I just lost the track on my Komatsu D21a. i found a leaking adjuster seal not holding the track in adjustment and a bad front Idler wheel bearing, not seized but extremely loose. Can i replace just the bearing or do i have to replace the whole idler wheel assembly?
The idler bushings, duo-cone seals and such are replaceable. Just takes time.
Is there a complete list of parts I can find?
Here are the part numbers you will need for one idler based on the serial number D21A-5 45005 up. What is your serial number? You would probably be better off buying an aftermarket complete idler group. By the time you buy all the parts and do the labor you will have more in the repaired idler. I'm at home now but I'll see if I can get the aftermarket part number. QTY 2 101-30-00091 • BUSHING ASS'Y Cast iron housing with bronze bushing 2 100-30-15120 •• BUSHING Bronze bushing only 2 110-30-00085 • FLOATING SEAL ASS'Y 2 101-30-00140 •• O-RING ASS'Y Oring for shaft 2 07000-03062 • O-RING Oring for cast iron housing 2 103-30-23140 • BOLT To hold block to shaft 2 01582-01008 NUT Goes with bolt 2 01602-01030 WASHER Goes with bolt James
I am here in Dallas as well and have both idlers off my D20 apart. Can you get just the bronze bushing or do they make you buy the steel sleeve which bolts to the wheel as well? Is it possible to build up the shaft with hard face and then turn down to spec? Also the seals can be lapped so they are water proof again. O-rings can be had from Hand D distributors.
Just as an afterthought. I am not making any money off my old machine so having it down is a big inconvenience but not a money loser. I do my own repairs because I could not afford to hire it done. And I must say that it is darn hard to find a decent mechanic especially one who would work as cheap as I do. I found that the D20 and D21 bottom rollers and the idlers take the same bushings and seals. I had replaced all my rollers a few years ago with cheaper aftermarket and kept the original Komatsu ones which seemed to still be holding their oil. This isn't hoarding if you can still use them!!!! I took the least worn rollers apart and cleaned up the bushings and reworked the seals which by the way take a special O ring. I have ordered 2 new shafts for my idlers because of the wear on the old ones I could not reuse and the roller shafts are different on the ends. I intend to put the salvaged bushings and reworked seals from the rollers in the rebuild of the idlers thereby saving 140 bucks each per idler. I had to heat the old wedge bolts and castings to get the idler assembly apart and in doing so pretty much trashed the wedge bolts. New idlers from Komatsu are $875 each and aftermarket around $450 -$475 apiece. I got the new old stock Komatsu idler shafts from T&E in Alabama. Their price was some less than Komatsu list but still way less than an entire aftermarket replacement idler and there was much lower shipping cost. I am going to have to break down and buy new wedge bolts because of how beat up they were when I took them apart. Even so it looks like I’ll still have less than $200 in each idler plus my time. That’s about 55 percent below aftermarket. Aftermarket is always a crap shoot since you never know what kind of quality your vendor is buying from. Case in point. I ordered aftermarket track adjuster piston cylinders from a local aftermarket supplier. Outwardly they looked ok but the interior walls had never been polished and still had very rough lathe marks on them. The cylinder walls must retain grease sealed in by a rubber piston ring seal which would have been torn up first time I used the machine. The vendor did eventually replace the part but the point is that I had to do the QC inspection myself. It’s a long way from the factory in China to the vender’s inventory. That assumes that the vender bothers to inspect what they are selling or even know what to look for. I am including some photos of the parts you would see if you took the rollers and idlers apart. D20 with idlers removed Old idlers removed Old salvaged roller, roller guts and end caps, seals and Orings Cleaned up and primed Idler casting
Here are some more pictures of the idler rework on the D20. A while back I noticed oil leaking out of various places in rollers and idlers. I thought I had solved the problem by inserting grease fittings in the leaky ones and keeping them greased. In hind site I would have been better off finding a way to inject 90W oil into them. The grease doesn't provide a slick enough lubricant film for the mating surfaces of the steel seal faces which causes them to spin inside the O Rings which tears up the o rings. The seal halves are a supper hard cast steel which are supposed to slide on each other oiled by the 90 weight. I hope that by lapping them with valve grinding compound on a flat granite slab will be sufficient to reestablish a good seal. That means lapping 8 seal halves. The worn shafts are supper hard heat treated steel and trying to build up with weld and grinding back down would weaken them enough to be a waste of time and money. Worn idler shaft and 2 part bushing showing bronze insert removed on rt hand side. Wedge bolts lock shaft in place when they lock into notch in either end. I will use these old shafts as spacers along with the old end caps when I build up the rail beams with weld to remove more slop. I'm not looking for perfection just a way to get another 10 years out of the old girl. old shaft and bushings showing locator notches on shaft. trashed wedge bolts. threads were to mangled to be reused. I will replace most of the fasteners used on the idlers and track because the bolt heads were so rusted that they were difficult to get purchase with a socket. I ended up driving a cheap throw away socket the next size smaller onto several heads in order get them to loosen. I did have to weld a big bolt onto one which was completely stripped.
my track cylinders are shot im pretty sure can you give some insight on can they be rebuilt, is there a kit for them and looks like a huge pain in the ass to to take out then put back in
As stated somewhere else here if you can afford to have a competent mechanic work on your machine then by all means let them tackle the job. I can’t for two reasons. One, I can’t afford any mechanics. Two, if I could afford a competent mechanic they would take one look at my machine and tell me that I don’t have enough money to have them work on it. My machine must have been used in a salt or fertilizer mine. The corrosion on the tracks has eaten a lot of metal and especially the bolt heads which I have had to weld extensions on to get any torque to get the old bolts out. The gas ax is the option of last resort because then you don’t have anything to grab hold of with your vise grips. As far as taking the tracks off and removing the idlers and the tensioners you have to be ready to do some work. I read a whole lot about taking the tracks off before I tackled that job. I was lucky because my tracks are the bolt together type as opposed to heat and beat type. There are enough of these grey market machines around now at various used parts places that you may be able to get a complete tensioner assembly for a reasonable price. It sort of depends on what blew out on your machine. Mine rusted enough where it would not hold grease and the spring broke. As far as the track tensioners, I only rebuilt the left one. The right one still holds grease. The left spring was broken as well probably leading to the cylinder failure. I got a new aftermarket track tension cylinder from a dealer in east Texas. The first one they sent me was junk but they did send me a better replacement. The first one did not have a machined finish on the inside of the bore and was rough enough to cut your finger if you ran it around it. The next one was better and I was able to use it with some extra work on the lathe. Price was right if you don’t count your time. I got a new piston rod / yoke made at a hydraulic shop because the old one was so rust pitted I could not use it. I bought the seals at a hydraulic seal dealer here in Dallas. They sell to all the rental yards and repair shops in the area. I had to make a special jig to take to the machine shop so they could press the spring back onto the assembly. They have a 40 ton press. The press at my shop is a Harbor Freight “12” ton special which is very wobbly. When pressing the spring on you want that done with no drama. Take it to a professional for assembly.
That idler looks like Berco design that Komatsu made under licence and were terrible. Check with Komatsu cause there is a design change. I had them on a forestry mulcher and could only get 1000 hours out of them. the new type has done over 3000 hours. They may be the same as they use on small excavators, about PC40 size.