the charge pump and filter, then put it back together and start it up.

I'm curious what you found when you rebuilt it, how did the pistons and valves look? I hope the main hydraulic pump was oiled before you started it up.

Delmer.

When rebuilding it the valves and pistons all looked good. However I did replace them all since they came with the kit i bought. The shaft bearings seemed a little loose so I had them changed out. When pulling the bearings off I found that the lobe needle bearings had been eatten up a bit, but those were all replaced as well. Also the shaft did have some minimal wear on it, but the guys at the shop said it should be ok.

So the line that is coming from the trans has oil coming up to it. I started the hoe up and backed that line off a few turns and the fluid starts pouting out of the line; so its def getting fluid to the pump. However its not coming out the other side of the pump. which doenst make any sense to me.

I suppose take that charge pump apart again, either it's blocked or it's not turning, right? any chance there was a key or coupler in the middle that got left out? can you have somebody turn the engine by hand and see the gears move from either end?

Suction screen clean?

It doesnt sound like your charge pump is right. Did you replace the end plate seals also in the charge pump?

Thanks guys. I got it back to working. However everything is still the same as it was before I rebuilt the pump. Unless your about 1/2 throttle or better the attachments dont really move. While using the bucket to dig I can only make one movement at a time. For example I can bring the dipper stick in but I cant curl the bucket at the same time. Its like theres not enough hydraulic power to move the machine the way its supposed to.

mg2361 asked if you cleaned the screens.
Did you clean the priority valve screen ?

you're going to need the operations and test manual to get much further. You could start with the pressure tests, we already know the pressure is dropping with any flow at all, the charge pressure might not be keeping up, but there's lots of possibilities for that too, the manual goes through everything.

One way to cheat, you can start it up cold and let it sit at low idle for a couple minutes, then go to the different valves and see if any of them are warmer than the others, like priority valve, loader, backhoe, steering, brakes, follow all of the lines off the hydraulic pump to the priority valve and every where else they lead. If one of them is much warmer than the others, that's where it's leaking, if all those valves are still cold, then more likely you have a pump problem.

Any chance the front loader acts better or worse than the backhoe?

Is this one of those old radial piston pumps that has a constant standby pressure? (somewhere around 3000 psi if I remember right)

i think originally they were 2250 -2500 but i could be wrong. too much pressure and those radial pumps will blow out one of the outlet valve plugs. maybe the de-stroke valve in the pump is stuck or set too low

Is there any chance the destroke valve is your problem ? Did do anything with the manual screw ?
There is a slim chance the oil cooler needs a through flushing.

Ok. So I was out trying to get to the suction screen to check it and found what I hope to be the problem. The suction screen is located in the side of the trans.
There is a L shape connection to it for the hose to connect to that comes from the pump. Once I removed the pump hose from said connection you could see that the connection had been smashed and almost completely closed off. Also the connection was not tight. It was loose which allowed the connection to swivel into an upward position instead of being level; which would reduce flow even more. I have fixed the connection but am currently waiting on the new suction screen to come in. The screen itself wasn’t clogged. It actually looked pretty good in terms of cleanliness. But it did have 2 hole in it about the size of a pencil eraser. So I have one on order and am currently waiting on it to put everything back together. I’ll give updates once it all back together.

Vetech63 said:

Is this one of those old radial piston pumps that has a constant standby pressure? (somewhere around 3000 psi if I remember right)

Click to expand...

Yes, and he never complained about pressure/power so that might mean the pressure is set correct. The smashed fitting is as good an answer as any for the low volume/speed. Let us know how it turns out.

So after getting it all back together I still have the same problem. I have just pulled the priority valve off today to thoroughly clean it check it over. I ordered a pressure test kit so I can check the standby pressure and a few other pressures, but thats not going to be here until Sunday; says amazon.