Based on your symptoms, I would pursue oil pressure. Your motor looks clean under the cam cover--like it has been taken care of (frequent oil changes), but the rattle at running temp and low RPM sounds like there's not enough pressure to actuate your chain tensioner. First things first, put a new and clean oil filter in it--aww heck--spring for a complete oil change with factory filter and oil. That'll give you a baseline to start from...

 

Sounds more valve train than piston slap to me. Possible that a sticky lifter is giving the rocker some play. Hard to check the oil pressure on a MINI, but if that was the problem I'd think you'd have noise from more than just that one corner.

Found this in another thread: http://www.enginebuildermag.com/2009...ppet-problems/

 

It has been confirmed as bad lifters. Just going to have the shop replace them all along with the camshafts as my extended warranty will cover it.

 

So, I got the Cooper back a few days ago and the rattle is completely gone. The shop just replaced the lifters as the Camshafts were still perfectly fine. We were able to compress both of the exhaust lifters on cylinder #4 by hand. All of the other lifters were in good shape but I had them replaced anyways. So glad this wasn't more serious and this will definitely be the last BMW/ Mini product I will ever buy.

 

All of this was with a new oil change and filter. It was 2 dead exhaust lifters that were causing the problem.

 

technically the n14b16a isn't BMW' it's Citroen / peugeot

 

But the rest of the car is BMW/Mini and riddled with ridiculously stupid problems that shouldn't plague ANY cars i.e.: license plate lights inop, drivers seat weight sensor malfunctioning, rear fog light socket won't stay in place even after complete plug and housing replacement, material quality is sub-par, and one day I noticed water dripping from my rear view mirror and the sunroof was completely closed and the windshield seal is perfect. And the aluminum sill plate on the drivers side just decided to peel up and get destroyed by the door and the rubber around the cowling and antenna mount are rubbish. Very high quality cars right here for sure...

 

In the three years that I've been on this form I've never heard of someone having bad lifters, the question you have to ask yourself is why do the lifters go bad? If your oil pressure is an issue it might stand to reason that some lifters are going to get starved of oil more than others do to the oil channels location. I'd at least cheak oil pressure at idle to be certain.

 

I am the second owner of a 2012 Cooper Hardtop with 25K on the clock, and the lady that owned it from new was very meticulous in its upkeep, but the oil changes were done by BMW Cincinnati at BMW's recommended interval, which in my opinion is far too many miles apart, even for the best fully synthetic oil.

I suspect that many of the problems such as the bad lifters mentioned above could be owners that have followed BMW's service intervals.