Backhoe Backhoe slowly going down?

[Stef]

What would be a normal delay before my backhoe (BH75) touches the ground (relax) when the tractor is not used?

My experience on that subject is related to my former BX23. I could leave it in a corner of the driveway for a couple of days without the boom lock pin engaged and the backhoe would have moved just a bit without touching the ground.

Now with my BH75, one night is enough for it to completely lay on the ground (without the boom lock pin of course). Ok, so far it's not too annoying. But the problem is when I'm working with the tractor and the backhoe is on. I have no choice but to put the lock pin in because it touches the ground too fast for me to work for a couple of hours with the tractor.

And... I'm not sure anymore that I have full strength when I curl my bucket (BH75) . I'm supposed to have a maximum digging force of 3339 pounds with the bucket, but I jam even when I'm digging in compacted sand. So I'd like to know if my dealer can test it in order to see if the correct hydraulic pressure is going where it should be?

Thanks guys for your opinions.

 

[wushaw]

I would hope you dealer has the capability to put a pressure guage on to verify the proper pressures and fix what is wrong.
Good luck and keep us informed, I also have a BH75 that is still going strong since curl cylinder replacement (bent)recently.

 

[ronjhall]

My 4690 BH will drop a couple of inches every hour whether tractor is running or not. I have gotten into the habit of pulling on BH controls every half hour or so when doing work with FEL and BH is on tractor.

 

[tawilson]

My NH 758c drops so quickly I've gotten in the habit of putting the transport latch on it every time I get on and off.

 

[Bob53]

I have the B3030 with same Hoe and Fel, hoe drops to ground over night since I got it. I questioned this also early on, and another memeber that had same setup did the same. If i go long distances and bumpy i always use locking pin because hoe drops some. Dealer told me this should not happen when operating, ovenight is normal. Dealer checked it out though and told me it did not drop for him, which i guess he just drove it around shop some , so i pretty much just leave pin in unless i'm using hoe and not annoying anymore.
Other than roots or rocks really does not hangup much in digging. One time the hoe did start to get real slow though, but it was just the nuts coming off the manafold where the levers attach to it. And if i just continued the bolt would come out and could not operate clylinder at all. This has happend 3 times so i used some locktight.

 

[KubotaOne]

I have the same set-up as you Stef.

My BH drops quickly, it would probably be on the ground in the morning. I use the locking pin all the time now. Even when I'm moving I use the pin to relieve stress on the cylinders, specially over the bumpy stuff.

As far as power - I haven't noticed any reduction.

 

[AntrimMan]

Stef,
regretfully the backhoes we have purchased are not the perfection we anticipated. Maybe we expected too much.

The length of time required to sag will depend on a number of things leaking. The biggest suspect is the piston seal. I know the difference between superior and inferior design and the cylinders on the BH90 are toward the lower end of the scale. I suspect the BH75 is identical but for size. The piston seal is comprised of a rectangular cross section PTFE ring sitting on an o-ring. The o-ring applies diametral squeeze to force the seal out against the cylinder wall and to seal itself against the piston land. The inside finish on the cylinder walls is made by the skive-burnishing process. The tool cuts (skives) the diameter on the way down the tube and then roller burnishes on the back stroke. It's a common tube finishing practice. There are two types of skive-burnishing machine feeds. If the feed on the skive-burnishing machine is not mechanically actuated there will be surges in the feed rate caused by the machine hydraulics and a resulting undulation in the cylinder wall finish. The BH90 cylinders have undulations in the wall finish. Everthing points to an economy grade of cylinder as far as piston seal and wall finish is concerned. The rods are double sealed and one of the seals is a u-cup. I don't see the rods leaking anytime soon.
My next machine will have u-cup seals on the pistons. I see Cat's and Deere's with the hoe's staying up in place on an unused machine for long periods of time. I bet they use u-cups on the pistons.
Bottom line is the way the cylinders are internally sealed causes much of the sag you see. Manufacturing tolerances will cause the time period to vary. Get used to leaning back and pulling the levers.

Also suspect is the valve stack. There would be no practical reason to match a gem of a valve to an economy cylinder. I'm sorry this all sounds so negative but it is reality.

I also think I'm losing the bucket force. I haven't conjured up any particular reason as yet or a real easy way to tell if I'm just imagining the loss.
I seriously doubt the dealer can actually measure the bucket digging force and provide a number. He can measure hydraulic pressure at the cylinder ports to see if all is within spec's. I doubt if he can do a cylinder leakdown. I can't find any published specs for leakdown in terms of load applied versus rate of decline, it's a little too complex for the average owner to perform anyway. If there is an internal leak you may hear a squeal as the pressurised oil passes the seal. Hold the lever in postion and have an associate listen to the cylinder. Be careful.

What you haven't discovered yet is the side loading applied to the cylinders because of pin bore manufacturing issues. This won't help matters any in terms of longevity.

Please keep us posted as to your progress with the dealer and the area rep regardless of the outcome.
All the best,
Martin

 

[Volfandt]

Altho I don't have a BH75, I do experience similar leakdown on my BX23's BH.
When it was brand new, in the winter, it would stay tucked up & away for weeks at a time without dropping. I really didn't notice it dropping down until after I did the 50 hr., which was this summer. Now since it shipped w/SUDT, putting in new SUDT shouldn't have made it happen. So I tend to think that in my case it may be a combination of seal wear as well as the fluid be thinner in these hot temps. I guess I'll know if this is correct come winter.
Oddly enough, it certain positions, the FEL will drop too. Seems the lower I stow it, the more likely it'll drop.

I've yet to notice the 60" MMM dropping any.

While the tractor has about 85hrs on it, the MMM has about 65hrs, the FEL perhaps 35hrs & the BH only has about 20hrs of working time on it.

FWIW, Volfandt