Buzz Sound when the engine is cold?

Mine did this once a few months ago when it was really cold. Sounded awful. Then it has done it again twice since I got my oil changed last week. Cold starts after really short trips seem to set it off in my case. If it keeps doing it, I'm going to the dealer as well.

Take it back to Cincy MINI. Maybe they can fix it.

Hi guys! Stumbled across your MINI forum whilst (love that Queens' english!) cruising the MINI Internet world. We have a family of MINIs - his and hers 2007 MINI Cooper S coupes.

Judging by the above posts, you guys are not up to date on the status of the cold start "death rattle" exhibited by '07-'09 turbo-powered MINIs (and Peugeot cars with the same engine).

After 2 years of denial, BMW has admitted that, yes, the timing chain tensioner design is defective, and has started a "silent" recall of all affected cars. A bit of history first. After a raft of owner complaints about an awful rattling noise coming from the front of the engine during the first start of the day, BMW first told the service advisors to tell customers that the noise was "normal". It appears MINI meant to say the vacuum pump chuffing was normal, but it was misinterpreted at the dealer level. Then after irate owners with a lot of auto mechanical background began storming the dealerships with pitchforks and flaming torches, the official word was "It's normal for the engine". Then reports started rolling in about broken timing chains, destroyed chain tensioners, lemon law buy-backs, and many, many replacement engines. With this engine design, a broken timing chain will result in catastrophic destruction of the engine.

BMW has tried three revised versions of the timing chain tensioner. The June '08 and Nov '08 versions did not cure the problem. I had the Nov '08 version installed to silence the morning death rattle - a waste of my time.

The current fix was released Feb 2009. This involves an entirely new tensioner design. The previous versions relied on engine oil pressure to apply tension to the chain. The root problem was that the hydraulic piston (powered by engine oil pressure) that pushes the tensioner face against the chain did not extend, or extended partially. To make matters worse, the tensioner piston would drain its internal oil supply over long (overnight) shutdowns and fill with air. On start-up, it takes 1-2 minutes to purge the air. Most of you with the "death rattle" have probably noticed it takes a minute or two for the rattle to go away. Now you know why.

The latest repair involves a new tensioner that incorporates a stout spring to hold the tensioner face against the chain until oil pressure is adequate. Initially, dealers were to just install the new tensioner, measure the existing chain for stretching, and if within BMW's limits, send the customer on their way. Fortunately, US MINI dealers rebelled, forcing BMW to now replace the entire timing chain system. Everyone with a noisy 07-09 turbo-powered MINI will get a new tensioner, new timing chain, chain guides, all sprockets, and a new Vanos unit (the gizmo that adjusts the intake valve camshaft's timing). The job takes two shop days, and the right front wheel inner liner is removed to provide access to the engine front. The new tensioner will be in all new or rebuilt engines beginning in March '09.

Here's some links for more info:

A great explanation of the design by the guy who designed the valve system for the '02-'06 MINIs www.michiganmini.org/forum/index.php?topic=3115.msg88780#msg88780

A diagram of the affected parts: www.realoem.com/bmw/showparts.do?model=MF73&mospid=50031&btnr=11_3924&hg=11&fg=25

The BMW repair directive to the dealers is PuMA measure number 10686850-13, released on 2/24/09

The part number for the new version 3.0 tensioner is 11.31.7.598.956.

I hope this gets you guys up to speed on the status of the MINI Cooper S morning start "death rattle" issue. By the way, the standard MINI engine has an entirely different cylinder head and valve design, and does not have the "death rattle".

Hats off to oldmgguy. I will be talking to my dealer about this issue very soon.

The dealership is supposed to install the latest timing chain modifications when installing a replacement engine, since that particular engine may have been sitting in the box for quite some time. Ask your service rep if they did so. Use the PuMA number quoted eariler as your reference, and they should have replaced the entire timing chain system on that boxed motor.

Looks like you hit the 3-week window where they installed the new tensioner only. They should have measured the slack in your timing chain and obvously deemed it within specs. The concern that forced a full replacement of everything was potential liabilities as the cars accumulated mileage and then the chain broke, due to initial minor damage that wasn't observed earlier. After all, the rattle is the acoustical signature of metal parts whanging against each other at speed. In this engine, a broken chain results in catastrophic engine failure.

So far, I haven't seen any negative comments by owners who had just the new tensioner installed. Time will tell as to the damage, if any, to the chain and sprockets.

Definitely get back to your dealer and discuss the latest revised procedure. Request and get it noted on your service record that you want the full procedure done. Won't cost the dealer anything if BMW says "OK", and the techs could certainly use the income!

;D Cool - Another MINI family! We've got a pair of '07 Cooper "S"s, his and hers. Mine rattles like a diesel after it sits for 5+ hours, the wife's car starts and purrs like a Honda every time. I'm scheduled to get the new "Replace everything" fix later this month.

What's happening here is that the tensioner piston is supposed to remain in it's last position by internal seal friction. A significant number of the pistons are defective and slowly collapse back over time. The latest tensioner design now has a spring to hold the tensioner face tight against the timing chain until oil pressure to the piston is adequate. Just like the 58-year old chain tensioner in my 1951 MG!

The standard MINI engine has an entirely different cylinder head and valve design, and has not exhibited any chain rattle issues to my knowledge. Nothing reported on the various US and UK MINI forums, anyway.