My 2008 Mini Cooper S makes a weird rattle right at startup and goes away quickly.. should i be concerned? WTF is it and can i fix it?!
Shep

Absolutely. Most likely it's going to be related to the timing chain and/or timing chain tensioner. Either way I would def get it checked out ASAP.

Dammit! How much is that gonna cost?

Brace yourself, this is not going to be good news.....

http://www.mini2.com/forum/second-generation-faults-fixes/136105-mini-cooper-s-engine-noise-when-cold.html

Read up on this first, so that you will probably know a lot more about it than your mechanic does before s/he starts to extract large quantities of ca$$$$h for you simply trying to work the problem out for him or herself :(

To be honest it's hard to tell without going in and measuring the timing chain (this is per MINI...). If you're getting it on cold start only and it quickly goes away and you get it looked at soon it may not cost you all that much. Sounds like it's just the tensioner not the whole timing assembly. I'd take it in as soon as you can and have them check it out.

I admire your optimism there.

However, I have followed the experiences of friends whose MINI's have developed this problem and followed the story on line for the last 5 years. Some cars have had tensioners replaced as many as 3 or 4 times with no beneficial results.

I agree with you there. The main problem with that is the fact that the fix if the timing chain tensioner is bad and it is caught before the chain stretched out too much (again this is per MINI), is a slightly longer/stronger tensioner. It's not a huge difference but maybe 3-5 mm difference in length. However, in my opinion this is just a bandaid over to prolong the life of the chain. Ultimately it WILL stretch too much and require a new chain assembly after a tensioner replacement.

Being a MINI tech by trade, I do notice alot of the problem (and I know this doesn't go for everyone and know plenty of MINI owners that stay on top of these things) is people not checking their oil regularly and allowing it to fall too low, too often. The timing chain tensioner operates off oil so if there's not sufficient oil in the car it can casue premature wear and failure of the tensioner.