My Countryman now has 170,000 km (105,000 miles). I've noticed that a great deal of timing chain issues seem to start with the upper guide rail failing and parts falling into the timing chain area. Although my car does not display any timing chain related issues, would it be a good idea to replace the upper guide rail and chain tensioner. I have no reason to remove the valve cover other than to possible do this.

Thoughts?

* note that my Countryman is the base model N16 engine

 

Just the tensioner will do. All plastic guides are prone to failure but usually only after the chain has been slapping around for a while or breaks. Check Realoem for the latest part number for your motor. Mine is in Rev 3 and was 5mm longer than the part I replaced.
There is a school of thought that the whole chain/guides/sprockets/tensioner kit should be changed at 100K miles. if you can find someone with the right tool, you can measure the chain stretch when the tensioner is out. Anything over 68mm needs a new kit and full replacement.

 

Thanks for the info. I checked realoem and for the tensioner part# 11317607551. I don't know what Rev that is but it is 82mm long. I will plan to change the tensioner and see if I can find someone locally who can measure the stretch.