Hearing a whine from my 520H hydraulic lift

[Gary S Minnesota 51]

Hi All,

Late last summer I changed the transmission oil (10W-30) on my new to me 520H.  Since then I had driven it a few times but had not used the hydraulic lift until I recently when I mounted the single state snow blower.  Now when I raise the blower and/or operate the lift lever I get an occasional loud whine.  If I lower the blower to the ground the whine ceases.  If I stop it Mid way in the up/down travel I hear what sounds like a hissing sound.  Wiggling the up/down lever alters the hissing sound somewhat.   Lift seems to have plenty of power.  (I did not install the assist spring on the flag.)

I’m wondering if there is air in the hydraulic lift lines?   Is there an air bleed screw I was supposed to have bled?

The transmission, forward and reverse works great and does not create the whine! ( well maybe for an instant when first engaged)

Any Ideas?

[Darb1964 1,014]

Is the fluid level in the safe range on the dip stick? Sounds like it's low.

[wallfish 15,926]

Operating the hydraulic circuit will get the air out of it. The oil pushes through everything, hoses, valve, cylinder taking the air with it back to the reservoir (Trans case) where the air is then released as it bubbles out of the oil. 

[kpinnc 10,736]

Your coaxial charge pump is somewhat similar to the hydrostatic motor. When you load the hydro by climbing a hill or pulling a load, it whines quite a bit. The charge pump is gonna do the same thing when you lift something like a snowblower. 

 

My 520-H hydraulic lift has a little squeak when I lift the mower deck. The hydro was serviced earlier in the year. It made no difference. 

 

Another thing to consider- the spool valve Wheel Horse used has no relief circuit. Point being, any position between fully open or fully closed is restrictive on the hydro charge pump. That makes it squeal too. 

[Handy Don 10,609]

6 hours ago, kpinnc said:

the spool valve Wheel Horse used has no relief circuit.

The spool valves used with the Eaton 1100 do have a 700 psi pressure relief built in. When you stall or max out the lift in either direction, you’ll hear it squeal as the oil is being bypassed through the spring-loaded valve. Overloading the charge pump will damage its internal seals--it has no intrinsic bypass capability--and stalling the flow would mean starving the “makeup” supply of oil to the intake for the motion pump/motor--not good.

The Sunstrands have pressure relief built into their pump body (when the proper cone and spring are inserted in the proper port) so their valves didn’t need separate pressure relief.

Edited November 20, 2023 by Handy Don

[kpinnc 10,736]

1 hour ago, Handy Don said:

The spool valves used with the Eaton 1100 do have a 700 psi pressure relief built in.

 

I mean they are either closed or open fully. I used a completely wrong term. Sorry about that.

[Gary S Minnesota 51]

Thanks everyone for your responses.  

I can’t believe didn’t think to check the oil level.  That will be the first thing I do tomorrow.   I do recall pouring in additional oil immediately after I drove and cycled the lift a few times following the oil / filter change last summer.  The dip stick reading appeared to be good at that time.  No leaks that I have noticed.

At any rate, it appears the “whine” i noticed is not too unusual.  

I’ll make sure the oil level is proper and then cycle the lift a few times to work any air out of the system!

 

[Handy Don 10,609]

23 hours ago, kpinnc said:

 

I mean they are either closed or open fully. I used a completely wrong term. Sorry about that.

For sure. Trying to feather one of these valves is a real exercise in frustration 😉