Backhoe Strange FEL behavior with backhoe attached.

[F_22]

I have a TC33D with 7308 loader and new 757C backhoe. Everything works fine except the loader regenerative (fast) dump. Normal dump works fine but when I go to fast dump position the bucket actually rolls back, opposite of normal. The reservoir is full. Maybe there's air in the FEL bucket cylinders? I haven't been able to exercise this setup cause it's been raining, raining, raining here.

Anybody seen this before or got any insight into what's happening?

Thanks,
Bruce

 

[BadDog]

My bet is your hydraulics are hooked up wrong in the BH itself, or your joystick is defective.

 

[MadReferee]

The fast dump circuit applies pressure to both sides of the cylinder in an attempt to eliminate any air pockets that may form due the the weight of the bucket forcing the cylinder to expand too fast. Now if the bucket is curling up when trying to dump, meaning the cylinder is retracting, then there must be problems with the valve or cylinder that causes little or no fluid to enter the piston side of the cylinder. Thus the pressure on the rod side is overcoming gravity and forcing the bucket to curl instead of dumping.

I vote for the valve being defective since you said everything works ok in normal dump and curl/uncurl modes.

I have a hard time believing that the backhoe installation is causing this problem unless they somehow screwed up the plumbing.

 

[F_22]

I'm back from work and it stopped raining long enough for me to do some testing. (The problem with work is it takes so much time away from operating my tractor!)

I had a few moments of severe self-doubt, but the FEL fast dump does exactly the same thing with the backhoe completely out of the circuit.

Got to check the FEL circuits now. It wouldn't surprise me that it's somehow hooked up wrong since the dealer didn't even bother to torque about half the FEL mount bolts when they installed it. But how could I not have noticed before this? I tried to be surgically clean but maybe some dirt got in and it is a stuck valve.

Actually, I installed the backhoe myself. All the bolts are torqued and I believe the hydraulic hookup is right, at least according to the confusing and incomplete instructions NH provides. While we're at it, what's with this maddening, seemingly random combination of English and metric fasteners and fittings?

 

[F_22]

</font><font color="blue" class="small">( Now if the bucket is curling up when trying to dump, meaning the cylinder is retracting, then there must be problems with the valve or cylinder that causes little or no fluid to enter the piston side of the cylinder. Thus the pressure on the rod side is overcoming gravity and forcing the bucket to curl instead of dumping.)</font>

Excellent information and analysis. Could there be air on the piston side?

I cycled the FEL bucket up and down about 10 times and there's no difference. How many cycles might be required to clear air out? Or is it time required for bubbles to travel back up the lines?

 

[MadReferee]

If you are having no problems in normal operation I don't think trapped air is the problem. You can purge the air by simply holding the valve in each direction until the relief activates. This should purge the lines.

It still sounds like the regen circuit in the spool has problems. If you are under warranty it's time to see the dealer.

 

[F_22]

Problem solved. I had rechecked all the backhoe connections but didn't check the FEL quick couplers. I had been pulling with all my might on the subframe mount bolts right next to them and knocked one loose.

Credit goes to the dealer that sold me the tractor and FEL for catching this one. I obviously should have thought of it myself.

Credit goes to the dealer that sold me the backhoe for finally getting me the correct hydraulic kit and spacers required for my TC33D after only 1-1/2 weeks and me having to drive 100 miles a second time. He originally gave me a DA hydraulic kit (they're different) and required spacers were missing from the subframe kit (NH's fault).

All's well that ends well. I relearned a valuable lesson: Think things through and look for the simple / obvious first.

Thanks for all the help, guys. This is the best tractor forum.

Bruce