Hey folks, I just recently purchased a Komatsu PC-78MR for myself and my dad to use around the property. I think it's a 2008(can't remember at the moment) and had 2037hrs on it when I walked it off the stepdeck it was delivered on. Other than offloading it and walking it over to the shop, it's not had anything done with it as we have other projects needing attention. While messing about with it in the yard, we both noticed that on swing, there is a noticeable rumble in the seat. He noted that the dipstick showed low on the and he suspected the circle hadn't been greased in a while. He swung it around slowly while I sat on the machine and gave it a good dose of grease. Topping up the oil and a good grease job didn't seem to change the feel from the seat. While I was sitting on the machine pumping grease, I didn't feel a thing at all. Past experience tells us that the swing should be smooth but since neither of us have ever been on a Komatsu, we wondered if maybe it has a design or configuration that is just a little bumpy. it doesn't jerk or hesitate and is smooth other than the rumble in the seat. It shows the same feeling throughout the swing and it doesn't have any areas or sections where the feel or "tone" of the rumbling changes at all. Something tells me we may have possible damage but can't be sure just yet.
You should probably get an operation and maintenance manual for the machine. As I recall that machine is a zero tail swing unit. I don't know if the machine has a gear box swing reducer or is just a swing motor. You can get a lot of noise and vibration out of any machine at times.
Good day Assuming that the low oil refers to the swing transmission I would suggest immediate investigation (Lube oil in the slew pan), use of the swing with failing bearings could be expensive, the noise you describe could be loose transmission fastenings so please make a check of movement. Kind regards Uffex
Machine came with original factory manual. I didn't have a lot of time to look it over but I didn't find much in the way of info about the swing group. It mentions the dipstick but doesn't even say anything about the grease point. It is in fact a zero tail swing. Yes, I failed to mention it was the swing transmission dipstick. I appreciate the responses. Neither of us are familiar with Komatsu machinery and his experience is all from much older, much larger machines 25T and up. We both suspect damage and we hope it's not the kind that requires tearing the machine in half to fix.
Here is a video showing the maintenance on standard house excavators. All excavators today are built along the same lines. You may find the check point for the grease tube in a different place because you have a zero tail swing, but it will still be in there somewhere around the boom pillar.
Thanks John. Good stuff. I will crawl around the machine a little better when I can in a few days and see if I can find some hidden stuff. I will update this thread if anything comes up
Ok gents, a follow-up as promised. I spent the last couple days crawling over the machine. Found 2 zerks on the outside of the ring that were so packed in dirt they were almost invisible. I also located the port for inspecting the bearing tub and found it full of water and contaminated grease. we spent two days clearing it out. I used an old spatula while my dad slowly swung the machine. I scraped as much as I could with the bottom port open and cardboard laying under and we did 4 flushes with diesel. a fill up and some rotation to agitate, dump, scrape, rinse, repeat. got a lot of rust flakes out. the slew gear has pitting all the way up and down the teeth faces and also has a little bit of a feather on the tip of the teeth where I could reach in and feel. It's not looking good. There is noticeable slack in the swing when it stops suddenly indicating that we have excessive backlash in the pinion to ring engagement. I believe there is also damage to the bearings if things are this bad but I can't fully prove that. Using the bucket on the ground and booming down to lift the house up, there is no noticeable slack or movement in the bearing that we can detect or observe. We flushed as best we could and put 160oz of fresh grease in the tub and ran it around. it's as good as we can get it for now. it still rumbles as much as it did before, no appreciable change in that attitude. On to what we think happened. When I was under the carriage, I found the underside packed in hard with river silt. the bottom of the engine bay is also full of river silt too so we think this machine was either used in flooded conditions, worked partially submerged in some kind of water feature such as a pond, or was simply in a flood and never cleaned out. based on how easy the grease pumped out of the bearing and presented itself by oozing out, I would bet that it would not be hard for the water to get in through that area if left long enough. we did not find any metal flakes or chunks in the tub or in any of the grease we pulled out. and we dug through it for a long time and used some strong magnets to pull metal and found nothing. I could not find any information in the operation and maintenance manual about adjustment in the swing machinery and was curious if the machine would have provisions for adjusting gear lash on it. I am planning on looking for a shop manual or something that will have more detailed information in it that can help but for now, all I can do is ask the question. Previous experience says if we can get the gear lash to a tolerable level, we may be able to extend the life of this machine some and it may buy us the time we need to get new gear, bearings, and swing motor gearbox or at least a new pinion for it. We think someone neglected this thing early in its life and it's sat for a long time this way. I have an old 72 Chevy truck that had been driven through water and then parked.. when I pulled the front bearings out to replace them due to noise, I found they had rust damage on 50% of the outer races and a definitive waterline.. the dry side had damage from all the chunks pounding through the bearing as I drove it until I discovered the problem. I think this is what happened to our machine.. terribly disappointed to say the least..
Good day Your experience is not that unusual as far as I am aware none of the hydraulic excavators have any flank play adjustment, I am afraid it is a case of replacing worn and damaged components. Maybe one of the other guys here can offer some suggestions. A contact has posted the specifications for the wear which I have attached and the method of measurement - replacement. Sorry my information will not bring a smile to your face only deepen your pocket. Kind regards Uffex
Thanks Uffex. To say the least, the language from my old man's mouth has been fairly colorful during this endeavor. we passed on good machines with more hours to get this one instead thinking it was a better deal overall. No way to tell now, the other ones could have been better, the same, or even worse.. such is the risk with buying used equipment you can't sit on and look over before reaching for the pocketbook. I have done some serious digging and found some places that have the stuff we need to replace these worn components. Not friendly on the pocket, but a sound machine will last ages when brought up to snuff. I will take these pdfs you've been kind enough to provide and add it to my stack of information to utilize to a better end. in the meantime, the damage is already done and we need to deal with it. I will probably be making some phone calls tomorrow to get the ball rolling on replacement parts and just bite the bullet. Thanks again for your advice and assistance! I will update this when we tie into this bearing and swing group replacement
Good day I just checked the specification I gave you is in fact a PC78 so that you are not have to check later mistaken listed as 68. Typing error while drinking the golden water. keep smiling Uffex
Sure thing, no worries. I didn't even notice the typo.. I was up too early after enjoying a few too many of the golden waters myself.
I have a line on a brand new swing bearing. My problem is that the part number for the new assembly ends with -48100 and my shop manual is showing 2 differing part numbers, -48101 and -48102. My machine's serial is showing part number -48101 in my recently obtained shop manual. a -48100 isn't even shown as an option. This is something I have noticed on most sites that are offering new swing bearings so I don't know if it's a generic number that is meaningless or if there is a legitimate difference between the different part numbers. He has one in stock and it ships free on an LTL right to the shop. I'd sure like to secure that thing.
Good day I do not have a parts book for your machine, however what I can tell you all rings made up of the following details -diameter - ball size - stud hole size and hole diameter. Maybe it is possible to call Komatsu and ask what those end numbers refer. I have checked our archives see attached information. Kind regards Uffex
For Komatsu, changes to the last digit in a part number indicate a minor change. Those might be a different supplier, some change in material or something like a grease fitting being a different location or size. Things change over time and parts books have no way of updating. If you want to be sure, call a Komatsu dealer and ask a parts person. They will be glad to help.
Thank you gentlemen!. I apologize for not responding sooner, logistics had me tied up and away from this side of the business for a couple of days. I have reached out to a nearby Komatsu distributor but they have not gotten back to me about anything. I was hoping I could rebuild the swing transmission myself if possible. I have two options outside of getting parts from a dealer. A Chinese gearbox for $1700-ish or a genuine Komatsu box for $3,500... a considerable difference. I would receive any advice one would have in that arena. I will continue to dig on this swing bearing part number chase