BT 900 backhoe problem

[thessler]

Hi
I just bought an L 35 with a bt 900 backhoe attached. The backhoe has problems going left and right. If I hold the lever hard to one side the arm will move to about 45 degrees and then just drift back to the middle even while I'm holding the lever trying to make it stay to the side. It will not go all the way to either side, just about 45 degrees. The rest of the hydraulics work fine, fluid is topped off and it just got a new filter.
My gut tells me it's in the vaulve, or both pistons need rebuild but I think that's unlikely.
Thanks for any advice, Tom

 

[PoTreeBoy]

Hi
I just bought an L 35 with a bt 900 backhoe attached. The backhoe has problems going left and right. If I hold the lever hard to one side the arm will move to about 45 degrees and then just drift back to the middle even while I'm holding the lever trying to make it stay to the side. It will not go all the way to either side, just about 45 degrees. The rest of the hydraulics work fine, fluid is topped off and it just got a new filter.
My gut tells me it's in the vaulve, or both pistons need rebuild but I think that's unlikely.
Thanks for any advice, Tom

I would swap the swing hoses with, say, the bucket lines (at the valve) and see if the problem goes to the bucket operation or stays with the swing.
Make sure you mark the hoses before you move them.
BTW, you haven't by chance had to change bushings and pins on the swing trunnions and cylinders, have you? I need to do mine, but I'm dreading it.

 

[thessler]

I would swap the swing hoses with, say, the bucket lines (at the valve) and see if the problem goes to the bucket operation or stays with the swing.
Make sure you mark the hoses before you move them.
BTW, you haven't by chance had to change bushings and pins on the swing trunnions and cylinders, have you? I need to do mine, but I'm dreading it.

 

[thessler]

OK I swapped the lines with the raise and lower boom lines and the boom acts the same will not swing. So control valves are good.
Does this mean the swing pistons need rebuild?
Kind weird neither one works, is there anything else that effects both pistons?
Thanks for any thoughts, Tom

 

[eserv]

OK I swapped the lines with the raise and lower boom lines and the boom acts the same will not swing. So control valves are good.
Does this mean the swing pistons need rebuild?
Kind weird neither one works, is there anything else that effects both pistons?
Thanks for any thoughts, Tom

Probably just one is bad. they work together so one leaking internally will affect the operation of the other. In this case I would definitely rebuild both though!

 

[thessler]

I'm pretty handy, I'm reading about special tools and special procedures.
Is this something a handy person can do or does it need to go to a hydraulic shop ?
The seal kit alone is 83 per side plus the cost of a face spanner so I don't want to waste that money. But if it's not big deal I'll take it.
thanks, Tom

 

[L35]

I’ve gone through mine with no special tools, not even a spanner. Just a pipe wrench.

 

[PoTreeBoy]

There is a 3pc rod seal installation tool set available on Ebay for about $30. You don't have to use it, but it helps fold up the rod seal.
This probably won't be your last cylinder overhaul .

 

[thessler]

Great, I just ordered the kit.
Thanks, Tom

 

[PoTreeBoy]

Great, I just ordered the kit.
Thanks, Tom

Hints: Loosen the rod gland before you take out the pins that hold the cylinder on, if possible.
Likewise, pin the rod back on the backhoe while loosening the rod nut. That nut will be tight, and it's hard to hold the rod in a vise.
Heat the plastic rings in hot water to soften them before trying to put them on the piston, and be careful not to nick them.
Keep everything clean, and put some oil on the rings, rod and bore before reassembling.
That's all I got. Good luck.

 

[thessler]

I was kind of hoping to rebuild them and not remove the cylinder from the machine. Is that possible?
Thank you for the help.
Tom

 

[PoTreeBoy]

I was kind of hoping to rebuild them and not remove the cylinder from the machine. Is that possible?
Thank you for the help.
Tom

I don't know. Possibly

 

[JonF]

any update on this. rebuilding the cylinders actually fix the problem? im running into the same issue here. rebuilt the cylinders already, so i guess i should prob swap lines and go from there. is that the only 2 possibilities? hoping i wont need a new cylinder by any means.

thanks

 

[GreensvilleJay]

From the description....I'd think the cylinder is leaking( oil bypassing the ram seal )

 

[JonF]

From the description....I'd think the cylinder is leaking( oil bypassing the ram seal )

hoping this will not be to expensive of a fix... what's the chances the actual gland is damaged? wasn't in the best of shape maintenance wise

, when I acquired the tractor a year or so ago. I have slowly been going through, rebuilding each cylinder. The swing cylinder is the only one that did not get better after rebuild... mine swings a tad better in 1 direction than the other., but it seems they both do not fully swing. drift is especially bad when trying to dump the dirt in either direction..

(top picture is current, and bottom is after a good bath & degrease)

 

[GreensvilleJay]

one kit is $43 other is NLA !!! based on serial number of BH. Hope you're number's still on it !!

 

[fried1765]

one kit is $43 other is NLA !!! based on serial number of BH. Hope you're number's still on it !!

Parts are almost always an issue with tractor models 20-25+ years old,...... and relatively few built.

 

[L35]

A good hydraulic shop that rebuilds cylinders may have seals you need if it turns out you fall into the “NLA” serial number bracket.

 

[TheOldHokie]

hoping this will not be to expensive of a fix... what's the chances the actual gland is damaged? wasn't in the best of shape maintenance wise View attachment 114886 , when I acquired the tractor a year or so ago. I have slowly been going through, rebuilding each cylinder. The swing cylinder is the only one that did not get better after rebuild... mine swings a tad better in 1 direction than the other., but it seems they both do not fully swing. drift is especially bad when trying to dump the dirt in either direction..

(top picture is current, and bottom is after a good bath & degrease)

That's a single acting cylinder. What's the problem with swing?

Dan

 

[JonF]

That's a single acting cylinder. What's the problem with swing?

Dan

does not seem to swing full amount in either directions, drifts back to center somewhat. more so going left than going right. i just rebuilt them this summer along with my loader cylinders. did not fix the issue. This issue was happening before i rebuilt the cylinders. at this point im trying to find the time to swap lines around i suppose, try to see if its in the control valves. if so, i found a good rated hydraulic shop 2hrs away that can rebuild it. kits and parts are discontinued.