I had to replace the liner, piston and rings in one cylinder do to the rings coming apart from being stuck after sitting for 20 years, the new liner sits where it should now but the other three have dropped over the years which I now know is a common issue with wet liners, the other cylinders have great compression and I don't want nor have the time to replace them as well so I'm wondering if anyone has had this issue before and if so did the head gasket hold up or did it leak and if it did leak were they able to correct the issue somehow? Thank you in advance for any help that you may provide 

Oooo good question ❔ I have two 12A 955's that I need to rebuild.
FYI: The D315 apply to the same Cat s/n changes but the undercarriage changed {as per Old Magnet} "C" to "E" model included a change from D4 size undercarriage to D6 undercarriage at s/n 12A05793.

Did you remove the very thin seal washer under the lip of the liner? Been there done that. Clean the block with a small wire wheel on a die grinder, it looked all nice and clean. Assumed the ring was still on the old liner. Head gasket leaked until the sleeve was removed and the extra ring removed. Mine was a 318 rather than a 315 but I believe the same design just 2 more cylinders.

   Yes sir Ray I did all of that my issue is the one liner i replaced is sitting as it should, at the correct height my concern is that the other 3 are lower than they should be due to vibration over the years, the outer lip is flush with the block. I had to replace the head gasket before I could ever getting it running enough to move it which there could be many reasons it was already blown but I am very concerned that it will for sure blow it again with the one liner sticking up higher then the other three. Or am I worrying for no reason, am I better off with one liner at the right height than none at all? In my mind I'm thinking it's going to cause a gap somewhere what would be your Thoughts on that? I'm going to be installing the head today or tomorrow then I guess I will know then as I don't see anyway to do anything about it so I hope it works, thinking I will do a compression test before I finishing everything else I had to remove do to I being a traxcavator and not just a dozer, the extra frame design meant I had to removed all of the fuel component's which I didn't so much mind as it gave me the chance to look everything over real good. going to include some photos of the machine from where it was sitting to now for everyone to see how far its come so far. Thanks again for the help and any other as well.  she is almost full repainted now this photo was a few weeks ago.

Thank you Dan for the info.

These general rules apply, anything less is asking for trouble!!!!!
 
 

No idea other than what OM just showed. Hopefully the liner might go down a bit more. Just a poor farmer that did not have funds to just call a mechanic. And I was surrounded with some very sharp mechanic that put up with my never ended questions ..................mostly. And most of the bunch are all gone now.

Looking Good - you have come a long way!

I might suggest a metal stop between the cylinder body and the pin to the attachment (buckert arms). Be much better than a 2x4 to support that loaded frame when you are working in and about it. Something that you could easily fabricate and there are many examples from Dump Truck beds to heavy equipment. A requirement in most of todays applications.
You should be able to find examples on local equipment yards, dealers.

cts

If you're thinking of replacing your seat cushions, I recommend Zane Meinberg who took over Hahn Seats. He built for me a seat for a 4R D6 and a Diesel Forty - both exactly to spec. The workmanship is excellent.

The rule of thumb i always worked to was 1 to 4 thou liner height above block. There should be no more than 2 thou difference between liners beside each other. Most machine specs will say 0 to 4 thou. I guess you’re three liners are at 0 when you say they are level with the block. What height is the new one. If it is at 4 thou you could take 2 thou off the sleeve where it sits on the counter bore to get it close. Good luck the rest of the job you have done looks great.