2010 Justa with 28K miles. This week I tried a new dealer (Herb Chambers in Boston, MA) because the original dealer (Inskip in RI) was unwilling to address under warranty a chronic loud rattle coming from the engine/trans unit area. It started at 5K miles. They have claimed to have "no idea" what is causing this, but that they have been willing to start taking the car apart and if they "found" something that was covered under the warranty, they would cover it. Otherwise, it would be on me. Not a very appealing option.

Herb Chambers diagnosed the problem as an upper trans mount issue and have ordered one. We will see if this takes care of it.

On to the main point of this post:

With some MCSs having timing chain failures with as little as 30K, concern is unavoidable. The N14 and N12 do not appear all that different on the surface, but who knows? I offered to pay HC for the labor to install ST 11 9 340 and measure the timing chain slack.

They did so and came up with 65.54 MM. According to BMW TSB SI M 02 07, this would call for installation of the longer tensioner, P/N 11 31 7 607 551. If the slack is more than 68 MM, the TSB calls for replacement of the entire assembly (chain, guides and a different tensioner, P/N 11 31 7 597 895).

However, I was told that this TSB is ONLY for the N14 (I have an N12) AND that this TSB has recently been superceded by a "case by case" policy where they no longer use rigid guidelines to decide what action to take. "BMW engineering" decides and tells the dealer what to do

Also, N12s reportedly have "no history" of timing chain issues. The shop foreman offered that I "might need a new tensioner at 100K miles", but at this point, the only thing they could do was reinstall my existing tensioner.

In all, the HC service writer and shop foreman couldn't have been nicer in their manner and they ended up not charging me to remove my tensioner, install the special tool, measure and reinstall my tensioner. They recorded my tensioner part number (75978958002) from the actual part. Note that this is different from either number listed in the TSB. (I don't know if "package" P/Ns differ from what is stamped on the actual part.)

I plan to check it again at the annual service next year and see how much additional wear has occurred in what I expect will be another 15K miles (unless, of course, it or I croak before that).

Unfortunately, I have not been able to find any specs as to what a brand new chain and guides should measure in terms of slack on an N12, so there is no way to know how much combined wear has occurred in the first 28K miles.

At some point, it would be nice to install a longer tensioner to handle the gradually increasing amount of slack, as is routinely done with the N14, but that kind of thinking is probably too "out of the box" for the BMW hierachy to deal with.

If the slack exceeds 68 MM in a year, it will be interesting to see how things develop at that time.

So, any thoughts?

DOC

 

They were correct when they said that the timing chain TSB only applies to the N14 engine.

Also the measuring of the tensioner, while a nice gesture, doesn't really apply to your engine either, meaning that the valvetrain and all cylinder head components are different on the N12 and N14. Therefore meassuring the "slack" on an N12 engine, when the procedure was intended for a N14, doesn't really tell you anything.

As the proactive owner that you seem to be, just keep an eye on your engine oil level and I would highly recommend you perform an oil service every 6500 miles or 6 months. This is pretty much the only thing you can do, sorry.

Happy Motoring!

 

Hello Joey,

It's great that someone who specializes in 2nd Gen timing chain repairs has replied. Really appreciate your input. Where on the globe are you located?

1. So what should the timing chain slack measure on an N12 with a brand new chain and guides. (The tensioner does not matter because that is not installed when the slack is being measured.)

2. At what amount of slack do you think the "longer" tensioner could/should be installed? At what amount of slack should the chain, guides and tensioner be replaced?

2. Besides the DI, CR and turbo, what is different between the N12 and N14? The chain, tensioner and guide photos in the Bentley manual don't look any different that I can see. My N12 has the same "zing" on startup from the chain dragging until the oil pressure builds up that is mentioned in the TSB.

Several people have noted that they no longer get that "zing" on cold startup after installing the P/N 11 31 7 607 551 tensioner (presumably on MCSs). I suggested an Accusump to the dealer to address this and was told that would void the warranty.

I have changed the oil and filter myself every 5K except for the Mini "annual service". (I use 00W-40 Mobil 1.) (BTW, I had a pretty loud case of "death rattle" when it was brand new. At 1000 miles, I switched to Mobil 1 and the "death rattle" went away. I attribute this to the slightly thinner Mobil 1 allowing the tensioner to pump up more quickly than with the Mini/Castrol 5W-30.)

Thanks for your input!

DOC

 

Hey DOC, thank you for the kind words. I'm located in Lorain, Ohio and I have been a BMW technician for the past 7 years. I can honestly say that I have seen pretty much every major MINI issue that has come across the line.

As for the timing chains and N12 engines, I'll be honest, i have only done three since the cars came out in '07. All three were caused by the vacuum pumps seizing up and locking the engine and all three vacuum pump were damaged by lack of oil lubrication.

These three owners apparently thought that going between 17-21k miles between oil changes was not only ok(which by BMW it is) but that they didn't even have to check the oil level on a regular basis - therefore all three were extremely low on oil (one had only 1.25qts of oil in the pan) and none lubricated the rotating assemblies as suppsoed to. Due to the fact that they hadn't really broken any warranty issues, all three repairs were done under warranty.

As for the "slack" of the timing chains on the N12, I'll be honest again and say that I have never tested a car off the delivery truck, in order to determine what a perfect engine meassurement should be. I can tell you on a N14 that 62-63mm is the norm and that is because I have done many different tests on those engines.

As an N12 owner, you will be happy to know that your engine has been really good in regards to internal mechanical issues. As I have posted on another thread, the N14 biggest issue is the consumption of oil by the turbocharger, paired with the long oil service intervals and the lack of owner care when it comes to topping off the fluids.

As for the difference between the N12 and N14:
N12 engines have Valvetronic on the intake cam along with Vanos on both cams -- N14 only have Vanos on the intake cam. This along completely changes the dynamics of the two engines and thats besides the obvious things like turbocharger, direct injection, high pressure fule system, low/high compression ratios and all the related components added to those systems.

Hope this helped!

 

So you work for a BMW/Mini dealer and also in your own shop?

If 62-63 MM for the "slack" measurment is normal for an N14 after installing a new chain, guides, etc., I suspect that an N12 would probably be similar. At 28K miles, my N12 motor is at 65.54 MM

Can you find out if it would be OK to install the P/N 11 31 7 607 551 (longer) tensioner on an N12? In another year (probably 14K more miles, 42K total), I expect the slack measurement to be about 68 MM, or when an N14 was previously scheduled for a "full" timing chain, guide, etc. replacement.

If OK to use, my hope is that the longer tensioner will allow me to get to 100K without skipping a tooth and lunching the motor. I am already budgeting for timing chain, guide, tensioner, water pump replacement at 100K, just as one typically would with a motor with a timing belt. Not thrilled about this, in part because I expected a motor with a timing chain to not require this sort of extremely expensive periodic service. (Local independent Mini shop charges $1400, Mini dealer $2200.

Again, really appreciate your input.

DOC

 

I will look into the tensioner and I'll let you know.
Happy motoring!

 

I know this is an older thread now, and I've posted this on other threads that I find by searching "N12 timing chain". I've been moved to get a baseline on my 2008 Cooper after 6 years and 65,000 miles, so yesterday I finally got my new tensioner bolt and my slack measurement: 69 mm. It made me glad to have done the measurement. Cost came to about $300, and I will include this as a "repair" next time Consumer Reports sends along their survey.
My Mini has had the best possible oil and maintenance care all along, so this is a design issue. Some of us are missing the old timing belts now, but they must be replaced every 6o k or else. A friend of mine lost his Saturn that way. Still, you'd think that the chain would be a done deal, vs. a regular worry.