[NathanM99]

Hi guys, doing a bit of research on the feared "timing chain" issue and according to this article " https://rightfootdown.com/automotive...nents-n26-too/ " they point out that if you check your timing chain part number on realoem.com Up to 01/2015 – then your part number would be 11317584084 and After 01/2015 – then your part number would be 11318648732.

Although interestingly enough, my car is manufactured on 5/14 and I have the updated timing chain part number? Take note that I am from Australia and therefore don't have a USA spec car, so would this mean that my timing chain is the updated version without the issues or not? If anyone more knowledge on this topic could shed some light that would be amazing, thanks guys

[Billfitz]

How do you know what chain you have?

[Slick_FThirty]

Interesting. Mine was as manufactured late 2012 (November I think), and when I use real OEM, it shows the latest timing chain part number.

Without a doubt, my car has the old chain, yet with my vin it shows the new one. I'm thinking it is showing the part number that should be used, and not the one I have.

[Slick_FThirty]

I just talked with the dealership (was really curious), and I have the supposedly updated timing chain part number. It matches what was shown on real OEM. Are you sure the part numbers shouldn't be swapped?

Need someone with a 2016 or 2017 to verify lol

Edit* okay, so other SA said it was just showing the latest part number. They said that they don't have the information about which specific part number is installed. If BMW does not have the capabilities to know, then Real OEM certainly wouldn't.

[Billfitz]

Originally Posted by Slick_FThirty

Mine was as manufactured late 2012 (November I think), and when I use real OEM, it shows the latest timing chain part number.

That's the part you'd use as a replacement, not the part that was originally installed. It can be confusing, as they show 11318648732 used as far back as 2004, but what they should be saying is that it's used as a replacement in cars made as far back as 2004. What's interesting is that the chain tensioner was superseded in 08/2016. They wouldn't do that without good reason. The tensioner is inexpensive and an easy DIY install, so I'd be inclined to change that pro-actively in any N20/26 engine produced before 08/2016.

[dave14x28]

so the timing chain changed p/n in 1/2015 and the tensioner in 8/2016...

anybody know when the 3 guides changed or what was done to make them better?

BTW I'm on the fence about changing the tensioner without upgrading the chain (and then the guides etc. since now you're in there).

I'll try to explain my reasoning - I bought the BMW chain elongation tool and compared it to a new tensioner, and also compared an old (2013) tensioner to the new one. According to the wear limit that the tool establishes, it appears that the difference between a new chain and a worn-out chain might be only 1/8" or 1/4" of chain length. Might sound like a lot but that's only a few thousandths of an inch per link. Also - the new tensioner has about twice the spring force of the prior one.

So... I don't know what they did with the chain design to make it "better", but if it had anything to do with wear resistance, I'd be reluctant to put a new tensioner on an old chain - it will keep the chain tighter, for sure, but it might accelerate the wear of the links and pins.

Bill's right, replacing the tensioner looks like a relatively easy DIY. So if you go that route, my advice would be to also buy the elongation tool from BMW and check it every 10k mi or every year or whatever makes you comfortable.

For my part, I've had the chain service done on my N20, but I'm also planning to check the chain elongation regularly. If I'm able to keep the car as long as I like to keep cars, I suspect that this new chain (and guides?) may need replacement again before it hits 200k mi.

Good luck!

in case you haven't seen this thread on the subject: https://f30.bimmerpost.com/forums/sh...614899&page=48

[dave14x28]

Originally Posted by Billfitz

How do you know what chain you have?

BTW I looked at my old chain (3/2013 prod date) and all I can see is what looks like a stylized logo that says "JWIS" (or "IWIS"?). Where the heck would they etch a big p/n like that anyway? So I think you just have to trust the data at REALOEM, no way to verify on the part itself that I can tell.

[Billfitz]

Originally Posted by dave14x28

it appears that the difference between a new chain and a worn-out chain might be only 1/8" or 1/4" of chain length... the new tensioner has about twice the spring force of the prior one.

I'd say that makes changing the tensioner a good idea, as it would do a better job of keeping the chain slop at a minimum.

[Slick_FThirty]

Originally Posted by Billfitz

I'd say that makes changing the tensioner a good idea, as it would do a better job of keeping the chain slop at a minimum.

Ya, FCP Euros video on the old timing chain had an elongation of 6mm relative to the new chain after something like 120k miles, which seems expectable and reasonable .

The new tensioner can extend more as well, is my understanding. On that basis, the elongation might not be as significant as long as the tensioner is doing its job well and accommodating for that elongation.

[Slick_FThirty]

Also, most failure occurrences that I have read about were a result of slack in the chain and jumping sprockets, and not the chain snapping (although I have read of that as well)

I still think changing the chain is good, but the new tensioner might do a good job in preventing slack.

[dave14x28]

Originally Posted by Billfitz

I'd say that makes changing the tensioner a good idea, as it would do a better job of keeping the chain slop at a minimum.

True, it's the lesser of the two problems for sure!

[dave14x28]

Originally Posted by Slick_FThirty

The new tensioner can extend more as well, is my understanding. On that basis, the elongation might not be as significant as long as the tensioner is doing its job well and accommodating for that elongation.

The tensioner immediately preceding the current one has the same lengths (both compressed and extended), actually except for a slightly raised "bump" on the face of the hex, you could mistake them for the same part! The tensioner before THAT, however, appears to have the same extended length (but longer compressed length) and also had a distinctly thicker hex head. I forget what model years that one covered. See photos below collected from other posts.

Hard to tell for sure from the 2nd photo due to lens distortion, but it's possible that as installed the tensioner with the thicker head doesn't protrude into the block as far, so it would not push the guide as far. I haven't seen one in person to be able to say for sure.

[Billfitz]

It would be interesting to see if there's a difference in the timing chain failure rates with the new chain and the old tensioner versus the new chain and the new tensioner. It might take Ethan Hunt and the IMF to find out.

[Slick_FThirty]

Originally Posted by dave14x28

The tensioner immediately preceding the current one has the same lengths (both compressed and extended), actually except for a slightly raised "bump" on the face of the hex, you could mistake them for the same part! The tensioner before THAT, however, appears to have the same extended length (but longer compressed length) and also had a distinctly thicker hex head. I forget what model years that one covered. See photos below collected from other posts.

Hard to tell for sure from the 2nd photo due to lens distortion, but it's possible that as installed the tensioner with the thicker head doesn't protrude into the block as far, so it would not push the guide as far. I haven't seen one in person to be able to say for sure.

Interesting. Thank you for the details.

My source for the info I posted was FCP Euro and one of their videos. But it seems like that should be a corrected statement then. Thanks.

[dave14x28]

Might depend on what year FCP was referring to? Dunno...

According to this source

https://www.bimmerfest.com/forums/at...6&d=1532363351

they switched away from the thick head and increased the travel in 2007, then in 2016 increased the spring preload.

I took the writer at his word, 'cause it seemed to be pretty well researched. But the dudes at FCP are pretty sharp too, so hard to say for sure where the discrepancy is coming from.

All I'm 100% certain of is how the current one compares to the early 2013 version that came out of my car, because I measured them both and tested their spring force out of curiosity.

[dave14x28]

also - if you're thinking of doing the tensioner DIY, know that there's a TSB SI B11 14 17 on the N20/N26 wastegate actuator linkage retaining clip that can get corroded in place and difficult or impossible to remove without breaking. There's a replacement retaining clip 83 30 2 456 269 that appears to be a better design. I think this may apply to the electronic wastegate actuator only.

The DIY instructions I linked to in the last post describe disconnecting the linkage at the actuator by loosening the outer nut without moving the inner nut - not sure if that's easy or hard in real life, haven't tried myself yet.

[dave14x28]

Originally Posted by Billfitz

It would be interesting to see if there's a difference in the timing chain failure rates with the new chain and the old tensioner versus the new chain and the new tensioner. It might take Ethan Hunt and the IMF to find out.

The models that would fall into the first category (new chain, "rev 1" tensioner) were produced between 1/2015 and 8/2016 are certainly old enough (60-90k mi) to start showing issues.

Interesting that it took another 1.5 years after the chain update to decide that the tensioner needed another update too. They must have done some accelerated lab testing to reach that conclusion, I can't imagine they got feedback from sold vehicles that soon after the chain update!

I doubt we'll ever hear much on how the various configurations fare over time (unless of course the aforementioned Mr. Hunt takes a personal interest to infiltrate das Mutterschiff).

[Slick_FThirty]

Originally Posted by dave14x28

The models that would fall into the first category (new chain, "rev 1" tensioner) were produced between 1/2015 and 8/2016 are certainly old enough (60-90k mi) to start showing issues.

Interesting that it took another 1.5 years after the chain update to decide that the tensioner needed another update too. They must have done some accelerated lab testing to reach that conclusion, I can't imagine they got feedback from sold vehicles that soon after the chain update!

I doubt we'll ever hear much on how the various configurations fare over time (unless of course the aforementioned Mr. Hunt takes a personal interest to infiltrate das Mutterschiff).

Ya, and BMW had 3 chains. The first chain was primarily for the 2012 models. Problems with this chain caused BMW to change the chain for the 2013 and up models supposedly. Then the chain was changed again, as we know around 03/2015.

2012 was the worst year for the TC problem according to my friendly parts guy at the dealer. Said they always had at least one 2012 N20 in for TC replacement at any given time. Probably sparked the revision to the chain for the subsequent years.

So for 2013/2014 and up, at least we have some kind of updated chain, although it's not the one we are after.

This 2013 chain is what people mix up as the chain that fixed the problem I think. People typically talk about 2 dates. 2013 and 2015. But 2013 wasn't the final fix, 2015 was.

[Billfitz]

Originally Posted by dave14x28

Interesting that it took another 1.5 years after the chain update to decide that the tensioner needed another update too.

That's the kind of thing that sets my engineering mind to wondering. My supposition is that they knew they had a chain failure problem, so they redesigned the chain, but not long after that realized that the tensioner was a problem as well and then they redesigned that.

[dave14x28]

Originally Posted by Billfitz

That's the kind of thing that sets my engineering mind to wondering. My supposition is that they knew they had a chain failure problem, so they redesigned the chain, but not long after that realized that the tensioner was a problem as well and then they redesigned that.

Me too. More questions than answers though...

[dave14x28]

My fear is that they knew all along that a stronger tensioner was one thing they could do, but it was the last resort due to the negative effect of more tension = increased chain and guide wear rates.

So worst case scenario, we now have a design which is more robust but does not last as long before requiring replacement. The lesser of two evils, yes, but what's the new service interval? Who knows... I'm just hoping the older cars figure it out before mine goes again!

[Billfitz]

Here's an interesting fact that doesn't seem to have been pointed out before: The N20 and N55 use the same timing chain. They have since 2004. They use the same slide rail as well. They don't use the same guide rails and tensioner. The N20 guide rail has not been changed since 2011. While the chain was superseded in 2015 it was superseded on both the N20 and N55 It may be more durable than the previous version, but since the N55 has used the same chain all along as the N20 and the N55 hasn't had timing chain problems I doubt that the chain is the problem, at least not in and of itself. The only component that would seem to check off all the boxes, not used in both the N20 and N55 and superseded after 2015, is the tensioner. The new tensioner is known to be different than the old tensioner. Putting two and two together to get four IMO the tensioner was the problem all along.