Track adjuster won't accept grease

[carguy]

Komatsu PC60-7 lost a track, so loosened the adjuster nut and let grease come out as I pulled the idler sprocket. Got the track back on but now I can't get grease into the adjuster. The zirk fitting is free. My hand grease gun should generate enough pressure, correct? Are there any tricks for forcing the adjuster to tighten?

I can use my bucket to pull the idler back out and the track will get tight but still can't get grease in there, even with the idler extended.

 

[kshansen]

I know nothing about those adjusters but I was wondering if there was a valve of some kind that has to be opened to let grease from zerk to flow to the adjuster? Or is the zerk in a fitting with a check valve in it. Seems like trusting the little ball in a zerk to hold all the pressure would be asking a lot of the little thing.

 

[carguy]

I'm no expert either but I'm pretty sure that zirk fittings have a one-way valve...there's a little ball in the end to prevent grease from coming back out. I mean, they use them everywhere to push grease into tight places. But there's a lot more to this issue than the zirk...if you look at a parts breakdown of these adjusters it's more complicated and I can't picture what's stuck inside there.

 

[Nige]

I'm no expert either but I'm pretty sure that zirk fittings have a one-way valve...there's a little ball in the end to prevent grease from coming back out.

Track adjusters generally don't work that way. There is usually a screwed valve below the zerk that has to be opened before grease can be added, there is often a second screwed valve that is used to remove grease from the assembly. IMO the ball in the end of the zerk alone would not be adequate to withstand the load of impacts on the idler/recoil mechanism over an extended period of time without failing. Also if the system relies on nothing more than the ball in the zerk as a non-return valve for the grease how are you expected to release the pressure in the track adjuster in a controlled fashion.? Not by removing the zerk surely.?

Sounds like you have the parts breakdown. Can you post it up.?

 

[A. Williamson]

Nige is right. I once had a united rentals mechanic install the check valve backwards on a ditch witch and he had the same problem as you.

 

[Tones]

The zerk is screwed into what looks like a bolt head. Loosen the bolt ( 1 turn max) then try to adjust the track. Retighten the bolt when you have the correct tension on the track.
To loosen the track unscrew that bolt until grease starts coming out . Do not remove it with tension on the track, it could hurt you.

 

[Bluox]

Every one of these I have seen the grease fitting is part of the release valve and the ball holds the grease in.
A lot of the adjusters also have a separate release valve to allow grease out of the cylinder.
I mean what could the surface area of that ball be 0.0002 sq.inches?
Bob

 

[A. Williamson]

I mean what could the surface area of that ball be 0.0002 sq.inches?

Surface area of a sphere is 4pi r^2 so you're off by a couple decimal points. Figure maybe 1/2 the ball is getting grease contact so its ~0.025sqin for a 1/8 ball

Edit correct typo

 

[A. Williamson]

But that's pretty big for a grease zerk isn't it. A 1mm ball would be 10x less surface area

 

[John C.]

The fitting does not have to be loosened in order to add grease to adjust the idler out. There is a check ball and spring inside the track adjuster fitting that takes the load. The front of the fitting is a cone that seals the grease in the cylinder. Turning the whole adjuster fitting backs off the cone which allows grease to pass through a relief hole.

The common problem with these is dirt getting forced around the track adjuster cylinder and hardening in the bushing inside the cylinder. It happens because the chains are stretched out and the idler can bounce around in the track frame which creates a space around the track adjuster cylinder rod and cylinder head for dirt to get shoved in. You should have pulled the adjuster cylinder apart before you put the track back on. You would have found that you couldn't get it to move at all and will likely have to scrap it and get another one. I have actually chained each end of an adjuster to two D6 sized dozers and all they did was spin their tracks.

 

[carguy]

The fitting does not have to be loosened in order to add grease to adjust the idler out. There is a check ball and spring inside the track adjuster fitting that takes the load. The front of the fitting is a cone that seals the grease in the cylinder. Turning the whole adjuster fitting backs off the cone which allows grease to pass through a relief hole.

The common problem with these is dirt getting forced around the track adjuster cylinder and hardening in the bushing inside the cylinder. It happens because the chains are stretched out and the idler can bounce around in the track frame which creates a space around the track adjuster cylinder rod and cylinder head for dirt to get shoved in. You should have pulled the adjuster cylinder apart before you put the track back on. You would have found that you couldn't get it to move at all and will likely have to scrap it and get another one. I have actually chained each end of an adjuster to two D6 sized dozers and all they did was spin their tracks.

Appreciate the info. Question I have now is what exactly does the track adjuster consist of? Is it the entire (expensive) assembly including the spring or is it a smaller cylinder in the back that accepts the grease? Is there no way to take it apart and clean it rather than buying a new one?

 

[John C.]

Now you are taxing my memory. I would suggest that if you don't have a parts book to get a Komatsu dealer parts guy to email you a copy of the page in the book. A couple of machines I did have to replace the whole set up, spring and all. I just can't remember which ones.

To take it apart, the cylinder rod just pulls out the end of the barrel as I recall. The problem is you are able to pump 10,000 PSI with a normal grease gun. If the piston is one inch in diameter, you are able to put about 15,700 PSI of force pushing the piston out of the barrel. That's a conservative estimate of what it will take to get the adjuster apart.

 

[Nige]

The fitting does not have to be loosened in order to add grease to adjust the idler out. There is a check ball and spring inside the track adjuster fitting that takes the load.

Thanks for confirming that John. I couldn't see how a track adjuster would depend simply on the ball in a grease zerk to hold the pressure.

 

[biggerhammer]

Kobelco adjuster fittings are bad for not taking grease if a spec of dirt gets behind the initial check valve on the zerk-replaced lots. Take the fitting right off and see if grease flows freely-if not the cylinder is dicked. Sometimes you can disassemble by welding an on the end and yanking it out-put a new rod in cause it'll be damaged-clean all the corrosion in the tube and reseal. When I see it this bad, I like to replace the entire assembly and be done with it

 

[carguy]

Kobelco adjuster fittings are bad for not taking grease if a spec of dirt gets behind the initial check valve on the zerk-replaced lots. Take the fitting right off and see if grease flows freely-if not the cylinder is dicked. Sometimes you can disassemble by welding an on the end and yanking it out-put a new rod in cause it'll be damaged-clean all the corrosion in the tube and reseal. When I see it this bad, I like to replace the entire assembly and be done with it

I have had the zerk fitting off, and I loosened the big nut the fitting screws into. No grease came out of the zerk hole but some did come from around the big nut, when I pulled the idler backwards. So the idler is back pretty far now. Doesn't this imply that there is movement in the cylinder? Why else would grease come out?
Then I pulled the idler forward far enough to tighten the track, thinking it would then be easy to get grease in, but that didn't work. As soon as I release the forward pressure from the idler it returns to where it was and the track is slack again.

SO....if I try pulling the cylinder out as you say, how do I get at it? Could I screw in an eye bolt in place of the zerk fitting and yank on that? I'm thinking run a cable through the eye and use the bucket to pull rearward. (I also assume that the large nut would have to be unscrewed first.) Or is this all done only with the entire assembly removed from the machine?

 

[Bluox]

Pull the big nut fitting out and see if you can pump grease thu it with the grease fitting back in it.
Bob

 

[kshansen]

Before doing much more I would want to have at the very least a good parts breakdown or preferably an actually factory service manual. Just guessing at how something works or comes apart can be costly or even deadly!

 

[A. Williamson]

As soon as I release the forward pressure from the idler it returns to where it was and the track is slack again.

Sounds like you're creating a vacuum when pulling out the idler like no air can get in the cylinder while you're pulling. Some kinda blockage going on not that that wasn't already clear just saying

 

[carguy]

Before doing much more I would want to have at the very least a good parts breakdown or preferably an actually factory service manual. Just guessing at how something works or comes apart can be costly or even deadly!

ing
Here's a parts breakdown from the repair manual. "Creating a vacuum" is an interesting thought. I will remove the zerk fitting before I pull the idler out and see what happens.

 

[Nige]

That disassembly & assembly procedure is for the recoil spring assembly, not the tensioner. The tensioner sits behind what's shown in the illustration above.