Kubota U55-4 Track adjuster keeps blowing a seal

[U55-4newbie]

Hi everyone,
Thank you so much if you are able to help, I need some help understanding what is happening with the RH track. I have had the machine for year and have no issues with metal tracks so far. However a week ago, the track adjuster blew its seal, so I replaced the seals, and there was some rust puckering so I lightly sanded it back before putting back in. It blew again straight away. This time when I pulled it out a metal shard was missing from the rod and was logged in the seal. (Not sure if I messed up here by using the bucket to release the grease from the tensioner, to take off the track?)
Then I replaced the whole track adjuster assembly. Its blown again.
The spring looks fine, no obvious damage. The idler seems to rock back and forth with the track movement. However, when I tighten the track, the idler on RH ends up being 10mm further forward then the LH track.
Could it be track issue? Or is it more likely the spring?
Thank you again.

 

[Cliffy]

Any vertical movement in the idler? Guides might be worn out

 

[Tones]

Check that the bolt that goes through the spring isn't broken. Also check that the track isn't worn out. Both causes the adjuster ram to over extend and damages the seal. The 10mm you've mentioned could be the difference.

 

[U55-4newbie]

Any vertical movement in the idler? Guides might be worn out

Thank you for your reply cliffy.

Just took a look, yes there is vertical movement, it 'jumps' as well as 'slides', although I don't think it is by much. Are they not supposed to move at all vertically? The LH seems to do the same but not as consistently, however I believe that is a function of LH being tight and the RH being loose.

And sorry, but when you say 'guides', do you mean c-channel that the idler assembly slides into or the fittings that hold the idler wheel?

 

[U55-4newbie]

Check that the bolt that goes through the spring isn't broken. Also check that the track isn't worn out. Both causes the adjuster ram to over extend and damages the seal. The 10mm you've mentioned could be the difference.

Thank you Tones.
How do I check the bolts integrity beyond a visual inspection? It looks solid. I read that shouldn't try to remove it from the spring/housing, any tricks?

I am working on trying to check how much the tracks are worn, but a lot of what is online has me more confused. The sprocket is wearing but the teeth still have decent shape I think, with a squared tooth. The pin casings on the track do have slight flat wear points on either side of them. But at what point do these become problematic or is it as soon as there are flat wear marks you have an issue?

Also, I didn't buy the tracks, they came with the excavator. How do work out what they are to find the pitch specs for them?

Again thank you!

 

[Tones]

Re the bolt, at a guess there should be a 10mm gap between the coils but pulling out the other idler will give a true comparison. I have replaced the bolt on site using the digger to compress the spring but I was out in the bush and miles from anywhere. It was sketchy to say the least but got it done without damage.
Re the tracks, measuring the distance between the pin centres gives the pitch. Don't be fooled by the external wear on the bush, most of the wear is between the pin and bush and can be seen by laying the track out on the ground and moving 1 end sideways. If it's bad but the rails are still in reasonable condition turning the pins and bushes is an option but is a job for a track shop who should be able to advice on the track specs.
Photos are always a help for others to make recommendations. (-:

 

[Tones]

1 other thing I forgot to mention, on many machines the spring mounting is offset ( not centred with the idler axle) and should be fitted into the track frame in the high position. This needs to be checked. Depending on how it's configured the adjuster ram will then want to tip in the barrel thus damaging the seal.
All of this **** comes from personal experience.