Cylinder rebuild

[Acoals]

Cat 315C L, CJC2798

A question or two about rebuilding the boom cylinders. I am familiar with working on the smaller cylinders on skid loaders and mini excavators and such, but I haven't done cylinders as large as these. What are the torques like on the big nut inside? I don't have a torque multiplier or big torque wrench. I have 3/4 drive tools and such. Should I take a crack at it or just take them off and take them to a hydraulic shop?

 

[Junkyard]

The torque values on them can be pretty high but often a little heat and leverage you can break them loose. If the shop is nearby it might be worth letting them do that. I rarely pull the barrels off the machine, I leave them pinned in place and just pull the rod and gland out. You’ll need some support for them as they’ll end up horizontal once you remove the boom pin. If you see that the barrels need honed you can proceed to remove them after you have the rods out.

If you have a good way to hold the rods to break the nuts loose you can build a wrench and use another machine or a chain hoist to apply the torque.

 

[Acoals]

I am more worried about tightening them back on. Do you just stuff it on as tight as you can and let the locknut hold things together? I can put a pipe on the 3' handle of the 3/4 ratchet, but there are limits to that.

 

[Junkyard]

If you can break it loose then anything you can apply to tighten will be sufficient. Some red thread locker wont hurt either. It’s not an exact science torquing them back down.

 

[Nige]

If it's only a re-seal and all the hard parts are going to be re-used you could mark the nut and the end of the rod with a centre punch and simply re-tighten the nut so that it comes back to the same position as it was before you removed it.

Tightening spec for the nut is 3319 ± 170 lb ft. You are not going to get anywhere near that with a 3/4" ratchet however long a pipe you put on the end of it, at least not IMHO.......
I think you need to investigate the hydraulic shop option.

 

[Delmer]

Plenty of wood blocking to keep everything supported and safe. You don't want to get it back together and find you pinched a seal going back together and have to do it all over again. A 3/4 drive is probably not big enough, you can make a box end wrench out of plate, or have one cut with a plasma or water jet, might get lucky and find a slug wrench on ebay etc. or a junk socket and weld it to a plate then a pipe to the plate for your 10' lever.

 

[Nige]

If you're going to look around for a wrench, the hex size on the locknut is 85mm. The thread on the cylinder rod is M56 x 2mm pitch.

This photo might give you some ideas...... I'm not sure how big the nut was on that particular cylinder but probably larger than 85mm.