backhoe hydraulics

[80cj]

I bought a Woods BH70-X (with thumb) for my Massey Furguson MF1532 with FEL. (Both purchased new 12/31/08, backhoe was installed ~Feb 09 @ 30 hours on the tractor) A fitting on the backhoe was broken during shipment to the dealer and had to be replaced by the dealer, so the smell of hot hydraulic fluid while operating it was expected. I was very pleased with the backhoe and it's strength. It easily picked up logs and rocks and moved them around.

By 50 hours (20 with backhoe attached) the backhoe lost power to the point that, with the boom fully extended, it would no longer pick up the bucket when it was full of mud. i have not used the FEL enough to say if i can tell a difference in its strength for sure, but of course it 'seems' weak too. also, not sure if it is related, but i'll throw it out there, the tractor has developed a leak from mid-body/clutch area.

i had the recommended 50 hour service performed at the dealer, but it has not fixed the problem. (he thought it was the filter) it is still much weaker than it previously was. i suspect that it may have air in the hydraulic lines, the boom is springy and jerky. i looked in the manual, but was not able to find a bleeding procedure and i dont believe that bleeding at the tractor bleed point will work since the backhoe is higher (and has dead headed lines). any help would be greatly appreciated.

i sent the above info to Woods customer support and they gave this reply:
"If there is air in the system by cycling the cylinders several times through the extend and retract cycle will purge them of any air."

any ideas?

thanks
shawn

 

[KennyV]

The air will be removed with normal cycling of the cylinders... no need to do anything special. have your dealer measure the actual hydraulic pressure. KennyV.

 

[80cj]

i read on another thread that the fittings are designed to let the air leak out, but not the hydraulic fluid. that seems a little hard to believe, but other than that, i can't think of any way that it could work.

can someone tell me if it is normal for the boom/bucket to bounce up and down and if i should be able to smell hot hydraulic fluid?

thanks
shawn

 

[kennyd]

i read on another thread that the fittings are designed to let the air leak out, but not the hydraulic fluid. that seems a little hard to believe, but other than that, i can't think of any way that it could work.

can someone tell me if it is normal for the boom/bucket to bounce up and down and if i should be able to smell hot hydraulic fluid?

thanks
shawn

It's not the fittings that lets the air out-it's the seals in the cylinders. The air get's compressed and sneaks by the seals, the hydraulic fluid is thicker so it cannot get buy them.

Smelling hot hydraulic fluid is not normal...You have not said but I will assume your backhoe is powered from the tractor? I think I might suspect a bad or improperly seated QD (quick disconnect) that is causing a restriction to the hoe-and is also heating up the fluid. You could try to see if any of the connections are hotter or "vibrate" while the tractor is running.

 

[Brad_Blazer]

The air should just circulate through the system until it gets to the reservoir where it can bubble to the surface.

Chronic air in the system sounds like a suction side restriction.

 

[tommcintire]

My new BH-90X did the same thing fresh from the dealer, with the guy who came out to help me get aquainted with my new tractor standing there. It was the quick disconnect fitting for the supply (or return, not sure which, sorry) from the tractor. It wasn't fully seating. We had to relieve pressure on the line by "burping" it with a hammer & punch in the center of the fitting.

Once we did that, it was fine...

-Tom

 

[80cj]

the backhoe is powered by the tractor.

if air leaks by the seals in the cylinder, then it is still in a dead headed leg and has to travel the length of the cylinder, 10'+ of hose, etc. all DOWN hill. but if there is no hydraulic fluid leaking past the seals, it only has air to push it, so where does it get the force to overcome the boyancy and travel DOWN??? im not trying to be difficult, i just dont understand it.

i havent checked the QD's. i have only had it off once, but didnt really notice any difference before or after. aside from trying to 'burp' it with a hammer then see if that made a difference, how can i tell if the QD is seated?

thanks
shawn

 

[Brad_Blazer]

Basically the volume of the hoses is small compared to the cylinders so air will cycle out of the cylinders. (may take several cycles) Plus the oil will move fast enough to entrain the air and carry it out. Plus.... at full pressure a significant fraction of the air can actually be absobed by the oil. Back in the reservoir at low pressure and velocity the air can come out.

For air in the system due to one-time opening for maintenance or installing a new componet it's no problem. If air or vapor is continuously entering due to a pump intake restriction or similar problem it will cause degradation of the oil and premature wear on the pump as well as the performance symptoms that you describe.

 

[BCLC]

Need Help on a Backhoe Hydraulic Problem.
Have a Power Track LT 450 track dozer and backhoe. Has three control boxes that appear to be daisy chained blade controls > Backhoe Controls > Forward - Reverse controller. There is also a line that goes into the central transmission, kind of complex!
The F-R cylinder quit working, removed it and checked the center seal, replaced the O ring and tested the unit with compressed air. Put it back on the dozer and it would not work moves slightly but very low pressure. Thought it might be the control box in front of the F-R cylinder, or maybe the relieve valve. After $120+ the shop tells me there is nothing wrong with the unit.
Since this unit receives its fluid from the Back hoe box I 'm thinking there may be something wrong in that box or some obstruction in the delivery line. Going to get a pressure gauge and check the flow pressure to see if I can track down the problem. Any suggestions would be appreciated. Love this little dozer works really well but the manual really sucks - lost something in the translation from Chinese into English!!

 

[80cj]

my backhoe/hydraulic problems have not been solved. they continue to get worse. the local dealer is no longer a dealer, so i took it to the next closest dealer. they said that they put gauges on it and it says 2000 psi, so there is no problem. "regardless of what it will or won't do, 2000 psi is 2000 psi, there is no problem"

during the winter, i tried to break up some frozen chunks of topsoil. i couldnt get enough down pressure on them using the teeth on the bucket and had to break them up by hand!

the outriggers do not have enough force to lift the back of the tractor off the ground if the FEL is down. so that means that you can not level the tractor if its on a side angle. the MF/Woods dealer said they talked to Woods and they recommend that you should just let FEL float. (although the manual says differently) i asked them what MF says about having all the weight on the front axle and they didn't know.


does anyone else have a similar setup? am i nuts and just don't remember what it can/can't do? i am thinking that i should have them see what the pressure is on the return side. if it has 2000 psi on one side and still has some pressure on the other side, that would explain this. any thoughts? this has been going on for almost a year and i am just fed up with it all.

thanks
shawn