Backhoe Kubota B20 with BT750 backhoe: Auto Return feature

[goeduck]

Note that the B20 has 2 hydraulic filters, and I will flush and drain first, replace the filters, then add THF. There will still be some water in there, but a lot less.

My B21 has 2 filters and a strainer. The strainer was a bear to get out and when I finally did, it was as clean as a whistle. But my fluid was good looking, not like yours. I just wanted to start off fresh when I bought it used at 1700 hrs so I changed everything.

 

[Smokeydog]

On my B20 had two rear facing case drains also. The dealer didn’t know or use them. They were in the manual.

As you can see the hydraulic/transmission fluid is good at collecting water in suspension. I would caution against using anything else. Not worth the risk on seals, metal parts and filter media. Just going to have to flush, change filters several times and find your leak/in-leakage problem.

Mine did not have the auto return feature. A friend of mine B20 did. He got his working, but he is Electrical engineer that enjoyed playing with electrons. We have both since moved to B26s.

The steering box on the B20 is susceptible to rain water intrusion and displaces the oil and ruins the bearings. Simple fix if caught early.

 

[dfkrug]

On my B20 had two rear facing case drains also. The dealer didn稚 know or use them. They were in the manual.

Yeah, the manual shows FOUR drains for the sump, two in the rear case, and 2 on the side, amidship. Mine only has ONE of the rear case drains and the 2 amidship in the mainframe. I have not found the inlet screen yet, but I am replacing the inlet hoses.

The parts book also shows 2 different BT750 models, the BT750AR, and the BT750B. Mine is the latter model, but both show the Auto Return feature.

The purpose of the elixer I mentioned is to help rid the case of suspended water, not as a long term fluid. My recent B8200 project was just as bad with the emulsified water problem.

I will look into possible water intrusion sites near the PS valve. Thx for the suggestion.

 

[dfkrug]

I just got the Kubota Owner's Manual for the BT650 and BT750, and it answers most of my questions. I will post the wiring diagram and pertinent text here so that future queries about Auto Return can be answered.

I still wonder if the 2 large solenoid valves are actuated proportionally, or are they full ON or OFF. A simple potentiometer seems to provide position feedback, and the missing switch on the console seems to turn ON and OFF the end-of-swing return only.

We shall see once I get the tractor running again.

 

[dfkrug]

Here is the Big Failure of this B20. I thought it was a leaky 30yo hose inside the boom, but it turned out to be shredded gland seals in the boom cylinder. And THAT was caused by several corrosion spots on the rod, one right where the seal would be when in the locked UP position.

Three choices on the repair: 1) buy a new rod from Kubota, listed at $461 + tax and shipping. Maybe $550, delivered. 2) buy some plated or stainless steel 35mm rod stock and fabricate a new cylinder rod. Welding and drilling/tapping required. 3) grind and polish the corrosion spots, and reassemble with new seals.

I am tempted to do #2, which is what I would do if this hoe were mine and needed to be as good as new. Problem is that a quick search for plated or SS rod stock shows I would likely have to buy SS, and that would be about $250 for the a 3-ft piece.

So, #3 it is. Pix show one of the repaired spots, before and after repair. The 'before' photo is after wire-brushing, but before any filing with a diamond file. I still may burnish or polish a little more before reassembly.

 

[Gator6x4]

Here is the Big Failure of this B20. I thought it was a leaky 30yo hose inside the boom, but it turned out to be shredded gland seals in the boom cylinder. And THAT was caused by several corrosion spots on the rod, one right where the seal would be when in the locked UP position.

Three choices on the repair: 1) buy a new rod from Kubota, listed at $461 + tax and shipping. Maybe $550, delivered. 2) buy some plated or stainless steel 35mm rod stock and fabricate a new cylinder rod. Welding and drilling/tapping required. 3) grind and polish the corrosion spots, and reassemble with new seals.

I am tempted to do #2, which is what I would do if this hoe were mine and needed to be as good as new. Problem is that a quick search for plated or SS rod stock shows I would likely have to buy SS, and that would be about $250 for the a 3-ft piece.

So, #3 it is. Pix show one of the repaired spots, before and after repair. The 'before' photo is after wire-brushing, but before any filing with a diamond file. I still may burnish or polish a little more before reassembly.

If available a 1.5" -2.0" wide CROCUS CLOTH belt approximately 2 foot long would work great for polishing. Form a loop around the rod and pull on each end of the crocus cloth belt while maintaining contact pressure on the rod with the crocus cloth belt will produce a mirror like finish.

 

[Carl_NH]

From the pics there are some deeper pits on the shaft. A few years ago some rocks dropped on the stabilizer shaft nicking them and I cleaned up the nicks, cleaned with solvent, then filled the few small depressions (size of a pencil lead) with JB Weld then sanded smooth with 800 crocus as Gator mentioned and then polishing compound. So far so good.

I would not want to fill deep voids this way but for your case this might work.