Decompress track tension Komatsu D21A-7Pe

patvac · Feb 3, 2013

G'day,how the heck do you release the track tension on a Komatsu D21A-7pe?
I threw the rhs track off the sprocket in a steep little gully, I have lifted the rhs track completely off the ground, but I haven't got enough slack in the track to get it back over the sprocket....please give us a hand herw, thanx...

puckgrinder85 · Feb 3, 2013

The front idler is usually adjustable and it puts tension on the track with grease being pumped behind some sort of piston. So, you need to move that front idler in somehow. Im not exactly sure how its done but the grease needs to be removed for that idler to be moved. I would say remove the grease zerk and push the idler back in as far as it will go (will have grease flying out of that zerk mind you).
Once you get the track on you need to refill that area with grease to tension the track back up. That seem to be the standard track tensioning device on most machines i've seen.

puckgrinder85 · Feb 3, 2013

Heres a vid of what im taking about: Tensioning the Dozer Tracks - YouTube

banjodunn · Feb 3, 2013

G'day as said you need to get the grease out, if you follow the slide that the front sprocket sits in about a foot back from the edge of the main beam ( could be more) you should see a grease nipple that goes into a bolt head remove the whole bolt assy and you should be able to push the front idler in. If you have got an owners man it is the same nipple that you grease to tension the track
Oh and :welcome: to TBN good to see another aussie on here hope the rains up there aren't being too much of a hassle

Jon

DJ54 · Feb 3, 2013

I don't think you want to back it out real fast. There should be two holes that will relieve the pressure in that stud, if there is any spring tension left on the hydra-juster so go easy at first. Once the pressure is relieved, it may take a come-along to pull the front idler back far enough to jump the track back on.

patvac · Feb 4, 2013

Hey guys, thanx for for your valued help, sure do appreciate it....problem I have now is the large bolt that houses the grease nipple has two corroded bolt heads, so I can't undo the large bolt:thumbdown:

I thought once I undid the grease nipple and secured a 2 ton winch from the rear sprocket to the front idler,I should be able to pull the idler rearward and evacuate the grease from the cylinder....:thumbdown:

So now I am stuffed and fresh out of ideas

puckgrinder85 · Feb 4, 2013

Probably why the track fell off to begin with, wasnt ever adjusted properly.

banjodunn · Feb 5, 2013

G'day if you can get a single hex socket ( like an impact socket ) and drive it on the corroded bolt you may be able to get it out if not try a slightly smaller socket and drive it on if all this fails then try welding a nut on the corroded bolt.

Jon

patvac · Feb 5, 2013

Yep! you guys are right on the money.:thumbsup:
I can pump grease in which has put a lot of pressure onto the hydra adjuster. I can undo the large bolt that houses the grease nipple, but it is so very tight I fear that when I back the big bolt out to the final few threads, it may fly out under the extreme pressure I know have applied to the adjuster whilst trying to free it up. **** scarry

Hmmmm

DJ54 · Feb 5, 2013

There should be a couple smaller holes to relieve pressure, before it pops out. That is how they are designed, at least on one's I have operated. And it shouldn't really be tightened all that much, just a good firm snug should do it. Unless it is corroded, or someone really overtightened it.