I need to change the hydraulic fluid on my boom lift to a different viscosity, trying to figure out best way to replace all the fluid. Attached is hydraulic schematic, in the lower left hand section of the drawing I've added the notation "Open Here" and a red arrow next to the pump where I propose to open the suction line. At this point I would put the suction line of the pump into a 5 gal container of new oil and run each cylinder through a cycle while draining the returning oil from the reservoir on the lift. Is there any reason this won't work, or might hurt something?
Can I change hydraulic fluid like this
- Thread starter BeezFun
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Coyote machine
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Why do you need to change viscosity? The schematic shows: 200 bar = 2900.75 psi. Do you really want to crack lines with that level of pressure to push fluid out/suck it in? Who makes the lift? What do they say?
ovrszd
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As you describe it, I don't see a problem at all. Just monitor your source closely so you don't suck air. You aren't at risk of pressure injury at all.
My backhoe holds 28 gallons. The reservoir tank holds app. 8 gallons. If I wanted to completely flush the system replacing old with new I'd have to rig up something similar.
Good luck.
My backhoe holds 28 gallons. The reservoir tank holds app. 8 gallons. If I wanted to completely flush the system replacing old with new I'd have to rig up something similar.
Good luck.
I bought it used from a hot climate, it's colder here.
You're looking at the wrong place on the diagram, the spot I'm tapping into is open to atmosphere.
It's made by Nifty Lift, the shop manual says to do what I'm doing.
Thanks, it's nice to have another pair of eyes for a sanity check.
oldnslo
Super Member
beezfun,
Only concern that I would have is it appears that this is a gas or diesel powered lift so the pump is running anytime the engine is running which means you will always be dumping oil. I suspect this pump will move a few GPM so it will be very easy to run a five gallon bucket empty.
Only concern that I would have is it appears that this is a gas or diesel powered lift so the pump is running anytime the engine is running which means you will always be dumping oil. I suspect this pump will move a few GPM so it will be very easy to run a five gallon bucket empty.
It's actually dual powered, so it can run either off the gas engine, or off the electric motor shown in that diagram directly above the "Engine" as a circle containing an "M". The two power sources are in parallel so in theory I can tap off either. The complication is that the pump that's driven by the DC motor lives inside the reservoir tank, immersed in oil. So it's impossible to get at that suction line. I'm going to stare at the plumbing again and see if there's some way I can use the electric motor because that pump is smaller. If I can't, my plan is to turn the engine on and immediately cycle each of the 3 cylinders. The cylinders are quite large, so I think the fraction of time the engine is running without a cylinder being engaged will be small.
oldnslo
Super Member
Beez
Can you fully retract most or all of the cylinders before starting the fluid change?
If yes this is my suggestion.
Retract all the cylinders. Make the connections like you suggest. Start the engine and extend all the cylinders as far as possible. Shut the engine off. Reconnect the lines as they should be. Fill the reservoir 1/2 to 2/3 full of new fluid and then start the engine and start retracting the cylinders watching so the reservoir doesn稚 over fill. This should remove a vast majority of the old fluid from the system since oil returning to reservoir will be the new fluid.
Can you fully retract most or all of the cylinders before starting the fluid change?
If yes this is my suggestion.
Retract all the cylinders. Make the connections like you suggest. Start the engine and extend all the cylinders as far as possible. Shut the engine off. Reconnect the lines as they should be. Fill the reservoir 1/2 to 2/3 full of new fluid and then start the engine and start retracting the cylinders watching so the reservoir doesn稚 over fill. This should remove a vast majority of the old fluid from the system since oil returning to reservoir will be the new fluid.
Yes, all of them.
Yes, I see, that way none of the new fluid used for extension gets thrown away when I retract.
thanks