With the R53 MINI, it’s not a question of if, but when the belt tensioner will fail. If you are lucky, it just doesn’t provide enough tension on the belt; the belt slips, and you get a code telling you something is wrong. If you aren’t lucky, the damper machines into the crank pulley (see this post ). (In the photo below, the tensioner damper failed and rotated into the crank pulley, machining off parts of the crank pulley in the 30 seconds it took to pull off the highway to check.)

You should regularly check the health of your belt anyway and replace it every 30,000 miles or two years (more often if you track your vehicle). A stretched belt is relatively easy to spot.  Just observe where the spring retaining clip passes through the tensioner body.  There should be at least half of a circle visible.  If not, then it’s time to change the belt. (See inset in the photo below.)

Tensioners fail when the belt breaks, causing the retaining clip to fail or when the bushings on the damper get worn and the damper fails. Unfortunately, the condition of the tensioner itself is hard to observe. Once you lock the tension on the spring, try to feel for lateral movement in the damper.  You might be able to see the front side of the bushings if you look carefully from above the motor mount.

You should consider replacing your tensioner every 60,000 miles or 4 years. And if you’re replacing the tensioner anyway, consider upgrading the bushings and adding a tensioner stop at the same time, since they’re both much easier to do before you install the tensioner on the engine.

Start with a new stock tensioner and remove the two 13mm bolts that hold the damper.  Check that the damper is functioning by compressing and extending it.  There should be resistance, but smooth movement.  Remove the two stock rubber bushings by gently pressing them out of the damper ends.

Install the Powerflex Poly bushings using the supplied silicone grease.

Since the Powerflex bushing ends are slightly larger than the stock bushings, press the Alta Tensioner stop over the end of the damper before installing the damper on the tensioner. And check for fit.  You want to ensure the open end of the tensioner stop can move freely on the end of the damper.  Be sure to also use the rubber piece on the arm to reduce vibration noise. Tighten the bolts but do not over-tighten.

Now you’re ready to replace the tensioner in your car. Be sure to replace the belt at the same time.  Pelican Parts has a great DIY write-up if you haven’t done it before.  Give yourself more than 2 hours and even though the engine has been raised, it is still a terrible place to try to wrench. Patience and gloves will spare you busted knuckles. Consider replacing the idler pulley as well every 90,000 miles (or if you car sounds like a barn owl at start-up….)