Loader Hydraulic valve problem

[ozarkbru]

On my B7800's loader the bucket will float down but not power down.
Last weekend while using my backhoe I was lifting the front end a lot over a few hours, after that I did some some loading and back dragging then trouble started, it would not lower with pressure. The valve was hot, Both white and yellow lines appear to flex under pressure but all other positions work well.
, check valve?

 

[KWentling]

If it will go down when in the float position that about eliminates anything like an unseated QD or mechanical binding. Are the yellow and white lines the raise and lower lines or pressure/return lines supplying the valve ( or some other combination)? I don't know for sure but I would think load check valves would have to be OK for the float to work. You get no down movement at all under pressure? Does the valve go over the pressure relief when held in the down position? Pretty much has me stumped at this point. Maybe a nut has come off one of the cylinder rods and the piston is free? You might try pulling hoses off the cylinders and sticking them in a bucket and check for flow. Make sure the loader is down or supported before taking any lines loose.

Kim

 

[CHDinCT]

Not familiar with the B7800 but a common trouble shooting step is to reverse the lines from bucket curl/dump and boom raise/lower to see if the problem moves with the line change. If it does, the issue is likely in the valve, but if not, the restriction is likely in the raise/lower circuit somewhere. Also, a lot of these issues are solved by removing and reinstalling the quick connects. Sometimes they seem seated, but are not fully, which could cause the symptoms you had before it went fully dead.

 

[ozarkbru]

Both replies gave good ideas to try, thanks I'll be sure to let you know the results.
Bruce.

 

[tr11439]

Another common problem is that people tend to use Teflon tape to seal the threads. Teflon will break down and cause restrictions within the system. Make sure that you use a liquid sealer. Loc-Tite makes a good one.

 

[oldnslo]

+1 on the QD"s not being seated or worn slightly. Floating down there is limited flow and pressure.

Powering down gives higher velocities which can cause the check's in the QD"s to seal and if it is the return line both hoses would stiffen from pressure.

Roy

 

[ozarkbru]

Thanks for the replies,
Just got done swapping hoses and watching what was going on, when pushing forward both lines off of the white and yellow ports (bucket up and down) are under pressure, where the white line should be exhausting, it is not.
Does any one have a schematic of this valve? I'll probity have to go to Kubota for the parts any way.
Bruce.
The speck book for the LA402 doesn't include port info.

 

[oldnslo]

If are looking for a parts break down for the quick disconnects (QD) I don't think you will find one. About the only item replaceable on them is the O-rings. If the QD is bad replace it. You just have to figure our which half is at fault.

Does your QD have ball or poppet style seats in them. If poppet style look at the poppets to see if one of them appears wore down so it protrudes less than the others.

If the QD's are not original some one may have put on a ball style nipple with a poppet style coupling. This will work for awhile but will eventually cause the problem you are describing.

Roy

 

[7800DUDE]

make sure your 3 pt hitch lever is not engaged so times that happens

 

[ozarkbru]

make sure your 3 pt hitch lever is not engaged so times that happens

That's interesting, Too late to check it out but I know the problem has nothing to do with the QD's.

 

[ozarkbru]

7800DUDE got it! I'll the years I've owned that tractor I never noticed it did that, sure glad I didn't start digging in to that valve.
Thanks for the help.
Bruce

 

[Henro]

Hi All,

I used to be a regular around here...hello to those who remember me!

Anyway, this thread saved me A LOT of time and aggravation...so it gotta be worth something to bump it up for others to see and remember.

Last week I topped off the hydraulic fluid in my B2910, with just under 1,000 hours on it, and afterwards the loader would not lower just like the OP's would not.

Float worked. Swapping hoses made the loader go up when the joy stick was pushed in the down position... but it would not lower even then when told to go up (with the hoses still swapped). Float still worked, causing the loader to go down (swapped hoses or normal).

I found the bucket would power down if I curled it at the same time. Either direction of curl.

Nothing made sense. I do have a fair understanding of hydraulics... I changed the four quick disconnects just in case. Made no difference.

Then I read this thread!!! Lucky me!

I had just put my backhoe on before topping up the hydraulic fluid. For whatever reason, after hooking it up, instead of lowering the 3PH as I always do, I must have pushed the handle in the wrong direction and it was trying to lift the hoe, and which is an undesirable thing, and something none of us would do intentionally. The effect of this, for whatever reason, is that the loader will not lower in this state of affairs, even though it will go up and the bucket curl will work in both directions. AND the loader arms will power down when the bucket is curled!

So...after reading this thread, I ran down to the shed and found my 3PH lever in the full raise position with the backhoe on. Put it in the correct full down position and BINGO! Operation is now normal and the loader powers down and up as it always did.

So all you 3PH backhoe owners...put this one in your memory banks!!!

7800 DUDE and the original poster...many thanks to you guys!

This beer is for you! And the next one too... :licking:

I really can't thank you guys enough!:thumbsup:

I feel like a really happy camper at the moment...no...I AM A REALLY HAPPY CAMPER!

Whoo Hoo !!!

 

[BlacknTan]

Hi All,

I used to be a regular around here...hello to those who remember me!

Anyway, this thread saved me A LOT of time and aggravation...so it gotta be worth something to bump it up for others to see and remember.

Last week I topped off the hydraulic fluid in my B2910, with just under 1,000 hours on it, and afterwards the loader would not lower just like the OP's would not.

Float worked. Swapping hoses made the loader go up when the joy stick was pushed in the down position... but it would not lower even then when told to go up (with the hoses still swapped). Float still worked, causing the loader to go down (swapped hoses or normal).

I found the bucket would power down if I curled it at the same time. Either direction of curl.

Nothing made sense. I do have a fair understanding of hydraulics... I changed the four quick disconnects just in case. Made no difference.

Then I read this thread!!! Lucky me!

I had just put my backhoe on before topping up the hydraulic fluid. For whatever reason, after hooking it up, instead of lowering the 3PH as I always do, I must have pushed the handle in the wrong direction and it was trying to lift the hoe, and which is an undesirable thing, and something none of us would do intentionally. The effect of this, for whatever reason, is that the loader will not lower in this state of affairs, even though it will go up and the bucket curl will work in both directions. AND the loader arms will power down when the bucket is curled!

So...after reading this thread, I ran down to the shed and found my 3PH lever in the full raise position with the backhoe on. Put it in the correct full down position and BINGO! Operation is now normal and the loader powers down and up as it always did.

So all you 3PH backhoe owners...put this one in your memory banks!!!

7800 DUDE and the original poster...many thanks to you guys!

This beer is for you! And the next one too... :licking:

I really can't thank you guys enough!:thumbsup:

I feel like a really happy camper at the moment...no...I AM A REALLY HAPPY CAMPER!

Whoo Hoo !!!

I remember you Henro!

You and some of the other old regulars gave me good ideas, and helped me alot with my B-7800 ..

I hope you stick around awhile!

 

[teg]

:thumbsup::thumbsup::thumbsup: Glad you see you back!!! Anyone with two beers in hand... is a friend of mine!!! Glad to see you remembered your password after ~1.5 years :laughing: