Back again JD 410 backhoe hydro problem

Last fall I replaced the broken ring and pinion on a 1979 JD 410 backhoe. After I got her up and running I blew a line to the loader bucket, replaced the line and then lost hydro pressure. It should be worth mentioning that the system was "open" for months and it I feel that it got dirty.

I had posted in here last fall and some good people where kind enough to help.

I guess the best way is to list out what I have done so far.

1. Tested the pump pressure with the rear hydraulics plugged off at the power-steering T and the pump read about 2400psi. As well I have 130psi at the reverser control.

2. Replaced both filters (tranny and hydro).

3. Cleaned the transmission screen.

4. Cleaned the transmission relief valve.

4. And just yesterday completely disassembled and cleaned the speed gear assembly (reverser) control.

Still nothing. Pump still reads only 500psi.

One thing I did notice yesterday is the hydraulic pump to pressure control valve seems hot while running. Other lines seem about the same as outside temp. I know someone had mentioned that a hot line points to the leak / problem, but where? Does that mean the pressure control valve is leaking?

Some of the things I am thinking of looking at today.

1. Bypassing the steering. Someone here suggested it.

2. Try to understand the loader control valve and clean or bypass it. My thinking is that if the loader line blew would not a influx of oil pass through the loader control valve, possibly picking up dirt and thus creating a leak?

3. Revisit the pressure control valve, due to the pressure control valve to pump line being hot.

Other then that I am at a loss here. Any help or other ideas would be greatly appreciated.

Thanks in advance.
Chris

jb

Sorry for the confusion. By pressure control valve I mean the pressure control valve at the back off the transmission, the one that diverts fluid from the hydro pump, which I might add I have cleaned out.

If I assume correctly plugging the lines at the power steering T and seeing 2400psi on the gauge at the pump means that the pump is getting oil and the pump is fine. With the line not plugged (tractor as normal), I am getting only 500psi.

So is it safe to assume that the pump is getting fluid and the pump is fine? Pump only has about 250 hours on it as I replaced that about 4 years ago.

Thanks again for the help. I just got back from the 5 gal bucket test. I think bad news as it was only about 3 gals in a minute if that. I used the clutch control valve to pump inlet line.

So where should I attempt to look next. Or is it a definite that the trans pump is shot?

Funny thing is that I have no diagrams or manual on the internals of the trany. I am using the CD-ROM manual which is nothing more then a Military manual. Seems to cover everything but the internal of the tranny.

I assume getting to the tranny pump is tedious and costly? I have spent more time trying to find the problem here and would hate to go all the way with the tranny pump replacement only to find it not the problem. Going off the deep end here. :)

One last thing. The brakes are empty and I have not bleed them yet, but now I see in the manual that the brakes are fed from the tranny? I will have to look again, but I thought they were a completely independant manual system with no feed from the tranny.

Thanks again for any more help that anyone has to offer.

Thought this would help..... maybe not?

Thanks again.