Description Reviews MINI Cooper Chain Tensioner ONLY. Part #11-31-7-607-551 or #11-31-4-609-482 are interchangeable. We highly recommend installing the full kit. This is the newest and up to date tensioner. This tensioner will will work on all the gen 2 cars with a N12 or N16 Cooper engine, or the N14 & N18 Cooper S engine. This tensioner is 82mm, which is longer than the older standard size 78mm tensioner. This part is also bilaterally exchangeable with part number 11-31-4-609-482 and we stock and have both part numbers because MINI will send us both depending on what they have in stock no matter which part number we order. Both tensioners are the same size and length with the same spring. We can't explain why MINI has two part numbers. MINI Timing Chain Tensioner. If you start up your car in the morning and you hear a rattling at start up or when it's cold out, then you are having a problem. Once it starts to rattle, it can jump teeth and cause the car to run poorly. It can even get so bad as to be off several teeth; and get to the point you cannot drive it without any check engine lights. We have seen the tensioners come loose from the block, the tensioners completely fail, the chain stretch (badly), as well as the car skips teeth, causing the timing to be off! If you don't want to do the whole kit you can try just adding this longer tensioner. But we still highly recommend installing the full kit. As an added benefit, we are cryogenically treating the tensioner. The cryogenic “heat treating” process is where the material is cooled to approximately −185°C (−301°F) with the use of liquid nitrogen. This increases the amount of martensite in the steel's crystal structure, increasing its strength and hardness. This in turn will not allow the chain to stretch or the tensioner to fail as quickly, if ever. This keeps your motor in time better as well as run more quietly and last longer with the proper maintenance. Note: Customer must keep oil in the car.