Cat cylinder reseal?

[Welder Dave]

I need to do the bucket cylinders on my 931B. I'm going to cut an octagon wrench out of steel to get the gland nut off and was hoping I can just take the rods in to get the new seals installed. The cylinders rods look like new but started weeping out the end too much . I don't think I need the barrel honed and I can polish the cylinder rods if they need it. Is it common to have a hyd. shop just change the seals on a machine that doesn't get a lot of use? One place suggested it could cost $400-$900 per cylinder to rebuild if I took the complete cylinders in. That seems like a lot money for cylinders that started weeping after 30 years. I think the cylinders use a bolt to hold the piston rather than a nut and I don't know if they have Loctite on them but are really tight. That's why I was thinking of having a hyd. shop do it with the proper tools. Was also wondering if I take the cylinders apart if the cylinder barrels will rust being open in cold weather for about a week. I have the machine in a non heated shop. Would it be better to wait till spring? Just looking for opinions. I've done seals in my skid steer with no problems but these are little heavier duty cylinders.

 

[Cmark]

Yes, it's not unusual to take just the rod assembly to a hydraulic place and have them replace the seals. However if you've got the wherewithal to get the rod out, it shouldn't be outside your capabilities to fabricobble another hex wrench and complete the job yourself. The cylinder is only 4" which really isn't the mother-of-all-cylinders. You just need to anchor the end and supply enough force to the bolt.

If you're worried about rust, soak a rag in WD40 or similar, shove it up the bore and seal it with a plastic bag.

 

[kshansen]

Cmark is on the mark here as always. Dave if you are able to fab a tool to get the gland nut off you probably can do the same for the piston bolt.

Not familiar with the 931B but often machines have a hitch pin that works to hold the ram while removing the piston bolt. Pin the ram in the hitch and maybe support the other end with a jack stand and use a pipe on a breaker bar to loosen the bolt. If they are factory assembled I would not expect Loctite but that is a possibility.

I just took a look at the the tilt and boom cylinders of a 25Y 931B and the bolts that hold the piston on are spec'd to have anti-seize on the threads and be tightened to "only" 800 ft./lbs. That works out to 160 pounds of force on a 5 foot breaker bar. I say give it a try!

 

[DMiller]

Is not that hard to install a freshly packed piston, easiest to use shim stock and hose clamps like a ring compressor/piston stuffer.

 

[mitch504]

I usually use a regular piston ring compressor

 

[DMiller]

I find it easier to get it off the cylinder ram than with a compressor, dependent on the end fixture.

 

[HTRN]

FYI, if your able to, leave the cylinder attached to the machine and loosen the gland head first, then remove it. Sometimes its alot easier than trying to hold it in a vice or something... you can also do the same after you take the rod out, just run the pin back through the rod end and then loosen the piston nut. * just did this today on a 980M loader steering cylinder*

 

[Welder Dave]

Thanks for the advice! I believe my serial number (25Y1916) uses 3 1/4" bucket cylinders. I plan to leave the cylinders connected to loosen the gland nuts. I like the tip about WD40 and a rag. I was thinking of spraying WD40 in the bore but soaking a rag makes sense. I have a tractor or skid steer I can apply force with on a snipe if needed. I think pulling the complete cylinders is more of a pain and not really necessary. I'm not sure what all comes in the seal kit just don't want to bugger up any seals. I can make a mark for how tight the gland nut and rod nut are. I guess it would be worth trying and then I could fix a stabilizer that creeps and a 4 in 1 cylinder that weeps. Do you need to compress the seals to get the piston back in the bore? On my skid steer they just slid in. Should I use Loctite or just anti-seize on the rod bolt?

 

[Cmark]

As far as removing the whole cylinder goes, it depends on what level of repair you want. In my book, a cylinder overhaul involves measuring/honing the barrel and polishing the rod as well as seal replacement. However I totally get that owners of older machines don't want the additional expense and trouble, and that's fine. It's just one of my pet peeves that some hydraulic shops will claim to have "overhauled" a cylinder when in reality all that they have done is thrown in a set of seals. Anyway, back on topic;

Piston seal replacement is a bit of a crapshoot. Sometimes they go on easy and the piston will enter the cylinder with a few bumps with a hammer. Other times they can be hard work. Heating them up in hot water can help but you can then end up with them too big and difficult to go in to the cylinder.

Worst case scenario is that you have to wrap a piece of steel pallet strapping and a hose clamp around it and leave it for a couple of hours. Not such a big deal if you're not under pressure of time and it's your own machine.

Lube or loctite? I say always follow the official D&A instructions. In this case, lube.

 

[Delmer]

You can see the rods before you take them apart so you know if there's any bad scratches there or if they're bent. If the seals died of old age, I'm less concerned about the condition of the inside of the cylinder. Moisture is what makes rust, not cold. If it's going to get damp while they're open, stuff dry rags or paper into the end and tape up the end with plastic and duct tape, or aluminum foil tape.

 

[kshansen]

One point that some don't seem to appreciate is the importance of cleaning the work area before stating the job. I understand that not everyone has a good pressure washer and a nice heated shop to work in but a little cleaning before disassembly can save time and possible problems down the road.

And as discussed keeping the opened parts clean while working on the piston/rod assembly is very important. Just something as simple as slipping a plastic bag over the open cylinder and holding it in place with a rubber band or oring will do wonders.

Not sure on this particular machine but something to keep in mind when working on a machine that you don't know the full history of is that some Cat cylinders have over-sized seal kits available for repairs. Making it a good practice to measure the bore just to assure yourself the one you are working on is "standard".

And don't be too surprised if the new seals look different from what you remove as Cat has made a few changes in the style of seals over the last several decades!

 

[Welder Dave]

According to the hour meter the machine has about 5600 hours which I think may be close judging by the overall condition of it. Undercarriage had been done before and I've put 1000 hours or so on the undercarriage I put on. Seals were weeping a little out the rod end around freezing temp. but a week and a half ago around the same temp started leaking worse where they are making a mess on the boom. They would weep a bit just sitting too but when I had the boom up to fix the wiring, the bucket hadn't creeped down at all after 2 days. After a week it creeped down some. No sense taking the cylinders apart and just doing the rod seals.

 

[mitch504]

The steel strapping and the shim stock are both great ideas. That's what I love about HEF, you can do something the same way for 30 years, and then learn a new idea.

 

[kshansen]

The steel strapping and the shim stock are both great ideas. That's what I love about HEF, you can do something the same way for 30 years, and then learn a new idea.

Just a word of caution if using any thing like this to compress the seals to smooth off rough edges so as to NOT cut the seals!

 

[Welder Dave]

I spent some time cutting and fitting a 1/2" plate to fit the the gland nut but it didn't work out. I could have cut another one out of heavier plate but it's a little cold and I didn't want to waste more time not knowing if it would work or not. The cylinders are on top of the boom and easy to remove so just going to take them in. If it was summer and I had a little more time and daylight I might have tried making another tool. A tool cut out of plate to fit the gland nut has to be a perfectly tight fit everywhere on the gland nut. Cat has rounded corners on the gland nut which doesn't help. Maybe a big pipe wrench would work but I don't have one and just need to get the cylinders fixed. When you don't have a perfect set up shop and all the proper tools sometimes it can be more frustrating than anything else, especially when you have no help. Hopefully I can get them done for about $300 a cylinder.

Does anyone know how many shims are on the bucket cylinders on the loader tower. I pulled one cylinder and saw a shim fall but found it. I think I might have heard another shim fall but not sure because I couldn't see it. I'm wondering if there's supposed to be a shim on each side or if it's not super important.

 

[wosama931b]

Hi Dave , I used a 4ft. pipe wrench , and a lot of wd40 on the thread , broke one chain wrench , and found a new chain wrench that worked out . ,l used a come along to pull out the shaft , and it was not to hard to fix, but keep it clean as possible

 

[Welder Dave]

I'm not sure I know anyone with a 4' pipe wrench. In the summer I might have played with it some more. It's going to be over $600 to do both cylinders but I don't know how much more yet. I don't have a lot of time to work on it so just said $#%@! it and took them in. Decided on a shop to take them to and was a little miffed that he said they use pipe wrenches on the tough ones. I would have thought an established hyd. shop would have some special tooling to get the gland nuts off.

 

[wosama931b]

Hi Dave , I know that you mean about the gland nut , and I was reluctant to put the large pipe wrench on. I spent a lot on tools to work on repairs , some times it's best left to the pros.

 

[Welder Dave]

Apparently the chrome isn't in good shape and the cylinders have a .0010" bend which they said could take out rod seals. Also said it's common for loader bucket cylinders to get bent. 10 thou bend over 2-2 1/2' doesn't seem like very much but I don't know what the tolerance is. They can straighten and re-chrome them and will hone the barrels as well. Complete repair for both is about $820.00.

 

[Delmer]

I suppose that's better than paying $600 for just new seals, huh? not bad at all.