Hydraulics: backhoe only works with 3point chained down.

[DerikL]

So I have had the tractor for a few years now and think its about time I got to fixing the backhoe issue.
When I got the tractor it the BH was not working. It didn't take me long to figure out that it would work when I moved the 3pt. So I chained down the 3pt and the backhoe has been working fine ever sence. But I would like to know what the issue is.

As long as the 3pt is chained down, and the lever is up, BH works. No relief sound but there is some load on the engine, barely noticeable.
If the 3pt lever is down and a lever on the BH is activated when I start the tractor.

that function will work until it is released then nothing else will work. Basicaly you could use the BH as long as you never released all the levers. I can leave a stabilizer in relief and the backhoe will continue to work.
There are three lines coming from the BH. One goes to hydraulic block,
Two go to loader valve.
Never had any problem with loader.



This is the only pic I had on my phone. I will go out and get pics of hydraulic block and loader valve when the sun comes up.

BTW: It's a Mahindra 3015 w/ KMW 3710 BH

 

[kennyd]

Sounds like the lines that feed your backhoe, called the "power beyond" lines are plumbed in parallel into your hydraulic system and not in series as they should be. If you can provide a drawing or good pictures we can help you figure it out-or get whoever plumbed it wrong to fix it if that's possible.

 

[DerikL]

Hydraulic block


Lines going into BH.

None of the lines can be switched at the quick connects due to length.

Edit: Screwed up my color coding, think i got it straight now.

 

[kennyd]

Great pics, that "looks" correct Derik, are the ports on the lower block marked? And the other two ports on the valve? I see the top one is PB (power beyond), the lower one I assume is T (for Tank) since it had the tee in it.

 

[DerikL]

I labeled the loader valve
The lower line is definitely Tank (If i disconnect this line the BH can extend but not retract)
The middle line that's labeled P does go to P on the hydraulic block
The top line goes to BH (or to N when BH is removed)

 

[DerikL]

Assuming N is the 3ph is seems that without any back pressure from the N port the backhoe doesn't work. Could that mean that the tank and PB from BH are crossed. How would I check this?

 

[DerikL]

Never knew this lable was under the BH bulkhead. The lines going into this seem correct also. PB from loader valve goes into P port and PB labled line goes to N on Hydraulic block. Tank to tank

 

[DerikL]

Bump. So all is well? Should I continue to run it with 3pt chained down? Or is there a problem with BH valve? Is there no pressure built in the backhoe itself? I don't understand how the BH doesn't make pressure. Should I post in hydraulics forum?

 

[kennyd]

Sorry Derik, I was out all day yesterday doing the family thing.

Something is indeed wrong, I just can't put my finger on it yet. There is nothing "wrong" with chaining the 3PH down but it certainly is not the correct way to operate things. It seems to me somehow that the lower block is adding the backhoe in parallel rather than series, I and can't figure out what the "N" port might be-guessing the internal plumbing to the 3PH maybe. From looking at the pics, and the drawing you provided it everything looks correct.

Hoping another MH owner with a backhoe can show/tell us how theirs is plumbed.

 

[AchingBack]

I have a 3710 and it appears you are correctly plumbed. I've read through the trouble shooting section of the manual and your problem is not identified. Sorry I can't offer any suggestions.