M635/M6 timing chain question

[JayM]

Does anyone who has had their timing chain done have pics of the upper guide? Called the "slide rail" it's p/n 11311306603 for the M88/3 and 11311308550 for the dual-row S38.

I ask because I got this answer from one source for parts (ECS Tuning):
"According to BMW, the part number you have gave is replaced by the number we gave. This is directly from BMW. If you want the part number you gave, we can not get it. We can only go off of what the BMW ETKA computer is telling us and it is saying that this is the replacement part number."

Now RealOEM, and Maximilian both show the M88 part as available (I haven't heard back from Max yet), and my local dealer has said it can be special ordered from Germany, but has to be manufactured on demand, hence the price ($707 CDN) and will likely take 6 weeks or more to get.

I doubt it has actually be superceded, and I'm sure a guide for a single-row chain must be different than that of a double-row, but to reassure myself I'd like, if possible, to see photos of both (I've seen the ETK diagramme). Failing that, if one of the guys that has done the job on both types, or done a single-to-double conversion can reassure me that I'm not smoking crack, I'd appreciate it.

[Layne]

I've still got my old one at home, I can get a picture for you. There is definitely a difference though, that's why the US one is like $100 and the euro is like $500. You shouldn't have to wait 6 weeks for it though.

[CW6er]

This may be of interest (S38): http://bigcoupe.com/phpBB2/viewtopic.php?t=155

PelicanParts.com lists part number 11311306603, as available on order from BMW for $443
(unless the 20% shipping charge from Germany applies- then $532)

BavAuto.com lists it at $433, call to varify part number and shipping

Interesting info on chains and guides: http://bigcoupe.com/phpBB2/viewtopic.php?t=8104&

[Bert Poliakoff]

I have had a lot of parts shipped in from Germany including the long fuel and brake lines that run under the body. My dealer has never charged me a 20% shipping fee

[JayM]

I checked Pelican and Max, but not BavAuto. It wouldn't surprise me that it takes 6 weeks or more if there is no stock on the shelves. The dealer I usually get from is pretty good about things like that, and it was mentioned as a warning - some other stuff he's ordered had to wait for a couple of months to be made, not just shipped off the shelf. That said, I'm sure there are some dealers out there who have one of these things sitting on a shelf, so I just have to find that one.

CW6er - I posted in that Big Coupe thread :D.

I've been researching this issue for a few years now. My conclusions:
The UK 100k mile "rule" is arbitrary. BMW and ///M have never issued a service interval for the whole timing chain assembly. That leads me to believe it's more a time issue, than one of miles. Plastic will degrade over time even if left alone in a dark room. Plastic that has been bathed in oil (possibly with lots of contaminants if regular servicing was not done) and suffering heat cycles will degrade more quickly, but ultimately it's time.

How long? I'm no engineer, so I couldn't say, but I'm reasonably certain that if it's over 20 years you're on borrowed time even if it's a 5k mile car.

If you redline it a lot, there are more issues and I'd say it needs to be changed more frequently.

Anyway, some posts here and elsewhere seem to indicate that if there's one part you can afford to skip when you do the refurb, it's the upper rail. I don't think I'll choose that option unless the part is unobtanium though. My main concern is to confirm that the S38 rail is not/not a substitute for the M88/3 one - though I think I have that confirmation through ASAP, which has no indication of supercession.

Now, where do I get one?

[Badgas]

I am in the process of having my timing chain, rails and tensioners replaced in my 85 M635. I cannot help you with the upper rail interchange, but I can say that after 23 years and 180,000 miles my guide rail was completely gone and the main tensioner was nearly cut in half by the chain.

I concur on age factororing into the servisability of internal plastic components. My feeling is that heat cycles would be the main influence. So lower millage city driving would reduce the life of these parts.

Based soley on my experience, my recomendation is to change all these components in the 160,000 to 170,000 range.