Loader "Leak" or Loader "Fall"

[btb]

Loader \"Leak\" or Loader \"Fall\"

I know this has been covered before, but I couldn't find any older posts using the search feature. Why do loaders "fall" or "leak air" back to the ground if left in the air with the engine off? I don't seem to be leaking oil, but the loader slowly falls back to earth, while the MMM or ballast box stay upright for weeks. Mainly just curious (it's a little annoying though).

Thanks again!

Brian

 

[kennyd]

Re: Loader \"Leak\" or Loader \"Fall\"

Brian,
The leakage is due to the DSCV(Dual Selective Control Valve), the spools that move back and forth to direct the oil flow are a machined fit into the block, there are no O-rings or seals, so there is some bleed off. This type of valve is much cheaper.
The valves used on large construction equipment, man-lifts, cranes, etc. use a Poppet Valve or Pilot operated check valves to control the cylinders, there is no leakage with these, but they are allot more expensive. That is why you see cranes sitting for days with the boom up and it never moves.

Clear as mud?

As for your search, be sure to change the date range to "ALL POSTS", as it defaults to only one week.

 

[dieselmotorhead]

Re: Loader \"Leak\" or Loader \"Fall\"

That is why I was waiting for CCM to get the side link cylinder( top-n-tilt ), they set it up with the pilot operated valve=no leakdown. Spool valves have inherent leakage, but with skill give "feather" like control, and in use you would never notice the leakdown on good valves. Just when you are parked. As mentioned above about expense --the cost of valve bodies on some excavators would buy you a solid CUT.

 

[btb]

Re: Loader \"Leak\" or Loader \"Fall\"

I appreciate the input, and I was sure there was a valid reason for the fall. Makes sense why "real" backhoes, excavators, and the like can be displayed for weeks with the loader/boom in the raised position.

Thanks again fellas!

Brian