Astron Chain rattle

From Mitsipedia

Chain rattle is a common problem with Astron II engines. Most people believe that the problem is due to a rattling timing chain, but instead it is normally caused by slack in the balance shaft chain.

All Astron IIs can have manual balance shaft chain adjustment and in fact this is recommended every 20,000Km for older Astron IIs. Later Astron IIs can be adjusted but due to the self-adjusting mechanism the source of the slackness should be investigated.

Many have discovered that the self-adjusting chain rattles more on startup than the manually adjusting setup. This is due to the adjuster not having a "ratchet" like the timing chain tensioner to stop it from retracting when there is low oil pressure. Therefore at startup a slightly worn chain will rattle as it isn't being tensioned.