Well, my hydraulic thumb cylinder is finally leaking way too much fluid to ignore any longer. After opening it up with insane difficulty, I was shocked to find the seals were totally stuffed, and there was a lot of metal to metal deep scoring on the end cap near where the outer seals attach. It is my first peek inside a hydraulic cylinder so I was puzzled as to what caused such damage. Even two hydraulic 'experts' said I must have ingested metal through the wiper seal or though bad oil. Well this didn't make any sense to me as 95% of the cylinder bore looked perfectly smooth. So what caused such damage? So I pay close attention and there it is staring right in front of me. Can anyone else spot the problem here ?
I'm no expert so have no rep to damage... The thumb hitting the cylinder ?
Nice guess, but no. Take a look at the marks on the piston seals and think, 'how the **** does that happen? Then look at picture 3.
I see... Did you use a pipe wrench on the piston ? The marks on the piston threw me off the excess threading on the cylinder.
You got it. Yes I used stillsons in the safe side of piston head. The marks look similar to the marks on the damaged piston seals but the wrench was not used on the piston seals. Yep, it seems the Chinese made about 3/4 inch of excesss thread into the cylinder bore, and just jammed the piston and seals over the thread basically ensuring that they were fucked from day 1. Now I have to try and hone away this thread to get new seals in. I hope this is possible.
While you'll be able to smooth away the threads, the piston seal won't work in that area for very long. You may consider a spacer to prevent the piston from traveling over the excess threaded area. Sort of like a retract stop but internal to the cylinder. Your thumb cylinder will lose only 3/4 inch of travel when extended.
Ok great idea thanks, but I probably still need to take a few thou off that thread to avoid scoring the seals when installing piston. All in all, I got 4years out of it, and for $1500 shipped to my door, I'm still a happy man. But geez, those Chinese are shonky.
What would it cost to replace the cylinder? It may be a more reliable fix than removing that excess thread. Cam
Thats a a hard one because the oring on the gland seals where the excess thread is cut so will always chop the oring. If you clean the thread the oring prob will not seal anyway unless you filled thread with plastic steel or bronze weld and hone
Guess you could try loctite thread sealer on the gland thread and coat o ring with something whilst assembling
Yes I had the scored thread area shimmed smooth. Got a slightly larger Oring to accomodate and bought a bunch of loctite thread sealer. Greased the seals with Vaseline, fingers crossed.
SHE will be right thats what i would of done