[URL="http://http://m.youtube.com/watch?v=d4qKEmJTGXY"[/URL]

I've spent the last several hours perusing the forums on several websites to little or no avail. I posted the link to a YouTube video of a N14 engine making the same sound my n12 is making. It's a redudent knocking sound that disappears when driving (or at least I can't hear it). I can only hear it when the car idles and it sounds like it's coming from the left back side of the engine (if facing front of car). I don't think it's the timing chain tensioner as the knocking sound does not change when driving or when pressing the accelerator. It's literally not noticeable at all when driving the car. It also doesn't appear to be a rod knock as the sound of a rod knock would get more pronounced with increasing RPMs?

Long story short. I went to pick up my 2010 mini after signing the paperwork to purchase the vehicle and heard this knocking sound. It was cold today in northern New Jersey (32 degrees) and it snowed earlier today. When I initially test drove it last week, it was almost 65 degrees outside. I did not hear the knocking sound when I test drove the car last week. Also, the knocking sound did not go away after 10 minutes of driving and probably another 10 minutes of idling.

The purchase contract stipulated that the dealership change the oil, brake fluid and serpentine belt. All of this was done prior to me going to pick up the vehicle today. Could the pulley be loose? Not sure what would be causing a knocking sound at idle that isn't prevalent while driving. Of note, the car is an automatic.

Long story short again - I refused to give them my down payment and asked them to reverse the transaction. They seemed willing to do this and also said they were going to have their mechanic look at the car. I'm not sure if this knocking sound is a huge red flag and a sign that there's an underlying issue with the engine?

If anyone has any useful input, it will be greatly appreciated.

 

I also have a 2010 MCS with a similar sound but no as loud, I first I thought it was the timing chain but after reading a lot as well I found a Service Bulletin from BMW, the one they use to diagnostic the timing chain at the dealer. Basically what they do is to disconnect the right vacuum hose coming from the mechanical vacuum pump, if the knocking noise goes away then is not your timing chain and the knocking is considered normal, they don't even recommend to replace the pump. I know is weird but that's what the bulletin said.

Search a little more regarding diagnosing the timing chain and you will find it.

 

Thank you for replying!

I found what you're referring to. Not sure if this is the issue as the sound appeared to be near the TC. I'll mention it to the dealer's mechanic tomorrow and have him perform the test. However, it was not a rattle sound. It was a true knocking sound (very similar to rod knock), which is why I didn't think it was TC related. Ive watched several death rattle videos and it sounds nothing like the death rattle.

 

It actually sounds a lot more like this.

 

The sound on your video sounds like a possible issue with the timing chain and/or tensioner, so that's where we'd recommend you focus your attention. I would definitely have this corrected before making a purchase or payment, and try to receive a warranty on any repairs should the issue return again in the near term.

 

It's perfectly normal, a lot of new owners come here with similar concerns about the dieseling sound do to the HPFP. However these N14 engines typically can have lots of issues, you're better of with a more reliable car!