988H Cat lift cylinders and mounting seals S/N BXY00384

[kshansen]

Looks like I have to pull both the lift cylinders off this 988H due to seals leaking at the mounting pins, not the rod seals. Figures one seal on each cylinder is leaking!

This machine has what Cat calls "Maintenance Free Linkage Seals"

Looks to be a pretty simple job, IF they will come off with fenders and front tires in place. Looks close.

Just wondering if there are any "got ya's" Looking at the book/SIS seems I need a couple special tools to install the seals. Or is it doable with out them if one is very gentile with them like the Duo-cone seals?

One possible advantage is bucket is off being rebuilt so if I need to hold boom up to gain clearance a couple good Jack Stands should take care of that.

 

[Nige]

Ken, Sorry I missed this due to my move back home. If it's anything like a late-model 992 be prepared to replace everything in the joint. The fact that the seals are leaking usually means there is wear in the joint somewhere. The MFL seals will go in by hand despite what the manual says, just like a Duo-Cone all it needs is a bit of care to get the seal in square if you don't have the recommended installation tooling. I would think you will most likely have to replace the bearings in the cylinder and the rod as wear in those bearings is probably what's causing your oil leak. The worn bearings will come out easily with a run of weld round them, the new ones go in a treat with liquid nitrogen.

 

[kshansen]

Well when I pulled the cylinders it was somewhat obvious why some of them had started leaking. The rubber rings that act as the springs to hold the seals in contact with the steel parts out of ten total seals on this machine five of them were twisted when installed a couple years ago. The cylinders at that time were removed, resealed and installed by the local Cat dealer. As you say they go in easy with a little care. Actually much easier than the Duo-Cones! After installing these with out the "Special Tools" I think the tool would actually be more of a hassel!

Bearings and shafts looked just about new so at this time only replaced the soft parts.

Now just need to finish replacing some dried out orings on the steering pump and transfer-case bearing retainers and this machine should stop marking it's place like a Harley!

Have used that weld to shrink bearings a few times guys are always surprised how easy it makes things come apart!

Would be nice if we could get a few days when the overnight temps stay on the plus side of the F scale on thermometer, at least the shop is fairly warm!

 

[Nige]

..... at least the shop is fairly warm!

Sitting at home it's even warmer ..........

 

[kshansen]

Well the end of April I will be doing that Myself!

 

[Nige]

I forgot to mention that it's easy to get one half of the MFL seal (the inside half) in the joint upside down. If that happens it will all fit together but you will not get the correct amount of pressure on the sealing face and the joint will leak as a result. IIRC it was a process of trial and error for us because it was not intuitive what was supposed to be the correct orientation of the load ring.

 

[old-iron-habit]

Well the end of April I will be doing that Myself!

With the exception of about 10 hours a week "mentoring" the youngsters, I have been doing that since January 20th. Should have done it a couple of years ago.

 

[kshansen]

Yesterday boss asked me if he had an emergency if it would be ok for him to call me for ideas, not to work. I said yes don't dare tell my wife

Will be interesting to see how things are a year or so down the road, just wish someone a bit higher up could understand the need for having a replacement around for a time just to know where and what spare parts may be on hand. This will be at least the third quarry in the state for this company that has had the only onsite mechanic leave in the last couple years.

Many things are easy to pick up on by a new person. But things like not knowing how to by-pass the Pre-lube system on a Cat loader or haul truck could cause a machine to be out of production for maybe a day or two if they need to call in an outside contractor mechanic. If you know right what to do it could be back to work in less time than it takes to type this sentence!

I'm sure many here have things they do without giving a moment thought just because you have seen the problem many times over the last few decades.