JD 400 Backhoe pulsating weak hydraulics

[J_J]

The JD400--Industrial version of the 2020

Is your hyd system open center or closed center?

Tractor specs says it is closed center.

You need to know what your tractor hyd pressure should be.

Install a 3000 psi hyd gage in the IN port of the FEL valve, or at the IN port of the BH valve.

Max out each of the BH cyl and check pressure.

The pressure relief on the BH should be set the same as the FEL valve relief.

You could inspect, clean the relief valves.

 

[olde man]

unless you're familiar i wouldn't take it apart. i would flush it blow it out with air use a light to inspect all the holes you can see. there should be a tiny port dead in the center that balances the pressure so that the valve works smoothly, also one near the threaded end, some times pending on the valve you can run a small gauge wire through them and clean them, either one can cause your problem. with some valves it is better to just replace them. not all are easily rebuildable.if you still want to try take note of all the parts you remove and put them back the same way. remember this is the part that keeps things from blowing up. i suggest that unless you find evidence of contamination and are able to clean it. replace it it's probably time anyhow.

 

[JimmyBOD]

Honestly, JJ., I don't know. Most of the posts I've read say these tractors are closed systems. In another post I found the moderator said the Pressure Relief Valve in located under the floor plate on the the right side of the tractor. Will go look at that.

 

[JimmyBOD]

I want to thank everyone who has posted info to help me with this issue. You have given me many things to work on. Also would like to post a picture of a part that I found in the fluid when I drain the hydralic fluid from the plugs around the filter. It is a small part that might have contacted a spring of something else, don't know what. I took it to the JD dealer, head mechanic in Parke, he was too young to have worked on these tractors so he wasn't any help. Anyone know what this is and where it goes?

 

[jinman]

When your hydraulics start to surge, have you checked the reservoir to see if there is foaming. Air leaks into the system during high fluid demand could be sucked into the pump and give you surging much like fluid starvation. Just to be on the safe side, I'd inspect for tight fittings along the suction lines and check for foaming caused by air.

 

[J_J]

If your hyd system, is closed center, all valves are in parallel, and there maybe only one relief located close to the pump.

There are replacement valves that can be converted to closed center and will have a relief valve on them.

Hydraulic machinery - Wikipedia, the free encyclopedia

Skip down to the closed center area.

 

[Gale Hawkins]

See if you can work the tractor for half a day. we just blew an o ring at transmission case connection. Ours was slow and iwork at first. after it work for wall the fluid was low. after we got it full it was okay. running seafoam in it at this time.

 

[JimmyBOD]

That is the funny thing about the way the tractor acted. First the main pump leaked around the spline shaft. The JD dealer wanted to put a reman pump at the get-go. Then he decided he would try to just install the seal. It worked. No leaks. I used the tractor for about 4 days and it seldom pulsated.

When the tractor started pulsating alot I had the JD dealer work on it. They cleaned out the screen filter and replaced the filters and the tractor did not pulsate.

When I tried to dig with the hoe at a job site, it pulsated a great deal and had no power. I doubt the JD dealer checked to see if it had power. I know he never put gauges on it to see what the main pump was all about. The dealer is thinking the pressure control valve is the problem. But they work on green tractors that are new and don't know much about old yellow iron. The pictures they gave me about the pressure control valve don't resemble what I find on this tractor.

 

[olde man]

that part looks like some sort of poppet possibly from a valve should be a spring somewhere in there also

 

[JimmyBOD]

The tank above the main pump is full of fluid. When I open the nut on top of the tank, there are three hoses that connect into the bottom of this cap, fluid flows out. So the tank must be under pressure and full of fluid. One of the hoses go back to the bottom of the main spline pump. One goes to a housing that sits behind the fan above the crank pulley. I think this housing has something to do with the power steering and the reverser. One line, rubber hose, goes to the top of the shift box. I'll check these for leaks. Thanks