View Full Version : Wanted: Hydraulics Guru

06-06-2008, 10:59 PM
Have a l940's ex. military clark forklift. Found water in hydraulic fluid and suspected lift cylinder seal as cause. So got a new seal and set of 4 v-packing(4" o.d.-3 1/8"i.d.)based on old v-packing from piston head(old packing was leather--new packing-unsure of material composition). PROBLEM: Unable to get piston head with new packing into lift cylinder even with use of piston ring compressor,hydraulic fluid, and prior prep of cylinder with wire brushing and cleaning. Measured lift cylinder i.d. as 4.0". Catalog shows next smaller v-packing as 3 7/8"o.d.- 3 1/8"i.d. Any ideas? Thanks Paul

Tim Clarke
06-06-2008, 11:27 PM
Well, lemme see. The way I read your post, I think you're saying the v packing goes on the piston, which slides up an down the cyl tube, No? All the old stuff I've fooled with would have either cast Iron piston rings or, a cup [leather or otherwise] on the end of the rod. The V packing [also called chevron packing] would go in the end of the cyl tube, around the rod. And then a scraper or wiper to keep the bad stuff out. There would then be a nut to compress the V packing, to tighten it into the cyl tube and around the rod.

If you have V packing on the piston, it's time to do a little machine work on the piston. Regroove it to take the more common polypack type seal. these are a lot easier to deal with on assy. Check out the poly seals wherever you got your new V packing, they'll be able to help you with engineering data for groove sizes, etc.

Hope this helps, TC

06-06-2008, 11:36 PM
Water comes from the tank, any cylinder made worth a crap will never get a drop of water in it.

Iv made lots of big multi stage cylinders and water was never an issue, no way in hell.

I have seen shop where the boss was a cheap punk and used water in his 350 ton pressbreak.

Water getting into a sealed system? No way in hell....

06-06-2008, 11:37 PM
Another vote for poly pack seals.

06-06-2008, 11:39 PM
Another vote for poly pack seals.

I like them too, no way in hell would one drop of water get in...

06-07-2008, 09:38 PM
Thanks for your responses. The rod seal is a common lip type of seal held in the cylinder cap. The v-packing is on the end of the piston with the open end of the "v" facing the bottom of the cylinder. This is the first part to enter the cylinder and I can't get it in. It is held in place by a v-shaped ring that fits in the v-shaped groove in the packing and is held in place by 4 bolts that are safety wired together. When I took the old packs out the 4 bolts were in tight. Does the amount of pressure exerted by the retaining bolts expand the v-packs for a custom fit? I don't have a manual specific for this model of yardlift and its not discussed in what I have. Paul

06-07-2008, 10:12 PM
The bolt tightness will only effect the sealing if the seals bulge before the retainer bottoms out on the piston.Most times pressure does the sealing.

You might try making a tapered ID sleeve and use it to install the piston.

Tim Clarke
06-07-2008, 11:57 PM
Time for a photo, so we all can see exactly what you're dealing with.

Regards, TC

06-08-2008, 02:53 PM
If you can start the piston into the cylender witht eh bolts loose and then tighten them once the piston is inside the cylender that is the way to go. Because of the 2 special rings at teach ent of the seal stack the seal gets expanded (OD grows and ID shrinks) and that gives the piston its initial seal. after it is used a while it will not be so tight but will seal just fine. Maybe some sort of tapered sleeve was the way the did it in the factory - but it would need to be a several inch long taper and polished. a bit of a pain for just 1 cylender.