Jinma 354 Hydraulics Pressure relief Questions

[Tim Berframe]

About 2 years ago I put in a new E320 pump in my 2006 354. Worked great - big difference.

Last fall, I put my backhoe on for the first time in a couple of years. Tried pushing a 2'X2'X1' concrete block away from the tractor with the dipper motion. Instant shower of oil all over everything as the pump split.

Just fixing it now. I will put a pressure relief bypass in with the 2nd new pump. I have some questions for anybody who knows hydraulics:



The first image shows how it is plumbed. The original PTO backhoe pump never worked from day 1. I plumb it into return line on the loader.

Image 2 shows the proposed alteration. I will put a Prince VA RV-4-H or a Princess Auto 8688947 Relief valve on pressure line # 1. Ill put gauges in by using a 'T' fitting at two locations so I can keep an eye on how hard I am pushing things in the future.

Questions:

What pressure should I set to?

Can I 'T' into the sump return line #3? If I do, do I need a one-way valve upstream of the 'T' on line #3? (This is a hard line)

Should I drill and tap a new hole into the sump to run the bypass hose into? Should the oil return below the liquid level in the sump?

Do you see any flaws in my plan? Will this fix, as proposed, avoid the same issue when I go out next weekend to finish moving those heavy concrete blocks?

(I am learning hydraulics slowly by fixing this machine. It seems to my logic that this machine is plumbed wrong to begin with. Shouldn't the pressure line off the pump go to the proportioning valve first so as to always give the steering first chance at oil flow. Also the pressure relief is in there? It has a Koyker loader so I guess it came from factory hard line plumbed without consideration of a loader circuit. They plumbed it this way so they did't have to replace hard lines?)

Thanks for any help,

Tim

 

[quicksandfarmer]

I think it's a good idea, see my post on this thread for why. Although in your specific case the valve on the backhoe should have a PRV and it should have released, you probably want to check that anyway.

If you have the gauge, see what the PRV's on the FEL and 3PH open at and set your inline one at the higher of the two.

If your 354 is like mine you're going to need to drill a hole in the sump and tap it for pipe thread. I would do it above the fluid level to minimize the chance of it leaking. Let us know how it goes.

 

[Bob Rooks]

Your Prince/Princess valve can tee into line #3. I have four reliefs/leak-offs/returns tied into a single common return line. It's not a problem unless they all let go at once, which is impossible. Your pressure gauges are going to read the same, so I assume one will be permanently mounted on the hoe.
Yes, the backhoe valve stack has a relief valve the that exhausts through the return line. No doubt it is jammed with debris. Just about all of these systems operate at no greater than 2500 psig. I wouldn't exceed 2200 psig.

 

[quicksandfarmer]

The question of whether to tee into line #3 is what derailed my still-unfinished project to add remotes to my 354 so I'm interested in what you decide.

Here is what gave me pause: as you note, line #3 is a hard line. To tee in, I think you would have to cut into it. At both ends are banjo fittings with essentially no clearance, so there is no possibility of teeing in at the ends. I don't know what kind of fitting to use to tee into a cut hard line, I suspect it would be a compression fitting, and I worry that the pipe is a weird metric diameter and I wouldn't be able to find a tee. (The good news it's a low pressure line). At the time, I could not find a dealer who stocked the line, so I decided not to cut it until I could find someplace to buy a replacement if I messed it up.

The other concern is that pipe #3 has a very small diameter, it looks to be about 3/8" or 8 to 9mm. My understanding is the return line should be larger than the input line, which would not be the case.

I have examined the tank closely and there is no drain port or unused tapping. I think the best way to proceed is to take the seat off, take the lid off of the tank, and drill a hole in the lid and tap it for 3/4" NPT. I'd put an elbow with a hose in the tapped hole, and then a quick-attach on the other end of the hose so you could tee in as many returns as you want. The lid would have to come off to keep metal shavings out of the sump. The hole would have to be positioned carefully to avoid interfering with the motion of the seat.

But I haven't done this yet. So I'm curious to see if it would work.

 

[erj]

Tim,
I haven’t gotten to your questions yet. I am still trying to understand your initial problem from the description and drawings.

Both your drawings show 1 pump and I am confused about the statements:

“Instant shower of oil all over everything as the pump split.” (was this the hydraulic pump bolted to the engine and shown in the pictures?)

“I will put a pressure relief bypass in with the 2nd new pump” (is this a second pump to be installed on the tractor that is not shown in the pictures?)

“The original PTO backhoe pump never worked from day 1” (is there a separate PTO pump for the backhoe that is not shown in the pictures?)

“I plumb it into return line on the loader.” (that would not give the pressure required for a backhoe pump, unless it was connected to a Power Beyond port on the Loader valve.)

If you have a PTO backhoe pump, how is it supposed to connect to the PTO?

If you have a PTO backhoe pump, does you backhoe have a self-contained hydraulic tank?

 

[Tim Berframe]

There is only one pump in the system - hanging off the back of the engine timing case.

There will be a new replacement pump (the second time I have replaced it).

There used to be a PTO pump for the backhoe with its own sump tank. That PTO pump was broken from factory and never worked right ( there are likely old posts on here from me when I was trying to figure that out). It is removed and the tank is unused. I split line #2 with quick connects and connect the back hoe there.

My incorrect language - Line #2 is the only line out of the loader valve. It goes to the priority valve at high pressure.

 

[Tim Berframe]

quicksandfarmer,

I had a lot of problems with the small diameter hard lines on the backhoe cylinders when new. I cut the fittings off all of them and the local hydraulic shop welded imperial fittings on them so I could use standard hoses.

I am thinking I will have to cut a section of line #3 out. Weld fittings to the ends. Insert a short length of rubber hose/fittings to accommodate the 'T'.

The return fitting on the relief valve available to me (Princess Auto is Canada's version of Harbour Freight) Princess Auto 8688947 is smaller than the through ports. If the valve itself only has a certain size outlet, then there is no advantage to a larger hose? In that case, the 3/8 line should be fine?

I guess it comes down to which is easier/quicker/cheaper - 'T' into existing return or drill and tap the sump cover.

 

[quicksandfarmer]

I think (and I'm no expert) that there's no point in the return hose being any bigger than the outlet on the valve. So you should be fine. Welding in a T sounds like a reasonable thing as well.

 

[Tim Berframe]

It has taken a while but I did finally do this fix so I thought I would update the post for any future readers.

I installed the 2nd replacement e320 pump. It leaked with engine at idle. I took it apart and it appeared that the seal was not in the groove when assembled so it was pinched. The Texas dealer helped me out with a repair kit. I put it in and promptly blew the seals in a gush of oil after only 10 minutes. Took it apart and found several things of note. The pump bolts together with two cap screws. The heads are longer than the recess they fit in and therefore the pump doesn't mount flush to its mating surface (ground them flush) The grooves milled into the pump halves are round bottomed on this one. The seals provided are square cut. The grooves are deeper than the seals are thick. I took apart the Chinese pump that mounts on the rear of the tractor that originally came with the backhoe. The shaft seal on that was bad from factory. Luckily, the seals are the same shape and much thicker. And the outer seal is round like an Oring so it matched up with the round bottom grooves better. Put the e320 back together and tried again. Anything over 1400psi would cause it to leak. That is not enough pressure to lift the 3pt with backhoe on it nor was it enough to operate the lift arm on the hoe. Took it apart again. Bought a digital caliper. Discovered that the depth of the seal groove is very deep at the point it leaks (which also happens to be the point where the first seal was pinched and it blew apart the 2nd seal). I ended up mixing parts from the two e320 replacement pumps to get the shallowest grooves with the thickest seals. 5th attempt seems to have worked.

I bolted the Princess Auto valve onto the loader support. I removed all quick connects from the system. Added a gauge between the pump and the loader (first device in the pressure circuit). I used a weld-on 3/4" female adapter to attach the relief line to the sump. I ground the bottom a bit so it goes over the fill plug hole without disturbing the threads in case I should want to go back someday. I tried JB weld but it didn't hold. Ground the paint off the sump cover and zapped three little flux core mig welds to hold it. Cost about $300 of hoses and fittings to rig it all. I used 3/4" air-seeder hose to run the breather up the ROPS. I was planning to make a rain proof cap but I think the loop is all it needs.

I backed the relief valve all the way out (supposed to be 400 psi lowest setting) and gradually increased it to try to see where the loader and 3pt are set. I figured as long as the new relief is tripping, the others haven't reached their limits. I worked the bucket to its curl travel limit and held the stick over to see where the gauge leveled at. I am all the way up to 2400psi and the new valve is still releasing. After blowing pump seals 3 times, I am nervous to go higher but for the fact that I still don't think the loader relief has tripped yet.

This is a concern because I now have no power steering. I can strong arm it with about 4.5 full turns of the steering wheel. It turns a little easier to the left for some reason. Is it possible that it requires more than 2400psi to operate the steering? OR have I broken something else coincidentally? The gauge doesn't change when I try to turn the wheel so perhaps there is no flow to the steering.

1 step forward, two steps back.....

 

[RonMar]

Isn't the 354 power steering powered by a separate PS pump?