iDRY Vacuum Kilns


1989 LT40 hydraulic Valve and Switch

Started by Chiselbut, May 08, 2024, 02:50:44 AM

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See reply below. Apologies for the confusing reply.  Typing on a phone with fat fingers takes patience

doc henderson

chisel, if you are answering or commenting on a recent comment, you do not need to quote it.  only if it is so far behind that folks will not understand.  you can mention the name of the poster, and we can look back.  also, if you quote, try to put your comment below and not in the quote, or it looks like you quoted without any comment, until we read the quote.  Minor details.   :thumbsup:  Doc.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor



....those threaded holes are for the 7/16 - 24 screws that hold the valve assembly together from the back.  I suspect some fluid was leaking into the threads.  The hydraulic function was not impacted, but over several months or more i can see how things became oily inside the hydraulic box with a slow drip...the threaded hole is  around the 7 o'clock mark if that matters

...  I looked over the lever spring, actually disassembled the entire valve removing the lever and spring.  It was good... tight, good spring action when reinstalling - lever works as it should.  In regards the hydraulic valve nut... i just turned the entire valve placing a 3/4" wrench on the nut at the manifold- and turned it out less than 1/4 turn. ...

Re. Electric issue and burning wire: ....haven't gotten to the bottom of the issue just yet.  All of the contacts  (everwhere on the mill) including the hydraulic solenoid were rusted, some loose, all wires are beginning to show discoloration/oxidization from moisture, crimps frayed or near breaking off.  There was a 14 AWG from the variable speed box for the back and  forward control (PCB?) (im doing  this from memory...) that was spliced into a 6 gauge negative batt terminal wire.  Didnt seem correct. I followed the wiring diagram and the  back of the PCB has two posts, one larger in diameter than the other post (diagram shows white wire spliced into neg batt terminal wire). That 14 gauge wire  had excessive melting and i am replacing it with a matching 6 gauge wire.  Still need to bury my head into the wiring, old wires etc and replace.  One step at a time.  New hydraulic solenoid, wires and connectors now.  That cant hurt.


Looking back at the pictures of the hydraulic unit, it sure looks like it is one manufactured by Monarch. 
Change is hard....
Especially when a jar full of it falls off the top shelf and hits your head!


Yes.  It is a Monarch now i believe owned or bought out by a German company- Bucher

doc henderson

If you have a voltage drop due to all the above, it will naturally increase amperage in the wire as it is used.  most connectors are nonferrous but may corrode or oxidize and not make good contact.  di-electric grease can help.  It does not conduct, so it is to protect those connections, is my understanding.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

Ben Cut-wright

The lever springs are prone to break at the severe bends where the stress is focused  They just fatigue, don't give a warning.  If these haven't been replaced in one while this would have been the best time.

The hydraulic "nut" below the valve holds the valve onto an adapter that screws into the manifold.  "turned it out less than a 1/4 turn" would mean you didn't break the nut loose to rotate the valve?  The threaded portion of that fitting which screws into the manifold is better left alone. If you did turn it, be sure it doesn't begin to leak.  I prefer to tighten the nut enough to hold the valve secure enough to connect the plumbing.  Then finish by tightening the nut properly.

The other control valve mounting nuts you describe as rounded off could have been easily *replaced while you had the entire assembly removed. As I mentioned previously, those are prone to freeze and then get rounded off when someone tries to remove them.  That nut is part of a four piece assembly.  When the nut is over-tightened onto the bottom piece it deforms the sealing ring. That wedges the nut and is often impossible to remove.  Cutting the nut is the easiest method I've found, and least likely to do damage. This will permit the valves to be readily removed at a later date instead of requiring a lengthy downtime. 

Where did you get the capacitor specifications? The purpose of that capacitor is to keep the high (er) voltage spark from the valve switch opening from going back into the wiring. That's why it's good to check all of them.

Might have missed you saying, did you check the brushes in the pump motor while it was off the mill?


You have successfully shown more experience than i ever can or will.  My intent for the hydraulic manifold portion of this sawmill project was to regain toe board operation and share that process.  I didnt go into this hydraulic valve repair to do a complete overhaul of the valve assembly.  While  there is merit in doing that;  by removing all of the valves, replacing all lever springs, replacing rounded over nuts, and checking brushes  etc that isn't my intent at this time as the rest are functional.

You make a good point to address potential issues now; no one can argue that.  Yet to be honest, I regret starting this thread and feel somewhat dinged after adapting and changing the format as this saw mill project grew; participating, criticized addressing your questions by finding fault in my attempt to be helpful and by sharing and going into this repair apparently naively.  This posting has become way too intense, and I am finding myself justifying this more than this post was intended as a fun and enjoyable endeavor.

May I suggest that with your skill and experience that you take the initiative, be more proactive, less critical, and write, share, and illustrate these repairs for others to find on the internet.   It's apparent that I stepped into an area of sharing above my pay grade given my skill and experience.

Ben Cut-wright

@Chiselbut said:

"but  its best to adapt the project to a more thorough rebuild.  what has developed from singular repair and technical questions has morphed to a change in approach"

This is your thread. If you wish to only share "how you did it" with less input I can certainly accommodate that.


Maybe  I missed it but is the toeboard function  working? As stated earlier, I have the same setup and appreciate everyone's input and tips. Thanks 

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