With and slipping belt issue under throttle I could only assume the belt tensioner was on its way out! so before it completely failed I thought it was best to change it. Whilst I was at it I took the opportunity to upgrade the Crank Pulley to a liquid filled ATI Super Damper crank pulley...the holy grail of crank pulleys!!

The tensioner can also be replaced from above which involves lifting the engine slightly with a trolley jack and removing the upper engine mount and bracket. Check out Driveway Buildz link below for this method:

   • Mini R53 Belt, Belt tensioner and idl...  

Links below for the pulley, tensioner and Laser tool pulley removal tool:

Tensioner:
https://orranje.co.uk/shop-by-car/bmw...

ATI Crank Pulley:
https://orranje.co.uk/shop-by-car/bmw...

Laser Tools crank pulley removal kit:
https://www.ebay.co.uk/itm/For-BMW-Mi...

Thanks for watching, if you have any questions feel free to ping them over!