1. Thank you for visiting HeavyEquipmentForums.com! Our objective is to provide industry professionals a place to gather to exchange questions, answers and ideas. We welcome you to register using the "Register" icon at the top of the page. We'd appreciate any help you can offer in spreading the word of our new site. The more members that join, the bigger resource for all to enjoy. Thank you!
  2. ALL NEW MEMBERS READ THIS FIRST!! Thank you for joining Heavy Equipment Forums! If you are new to forums we communicate with "Threads", please search our threads to see if your topic may have already been answered and if not then click "Post New Thread" in the appropriate forum. This will allow all of our members to see your question and give you the best chance to be answered. After you've made a number of posts you will graduate to Full Member status where you'll see a few more privileges. Following these guidelines will help make this the best resource for heavy equipment on the net. Thanks for joining us and I hope you enjoy your stay!!

cat 236 - i just rebuilt lift cylinders, but lift arms keeps leaking down

Discussion in 'Skid Steers' started by makesumwake, Dec 31, 2020.

  1. 92U 3406

    92U 3406 Senior Member

    Joined:
    Jan 3, 2017
    Messages:
    1,729
    Location:
    North of there but east of here
    The thing with standard hydraulic cylinders is if the piston seals are gone, they will only drift out, not in.
     
  2. lantraxco

    lantraxco Senior Member

    Joined:
    Jan 1, 2009
    Messages:
    7,698
    Location:
    Elsewhen
    Depends on the rest of the system and the load imposed. When they go into displacement mode, with only the area of the rod to hold the load, pressures can shoot up increasing the typically minor leakage in the valves, or in some cases opening the port reliefs.
     
  3. 92U 3406

    92U 3406 Senior Member

    Joined:
    Jan 3, 2017
    Messages:
    1,729
    Location:
    North of there but east of here
    Definitely. I meant just a sole, isolated cylinder should not drift inwards.
     
    Jonas302 likes this.
  4. makesumwake

    makesumwake Member

    Joined:
    Dec 13, 2015
    Messages:
    12
    Location:
    miami, fl
    I took apart the lift cylinders again to take measurements with calipers and bore gauge.

    piston rod shaft diameter = 40mm (39.96mm)
    piston head seal diameter = 60.55mm (largest diameter seal on the piston head)
    piston head wear rings = 59.90mm
    cylinder bore = 60mm + 1/1000inch

    there isn't much force required to pull the piston out of the bore.
    I can pull the piston out with one hand, and push it back into the cylinder with one hand (50lbs of force required maybe)
    These clearances are probably too loose, and is making the lift cylinder operate in displacement mode?
     
  5. Welder Dave

    Welder Dave Senior Member

    Joined:
    Oct 12, 2014
    Messages:
    6,570
    Location:
    Canada
    It doesn't seem like the seals are the problem in my opinion.
     
  6. heymccall

    heymccall Senior Member

    Joined:
    Feb 20, 2007
    Messages:
    3,349
    Location:
    White Oak, Pa
    Was the boom lowering valve checked?
    Were the boom UP and Down relief cartridges swapped?
     
    mg2361 and Nige like this.
  7. Vetech63

    Vetech63 Senior Member

    Joined:
    Aug 10, 2016
    Messages:
    4,045
    Location:
    Oklahoma
    I'm lurkingo_O
     
    Nige and mg2361 like this.
  8. LEGO

    LEGO Active Member

    Joined:
    Feb 13, 2021
    Messages:
    30
    Occupation:
    Diesel tech
    Location:
    Texas
    This would work if the lift cylinders dropped without any weight on the bucket, and it seems its only dropping with a load. but yes it would work, I know cause I did this with a backhoe, but the lift cylinders where dropping without a load, turns out when capped the boom did not drop. spent more time troubleshooting and turns out the spool in the lift valve was damaged with a big deep scratch.
    I guess in this situation if the same was applied, but with a load on the bucket youll get a good test to verify if it is in fact the cylinders or not. I havent seen the machine but I dont think it is the cylinders. Its something else.