I lost my first hydraulic seal the other day on a job. I took it to the only rebuilder in town to fix it and he said he would have it back in two days. Five days and five hundred dolllars later I get it back and finish the job. The customer was on a close time schedule and was just about to tell me to get my gear off of his land so he could get someone else to finish the job. When I got the invoice the seal kit was only 70 dollars and it was 430 in labor. Do any of you guys repair your own cylinder seals? What is involved with rebuilding them? I have done a few smaller ones that I could just work a rope seal into but I havent ever taken on a full size excavator cylinder. I was thinking about going ahead and ordering seal kits for all of the cylinders and keeping them on hand so it wont cause me any down time when they blow out.
If you are working on full sised machines be prepared for some realy high torque specs. I thing the the piston retaining nut on a 320 cat stick cylinder is like 12000ft/lbs most shops have a cylinder table that is made for these applications.
i agree a komatsu 300 main boom torque is around 20,000. but try a good service mechanic with a truck. thats what we do. buy the seals and when one goes make a telephone call. our guy comes out and remove the cylinder and at night if nessesary repair and replace by the next morning.
WOW didnt realize the specs were that high. I guess I wont be rebuilding these things myself then. Waiting for the seals took most of the wait time so I guess I will just keep them on hand and take them to the shop.
Stick cylinders are what are real high. Generally they run in the 7,000 to 12,000 foot pounds of torque range on the machines I've worked on. Boom cylinders I've worked on generally were around the 5,000 foot pound range as were the buckets. I've never worked on a cylinder that took twenty thousand foot pounds but I suppose if the machine were big enough it would probably need it. There are no short cuts either. I have been on several jobs where the nuts weren't pulled tight and they ended up pulling the threads off the rod and sending 10,000 little knives through the hydraulic systems.
As was pretty much said before the smaller cylinders are easy. The caps can be pulled off with a hammer and chisel or a spanner wrench and the nut can usually be removed and installed with a 1" impact but should be torqued on install. The large cylinders such as most boom or lift cylinders should be done by a pro, mostly due to them having around a 4" nut and high torque specs. Some machines are easier, alot of the Komatsu stuff I work on has two half clamps with four bolts retaining them and the piston, they are simple to use. As for the seal part as long as you understand how a lip seal works and to lube your seals and o rings its pretty simple.