Backhoe Cylinders Extend Only

[mng]

Hello,

My latest problem is an interesting one.

I recently purchased a used Wallenstein GX 700 back hoe and it has been good for us so far, except for a few leaking hoses which I promptly replaced.

The last hose that I replaced was a different story. Once all the work was complete I plug the hoe back in to the remotes on the tractor and the all cylinders only extend in a very erratic and jerky fassion, I can not retract them at all. I took the new hose apart to check for obstructions and I couldn't see anything obvious.

It seems like one of the hoses going to the tractor has no pressure into it. I did try switching the hoses and the problem persists.

Thanks for your help
Michel

 

[wdchyd]

Michel,

check your quickconnects, seems to possibly be return restriction going back to tank...if you changed a few hoses double check your hookup (maybe two hoses mixed up by mistake)....the last hose you took apart to check you need to blow out with air (maybe overcrimped?)...

definitely check those quick connects real close.....if they are not snapped in good they become a check valve real quick....

 

[David-Davies]

Hello mng, It sonds like you have air in the system. Run the tractor at eighteen hundred RPM. Exstend and retract all the cylenders on the tractor bucket, to see if they work properly, Then do the hoe one cylinder at a time, be slow so you don't get air in the oil when it returns to the tractor housing.
David-Davies

 

[mmurphy]

And how is oil level??

 

[bindian]

I agree with wdchyd. The disconnects can be physically connected, but not hooked in good enough to make a connection. I had the same problem you are stating and it turned out to be a quick disconnect popped off just enough to close the ball.
hugs, Brandi

 

[J_J]

If you had a hyd gage in the system it would help trouble shoot everything hyd.

 

[mng]

Hello,

Thanks for you replies, I did check the oil level and it is fine. I can see how that would cause the symptoms I'm seeing. I will focus on the quick connects this evening and make absolutely sure that they are connected properly. If this doesn't fix the problem I will replace them.

I'll keep you posted on the results


Thanks
Michel

 

[wdchyd]

If you had a hyd gage in the system it would help trouble shoot everything hyd.

Excellent advise:thumbsup:....we generally use pressure guage/flow meter set up at first sign of trouble....saves alot of time tho not cost effective for DIY repair for some tractor owners...

I always think of Elec troubleshooting as similar to hydraulic troubleshooting...in elec troubleshooting without a Volt/ohm/amp meter you are only guessing whats going on inside that wire....in hyd troubleshooting without Pressure/flow meter/load valve you are also guessing whats going on inside that hose/cyl/valve/pump ect.....

So Yes, the Pressure Guage is essential (sorry JJ, you said it much better than my yakking):newhere:

 

[wdchyd]

I agree with wdchyd. The disconnects can be physically connected, but not hooked in good enough to make a connection. I had the same problem you are stating and it turned out to be a quick disconnect popped off just enough to close the ball.
hugs, Brandi

Had one job years back where cust brings in plow....b4 starting up, did a walk around....1 QC didn't look right....a look inside with flashlight found small rock inside female QC (probably 3/32 in dia)....picked it out with pocket screwdriver and VIOLA....

Customer got quote for $375. fix the day before from others:confused2:, he only brought it in to us for 2nd opinion.....N/C.....Customer For Life!!!!

 

[mng]

Hello All,

For starters the problem is fixed, Thanks to all who helped.

A bit of background first.

When I replaced the last hose, the back hoe was not mounted to the tractor, While mounting shortly after I got some erratic behavior (Likely because of air in the hose) and the BH dropped some causing one the hoses attached to the tractor to snag and disconnect. I didn't think any thing of it, it fell out I plugged it back in, why is my BH not doing what I want it to??

It turns out that it was the return hose, the one with the check valve on it. This caused the pressure in that segment of the hose (between the check valve and the quick disconnect(QD)) to remain at a high level. When I plugged the hose back in there was to much pressure in the hose for the little ball at the end of the QD to be pushed in.

While I was running the tractor afterwards thinking that everything was ok with the QD oil would come in but could not leave, only allowing me to extend the cylinders.

The fix was simple, slowly unscrew the quick disconnect on the pressurized hose to pressurized it, reinstall the QD with new teflon tape and there you go, a BH that works.

I also got one of the cloth sleeves to run both of the hoses from the BH to the tractor in such that they are less likely to snag.

Once again thanks for the great advice, and for directing me away from the new hose and to the actual cause of the problem.

Michel