LX865 servo pump shaft seal.

[tech.35058]

Todays project is to stop the hydraulic oil from transferring into the servo pump drive gear case, and improve any thing else we see along the way.
I tilted the cab, got the pumps out, cleaned up the hole, scraped 2 or 3 gallons of crud out of the floor under the pumps, wiped down some with solvent, spray painted the places where the paint was missing, looked at the hoses (EEEK!), cleaned up the pumps, and starting with the left pump(with the charge pump on it).
I got the drive gear off the shaft, removed snaprings, poked a hole in the (new style) seal, threaded a screw in it & removed seal with a slide hammer. inspected the shaft, no seal wear groove , cleaned out the seal bore cavity, all looks good, lubed shaft, lubed new seal lips & outer rim( with 30 wt motor oil, 1st cousin to specified hyd fluid), attempted to re -assemble. As expected, the rubber coated seal did _not_ want to go in the bore. (My first experience with this style seal was several years ago, working for some one else, so they got to pay for my educational experiences. I have damaged a few seals before getting here. ) I re-lubed the outer part of the seal with STP, found a big deepwell socket that would clear the shaft & apply even pressure around the seal,& carefully _forced _ the seal into the bore, re-installed the retaining snap ring & seated it in its groove with a small punch & hammer. This evened out the seal in the bore, as the snapring forced the seal a little deeper into its bore as I tapped the snapring into its groove. All of this was about what I expected.
On the right hand pump, I got to the part where I punched a hole in the seal to remove it, the old seal nrotatednin the bore as I tried to poke a hole into it. as I attempted to screw the slide hammmer screw int my hole, the seal popped out of the bore (_way _ too easy! )
So, I checked the parts list, seal is described as 2 inch O.D.
I mic'd my new rubber coated seal, ( how accurate is this going to be?) found it to be 2.0041 inch dia.
I used divider style calipers ( mic'd across the calipers) to measure the seal bore.
outside of the snap ring groove, the bore size is around 2.0105 to 2.0164. Like I said, how accurate is this?
inboard of the retaining ring groove, the seal bore appears to be 2.0005
So this appears to be about a 0.0035 or so interference fit. does this sound about right?
I also mic'd the old seals as best I could, the "normal" one (I know its distorted ) was 2.0015,
the other was 1.9974 x 2.0012, pretty distorted & mic'ing over the rubber coating.
The seal bore & the new seal sounds about right(?), but I had never measured these before, previously ( in my "professional engine tech" days ) I just put them in, no issues ever, after I started lubing them to get them in the seal carrier bore.
I do not want this leak to continue, do not want to have to pull all this back apart, so I am asking, has any one had this experience?
Is there anything I can do to "enhance" the seal housing to seal bore seal ?
I am considering a little "hydraulic sealant" on the bottom of the seal bore.
( I would say RTV would be a serious no-no here)
( the service manual specifies hydraulic sealnt on 37degree sealing faces of the hose fittings, so I should get some any way)
but maybe a tiny bead around the edge under the retaining snapring?
or maybe dribbling a tiny bit of something that would cause the rubber coating to swell around the outer edge?
( then wipe off the excess, but what stuff to use? super glue? (cyano-acrylic?)
Any one have experiences, trials or errors to share ?
Thanks, CE

 

[Shanmar]

I have no specific knowledge but I don't think 3-1/2 thousandths interference sounds too bad.
Some other thoughts:
- I had an LX885 that bolts that hold the pumps to the housing repeatedly loosened. So, I'd suggest using at least blue loctite on them.
- I had issues with the o-rings under the elbows for the main high pressure hoses leaking. If they haven't been replaced, I'd seriously consider it while you have good access.

 

[tech.35058]

I have reassembled my machine. I have not "completed the repair" because it appears that I am still transferring oil into the gear case.
When I do it again, it should go much better, since I am now "experienced". ( & I have made a cab jack, & all the crowfoot wrenches needed for the job)
I failed to heed Shanmar's very good advice to replace the o-rings while I had the pumps out. After all, mine weren't leaking. After all the gyrations, removing hoses, replacing hose, tightening hoses, they were now leaking. And Tedious to fix in the machine.
For the un-initiated, JIC caps & plugs in the -16, -14&or-12, -8 and maybe -10 will be useful if you do not totally drain your oil tank.
I already had a set of smaller crowfoot wrenches, but this job called for 1&1/2 inch, 1&1/4, i think 1& 1/8, and 7/8. I could have used a 9/16, also, but just didn't. It is not impossible to make your own, but it takes a lot of time.
I am of the opinion that torque specs are published for a reason, & have over tightened & under tightened enough stuff to do me. Since I had the spec, and a torque wrench, I took the time to use it.
( My former employer would have been unhappy if I took time to do this on his job, but this is my machine, and any do-over is on me.)
I will recheck for oil transfer since I ran the machine several hours yesterday, but I expect this to be a "do-over". when I installed the new rubber cased seals, one would not stay in the seal bore, but kept "popping out". I pressed it in & installed the retaining snap ring, but this is my prime suspect.
in the do over, I will attempt to get the proper old style metal cased seal. we shall see.
I will try to post photos of the torque charts later, for any one that would like to kknow the "real specification"
Remember, if you replace a grade 5 bolt with a grade 8 bolt, the female threads( unless you changed them) are still made for grade 5.

 

[Shanmar]

Cab jack? That's cheating. You won't use nearly enough 4 letter words with one of them.

The popping out seal does sound suspicious. I had a similar problem on an L185 which is a different arrangement, but still a pump with a seal. In my redo we replaced the pump shaft as well thinking that the small wear groove under the seal may have been the problem. I didn't leak afterwards, but I'm not confident it was the problem, but I had a shaft with fewer hours on it so made sense to make the change. Just passing it along.

How many hours on it?

 

[tech.35058]

OK , here are the torque specs, just in case any one is interested.

 

[tech.35058]

Follow up ... It turns out , the oil level in the drive gear case is stable, so that issue is corrected.
Unfortunately, when I replaced the o-rings on the fitting mounting bosses, I used o-rings from a "(universal-general purpose-fit'em all)" kit. These o-rings failed under heat & pressure so I was losing oil there.
The parts manual describes these as "duro 90" o-rings, special, stronger, harder composition. I finally found an auto parts store that knew what a STOR boss was & had correct o-rings. An Ebay search for "Gates -o-rings" found a small kit so I will have correct generic parts for next time.