Hydraulics won't hold

   / Hydraulics won't hold #1  

arcamm

Member
Joined
May 6, 2009
Messages
32
Location
Mt Airy MD
Tractor
Gravely
I just picked up a Terramite Model 1 backhoe. The out riggers will not stay up or hold the tractor when lowered. There are no external leaks, so I'm assuming everthing is internal. Where should I start looking? Would it be the pistons in the cylinders or the spoolers?

Thanks, Ron C
 
   / Hydraulics won't hold #2  
Troubleshoot with a pressure guage or start with the pistons.......the piston seal inside is probably worn and bypassing.....you won't see any oil leaking if it's the internal piston seal......
 
   / Hydraulics won't hold #3  
If the relief for the BH does not activate with the cyl are fully extended or retracted, then you have a leak in the cyl as wdchyd mentioned. Remote possibility could be a worn outrigger spool, but unlikely. Are both outrigger cyl doing the same thing?
 
   / Hydraulics won't hold
  • Thread Starter
#4  
Yes, it's both cylinders are doing the same thing. I suspect some of the others are as well, I just got it running yesterday. The machine was setting for quite a while.
 
   / Hydraulics won't hold #5  
How many times have you cycled the outrigger cyl. Do they totally collapse or feel spongy?

Cycle them about ten times and see if there is any difference.

I would suggest a hyd gage and test all the cyl.
 
   / Hydraulics won't hold
  • Thread Starter
#6  
They have been moved up and down atleast that much, but I will run them through 10 full cycles to make sure. They will lift the tractor, but they bleed down in less than a minute.
 
   / Hydraulics won't hold #7  
I would look in the valve block for a broke load valve spring or something.
Even if the cyl piston seals leak,the legs should hold in the push downstroke.And slip back just a little till the pressure is equal on both sides of the piston when you let go of the lever,they'll just extend slower due to bypass to the return side.
 
   / Hydraulics won't hold #8  
You never did say if the relief valve activated at full extend or retract. Any idea what the BH relief valve setting is?

You could add a needle valve to the extend cyl hose. and raise the outriggers, then tighten the needle closed, and see what happens.

That should lock the fluid in the base end. If the cyl leaks sown, it is for sure, bypassing.
 
   / Hydraulics won't hold
  • Thread Starter
#9  
I'm guessing it does. I'm basing that on the engine not dead heading when the piston reaches the end of the stroke. No idea what the settings are.

They will hold position as long as I have the lever pushed, but as soon as I release it, they start to bleed off. Both side act the same and bleed down a pretty much the same rate.
 
   / Hydraulics won't hold #10  
This Model 1 Terramite is from between 1965 to 1972....cant find a good picture of it online....

Main relief is not in the picture when outrigger cylinder is bleeding down. Control valve in neutral makes work ports closed.

If piston seal is leaking and capped side holds the load, cylinder rod is retracting and that rod volume of oil must be displaced through the control valve, if there is no external rod seal leakage. Only an eventual work port relief, or spool could leak. If piston seal is leaking, pressure will equalize on both sides of piston.

Bleed down in one minute do not tell the entire story...diameter size of rod and how long retract will determine leakage volume....

OP should also make sure this old control valve really sets in the real neutral position, maybe it is sticking a bit and not closing the work port properly...spool stiction from rust etc could cause bleed down too....if spool is 1/32-2/32" off from neutral could be enough....
 
 
Top