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I've read all about the dreaded timing chain failure on 320d/520d BMWs with N47 engines manufactured between 2007 and 2011. I wanted to know if models after March 2011 (when they supposedly changed the engine) have fixed this problem?

Also on this model, is the timing chain still at the back of the engine or the front?

Thanks

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HonestJohn says the timing chain is still at the back of the engine on this model and that "he" has heard of no reports post-2011 –  Sean Chapman Jul 17 at 10:52

2 Answers 2

First off, as said, the timing chain is still located at the back of the engine. The N47D20 is still being used today. I have not read anything about them changing out the engine, though there was this article from 2012 about BMW doubling down on their use of the chain at the rear of the engine, supposedly to go into production cars this year (2014), but I've not read where they've actually started using the engines. These newer engines are supposed to share many of the same components, have the same amount of displacement per cylinder (whether gas or diesel), and use the same mounting points in the engine bay. Even the HP ratings would be about equal per cylinder (though different between gas/diesel for obvious reasons). Until they do start utilizing the new engine, BMW continues to use the N47 as a mainstay in their fleet.

Since BMW will not own up to the timing chain problem (publicly), the best we can do is to see what the BMW owners community has said about it. According to the community, the problem lies with the crank shaft sprocket. This is an excerpt from this forum:

BMW recognized it as a fault and fixed the sprocket issue in roughly March 2008 (some older engines were still installed at a later date) but later model have since failed, the mechanics on the site have seen mainly jumped chains on manual cars that have been been ragged, auto's don't do the same harsh gear changes and so are less prone to failure.

Still, others claim the manual tranny v. automatic theory does not hold true. Failure rate does seem to have decreased dramatically since BMW made the changes, but that does not mean you won't have mechanical chain failure on the N47. Bottom line, if you start hearing the timing chain start rattling, you should get it looked at.

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Great answer. What are your thoughts on regular servicing (every 10k miles) preventing this problem? I've read in a few places that you should never have problems (even after 200k miles) with the timing chain if it's serviced every 10k miles for the lifetime of the car. –  Sean Chapman Jul 17 at 14:18
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@SeanChapman ... I'm not specifically a BMW guy, but I would highly recommend it. I think BMW's maintenance schedule is a little long for any car, but that's just my taste. Also, if you can afford it, I would highly recommend running full synthetic in the vehicle (flavor of your choice). This should help reduce friction in the engine and should help with longevity as well. –  Paulster2 Jul 17 at 14:27
    
No problem, thanks, this is all really helpful. Should I still run fully synthetic if it hasn't been ran with fully synthetic previously? (I haven't bought the car yet so I don't know) –  Sean Chapman Jul 17 at 14:32
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@SeanChapman ... That is up to you, but I avoid doing so. It seems that synthetic oil has a way of finding all of those little spots to leak out of on older engines. This may not hold true on every engine, but that's what I've seen. This is pure unsubstantiated conjecture on my part, so take it for what it's worth. Nothing to really back it up, except personal observation. If you get the timing chain done, I'd start using the synthetic from that point. Along with the reduced maintenance interval, the timing chain would probably last you forever then, but again, just my humble opinion. –  Paulster2 Jul 17 at 14:36
    
Okay I will keep all of this in mind thanks! I'm hoping to buy a used car with good service history and to never have to replace the timing chain as that would be almost half the cost of the car. –  Sean Chapman Jul 17 at 14:46

This is a very big job. The chains are at the rear of the engine, and requires engine, head, and sump removal to replace the chains. They engine is also set up with a set of special tools and timing plates. BMW say that any previous weaknesses are now resolved.

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Thanks for the answer, but resolved as of when? And do you have a link to a source? –  Sean Chapman Jul 17 at 11:09

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