Backhoe Strange hydraulic problem with BH75

[wbrkr]

Yesterday, some of my backhoe hydraulics quit working; both stabilizers are OK, and the boom swing is OK. The boom will not extend. When I activate the lever I can hear the tractor engine load up but I get no movement of the boom. After fussing with it for awhile I went back to using the FEL. Later I noticed the boom had retracted fully, actually it retracted more than it does with normal operation and it will not extend. In addition, the bucket will not retract. It will extend however. I have to shut the tractor down, move the lever and manually push the bucket back to retract it, and once moved it just swings loosely. The dipperstick will extend up to a point and then the tractor engine loads up and it won't move further. However, it will retract normally. Very perplexed, any thoughts on the source of my problems?

Bill

 

[jbrody44]

sounds like a possible valve failure to me.

 

[techman]

Sounds like one of the quick disconnect fillings is not fully seated.

Paul

 

[wbrkr]

Well, the BH had been working perfectly and I had it on the tractor for months, using it intermittently with no problems. I took it off today, which was a bit of a challenge since the boom would not extend. The hydraulic connectors looked fine with no indications of a miss seat.
By the way, is it appropriate to connect the hydraulic supply to the return when the backhoe is off the tractor?

Bill

 

[wbrkr]

sounds like a possible valve failure to me.

Any ideas on how to verify that?

 

[jbrody44]

You could possibly try changing the lines around to see if the hydraulic pistons in question would extend and retract as they are supposed to when being driven by the valve that seems to be working properly (the swing). That would eliminate the possibility of sticking hydraulic pistons. This could be messy and you may need some longer hoses etc. The fact that more than one of the rams is acting strangely makes me think it is not the hydraulic rams themselves. The fact that the outriggers and swing hydraulics work correctly make me think the hydraulic pump is putting out enough and the supply and return are OK (plus your fel is working fine, right?) The swing and outrigger rams are however much smaller than the rams on the boom etc and should need less flow to operate. Do you hear the pressure relief whining when the motor loads up? You could possibly remove the valve(s) and see if you dealer would test them for you.

 

[wbrkr]

The fact that more than one of the rams is acting strangely makes me think it is not the hydraulic rams themselves. The fact that the outriggers and swing hydraulics work correctly make me think the hydraulic pump is putting out enough and the supply and return are OK (plus your FEL is working fine, right?).

Yes, the FEL works normally and the stabilizers work normally and easily lift the tractor.
I have been puzzling over this issue quite a lot and thinking of what has changed and the only thing I have come up with is the weather is warmer. I'm not sure that is relevant since active use causes the hydraulics to warm up anyway. I will try to reinstall the BH this evening and then try it out first thing in the morning (it is forecast to go down near freezing tonight here).
The other issue I wanted to mention is that I had a hydraulic leak last fall. It was simply a fitting that had loosened and caused a leak. After tightening the fitting I refilled the hydraulic reservoir. I have a terrible time using the sight glass to determine if I have added enough fluid. First of all, I cannot tell whether the fluid level is fully below the sight glass level or fully above. On a sunny day the glare makes it very difficult to even see the sight glass. Well when refilling the reservoir, I would add some fluid, stop, go look at the sight glass and then add some more fluid. The bottom line is that I filled the reservoir to the top without realizing I was over the sight glass. Although I drained a bunch out, at this point I don't know if I have too much or too little fluid in that reservoir and I do not see a fluid line in the sight glass. Any ideas on how to determine if I am low or high on the fluid level (without using the sight glass!!). Thanks for any thoughts on these issues.

Bill

 

[jbrody44]

on my l3400 hst. the sight glass background is white when the fluid is low. if it is high it will be a yellow color. when level is right you will see half white half yellow,.

 

[wbrkr]

on my l3400 hst. the sight glass background is white when the fluid is low. if it is high it will be a yellow color. when level is right you will see half white half yellow,.

Thanks, then I still have too much hydraulic fluid.