Spool valve removal

otter

Member

Equipment
L3800, LA524 loader, BH77 backhoe, thumb, box blade small wood lot log grapple
Sep 26, 2014
52
3
8
Chase, Alaska
While sorting out a fail to lift 100% boom function 100% of the time on a BH77 on a L3800 (that has been an on going issue) I have removed both relief valves and the diverter (behind the bolt between the two fluid lines for the boom valve)for inspection, cleanng and reinstalled them. The push pins on th relief valves worked well.
Next is the spool valve but I do not know how it is removed from the block. I***8217;ve removed the linkage to the control handle and the cover plate held on by two Allen bolts but can not get the spool removed by lifting straight up or un-threading (I***8217;ve counted my rotations should it need to be turned back to original position) the valve.

Do i need to remove the diverted valve (between the fluid supply/return lines) or ........?
I have the WSM but can find no solution there.
Hopeing to NOT remove the entire valve block to inspect/repair/replace the valve.

Any insite would be helpful.
Thank you
 
Last edited:

lugbolt

Well-known member

Equipment
ZG127S-54
Oct 15, 2015
4,808
1,575
113
Mid, South, USA
Simple stuff first.

Does the boom drop quickly when engine is off? That would point to-most likely-an internal cylinder problem.

The valves aren't known for issues. Occasionally a safety valve will have a tiny piece of trash on the o-ring, but that's uncommon. Quite uncommon actually.
 

North Idaho Wolfman

Moderator
Staff member
Lifetime Member

Equipment
L3450DT-GST, Woods FEL, B7100 HSD, FEL, 60" SB, 743 Bobcat with V2203, and more
Jun 9, 2013
28,306
4,858
113
Sandpoint, ID
Second what lugbolt said.

Have you tried swapping lift and roll and see what you get?
Have you tried swapping the quick disconnects on the lines?
 

otter

Member

Equipment
L3800, LA524 loader, BH77 backhoe, thumb, box blade small wood lot log grapple
Sep 26, 2014
52
3
8
Chase, Alaska
LB and NIW
Thank you for the information and suggestions.
Will switch lines on controls to see the results.
 

otter

Member

Equipment
L3800, LA524 loader, BH77 backhoe, thumb, box blade small wood lot log grapple
Sep 26, 2014
52
3
8
Chase, Alaska
Two leak down tests were completed; the first was overnight with a drop from 4 inches to hard on wooden blocks. The second is ongoing today with a 4-3/4 inch drop in 4 hours. I wanted to gage how much it drops per hour so the test has 5 inches until its hard down on blocks again. Its checked every two hours or so. You can not see the boom drop. No sudden drop with slowing afterwards.

Swapping out supply and return runs with another joy stick function is pending this leak down.

The reason I thought it would be a valve/pressure relief issue is how the boom would suddenly drop while digging after operating normally, then return to operating normally again-until it wouldn’t. The more the hoe was operated the more frequently it would suddenly drop-seemed to be a valve opening-but I am a rookie with hydrostatic drive and implements and going off operating function.

There is no hydronic oil leaking at any fitting or cylinder.

Thanks again for the assistance. Its great having the expertise and knowledge available in the Forum.
 

otter

Member

Equipment
L3800, LA524 loader, BH77 backhoe, thumb, box blade small wood lot log grapple
Sep 26, 2014
52
3
8
Chase, Alaska
Following up should anyone develop the same issue.
After getting great suggestions the safety relief valves were removed and cleaned a second time.
Reinstalled on the valve assembly and taken out to test by digging two birch stumps out.
Worked great!
I suspect there was a piece of junk obstructing the relief valves correct functioning.

Thank you for the help and suggestions!