the plastic chain guide is very very prone to breaking about half way down the front casing, it does not cause major damage to fix but the new parts to replace are the costly part as you need a locking kit for cams/ oil pump, also new plastic chain guide, adjuster units and all gaskets. all in all about £1200.....use only genuine parts. oh and some one to fit the parts......preferably a bmw specialist not average garage repair!!!! good luck