Car came onto our forecourt with complaint of noisy and not running right. A quick listen indicated a misfire and code read agrees but also with cooling issues and low fuel.

Not a major problem at the moment but my concern is on start up and switch off a knocking can be heard at first from iside the car i thought it was a DMF failure but under the bonnet the noise is all from the top end at the front of the cam covers nothing heard underside so prob not crank pulley.

My question is not knowing this engine is this likely to be how it is (wouldn't think so as it's so loud) or how sinister is it likely to be.
Any help would be appreciated
Thanks in advance
Kelly

Does it have Vanos?

The S85 has double vanos.

Matt

Yes it has double vanos and that is where the noise sound as if it is coming from. Am waiting for customer to bring in service info as he thinks it was not so long ago the oil was changed, hoping this may be an issue ie wrong oil, but what damage may have been caused?

The M5 does suffer with vanos noise - its just one of those things. there is a lot of "myth and legend" surrounding vanos but because its noisy does not mean its not working. Its usually always worse when the engine is hot and around idle speed and is at its worse when the engine is blipped and the revs fall back past ~1200-1400rpm.

If it hasnt thrown any codes then its probably fine and an oil change with the correct oil will help, although as the oil ages the noise will get louder again (think of it as an audible service indicator ).

Kelly
As the correct oil is about £20 a litre, incorrect oil a good possible.
Kev.