Need Blackhawk S4 help, please.

[olddog1]

I just finished overhauling the hydraulics in my S4 floor jack. I used all new packing and check balls throughout. The jack raises and lowers fine and will stay raised as far as it's lifted, but it still won't lift anything beyond a 12-pack. When it raises to the load it feels like it's just bypassing internally. The release valve seems to be seating properly and I've bled it to the point where there are no more bubbles. I guess it's an internal leak of some sort and I'm wondering if it has to do with one of the check valves? Has anyone had a similar issue and can offer any suggestions? Thanks in advance!

 

[paulsomlo]

If you raise it then stand on it with the release valve closed, does it stay up?

 

[olddog1]

I didn't try that. I'll do it tomorrow and let you know how it goes. Thanks for the help!

 

[olddog1]

I can set 150 lbs. on it after lifting it half way and it stays put.

 

[paulsomlo]

OK, you can eliminate the release valve then. Time to look at the check balls, then the seals.

 

[olddog1]

I'm thinking (hoping) check balls. The seals are all new and went together as you'd expect them to have. Maybe there's some crud or rust/corrosion on a ball seat somewhere. I appreciate your help with this.