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      11-30-2012, 11:57 AM   #25
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Originally Posted by kimks View Post

I'm having the same exact problem. More often at cold starts. I know theyre not exactly connected to each other but i only started hearing the rattles just after i came back from the dealers. here's what happened to me.

i have 32k miles. 2011 lci e90 335i. Just recently, i started hearing it after i came back from the dealers with a faulty dmtl pump (got my car back 11/15). 2nd time this has happened in 3 weeks. the check engine light wouldnt turn off even after the first replacement. i ended up leaving my car at the shop for a whole week. The light doesn't come on anymore but i hear the rattle. (side note: my car is completely stock) so there's no way it could've been from mods.

Image removed from quote for space reasons...see previous post

Here's the tech report if it helps you in any way. I'm a bit concerned and it doesn't seem like they know what the problem is.

anyone else having dmtl pump problems? and possibly to rattles?
So you have the rattle/knocking noise from the engine bay, but no CEL? Here is what I know from the people and techs I've talked to. First let me start off by saying that my knocking/rattle sounds like a rock in a tin can and it happens at random. Sometimes it is very loud, sometimes it is very soft, and there is no rhythm to it. I also do not have an CEL or codes being thrown, so if you are similar situation, keep reading.

VANOS: The VANOS (Valvetronic System) deals with camshaft timing, and I believe that newer engines have a double Vanos. Single and Double VANOS systems due to age and mileage often experience performance issues as well as complete failure of the BMW OEM Buna-N VANOS piston seals (which are often successfully repaired by the use of aftermarket Viton seals to replace the OEM Buna-N seals). Another common effect is a rattling sound coming from the upper valve train assembly. The original seal material was found to be inferior for the application and tends to break down within 75k - 100k miles. VANOS Seal & Rattle kits are available to address these shortcomings from aftermarket suppliers (but not from BMWBMW's solution when VANOS units fail is to remove the entire VANOS unit and replace it with a new one). VANOS repair may require special tools (cooling fan clutch wrenches, etc.) that can be rented or purchased from a variety of vendors.

In addition to the rattling sound coming from the upper valve train assembly, you may experience CEL, engine codes, and I've heard from one source that your gas mileage can start to decrease. The source who told me this said their gas mileage went all the way to 7mpg before it failed. You may also experience white smoke from the tail pipes as the VANOS system continues to break down.

Solenoids: It is possible that you have a bad Exhaust Solenoids. There aren't as many cases of people experiencing the knocking, you would typically have a CEL light, but there are some instances in the N54 that the knocking occurred. The replacement of this part is much cheaper than replacing the entire VANOS system.

Rod Issue: Obviously this is the most extreme case, and the one that will suck most if you do not have a warranty. In this instance you either have a bent rod or a bad rod end bearing. A bent rod would make the knocking noise on a more rhythmic pattern, and it most likely speed up as you rev'ed the engine higher.

If it is the rod end bearing, it would cause the same symptoms the other two are causing and would increase in severity over time. The rod end bearing is a ball swivel at the end of the rod which something like a bolt or other hardware might pass through. With a bent rod you'll experience the knocking and at some point it is possible that you could throw the rod. The dealer said this is less likely to happen unless I were to do either an after market tune or a BMW Approved Performance Tune. If it is a rod end bearing then he said at any time that bearing could seize up and throw a rod. This would be the worst case because you're looking at your rod going right through the engine block.


For the VANOS you have two options. Obviously if you are under warranty just leave it with BMW. You may have to tell them to change the VANOS for you because they can be fickle about properly diagnosing the issue and replacing it. If you are not under warranty, the suggestion would be to get one of the after-market seal knocking kits and upgrading the VANOS. You can also purchase the VANOS and install that, but I think that is a more expensive route to take.

For Solenoids you can buy new solenoids and just replace those. On the N54 engine I've heard they are really simple to replace, but I haven't seen anyone on the forums who have done the N55 engine..may be due to the fact that N55's probably are still mainly under warranty.

When it comes to Solenoids or VANOS you are kind of stabbing in the dark unless you get lucky and your DME throws a CEL code. If you can get a code reading it should narrow down what the issue is and save you some time and money.

For the rod issue. This one is more difficult. First if you are under warranty, which I hope you are, you should make the dealer follow this course of action:

1) Replace VANOS and make sure noise is still there
2) Replace Solenoids and make sure noise is still there
3) It's the rod

What you're hoping for here is that you can get lucky that it is one of the first two, and not the third one. If it is the third one you're at least leaving the dealer with some new parts on the car that may end up failing eventually.

For the rod most likely your dealer is going to drop a new engine, send your old one off to BMWNA, and let them refurbish the engine. The reason why is because on an Inline 6 it is hard for them to do a compression/leak down test on each cylinder to determine which one has the bad rod. At the end of the day it doesn't cost them anything extra to just drop a new engine in and then send your old one off to BMWNA to let them hook it up to their more advanced machines and quickly find the bad cylinder. If you do have a bad rod this is good for you because you now hopefully have a new VANOS, a new Solenoid(s), and a new engine in the car.

One thing you want to make sure of is that the dealership doesn't replace the VANOS and give you the car back with the knocking noise still there. So make sure you start it up with the tech, let it idle, do whatever you need to do to be reasonably sure it was fixed so you aren't spending more time going back to the dealer when you realize they didn't solve the issue. Most dealerships shouldn't mind because their techs get paid by BMWNA to do this work, as opposed to the dealers having to pay them, so dealers love it when they can keep their techs busy with warranty work...especially if non-warranty business is real slow it means that they can let BMWNA pay their employees for them.

One final thing. You may note that we have eliminated the wastegate issue. The reason for this is because a bad wastegate gives what is called wastegate rattle. The rattle noise that this makes is very distinctive and differs from the knocking of a bad VANOS or rod. The engine specialist at the dealership should be able to tell you right away if the noise you are hearing is wastegate rattle. If not, then refer to the advice in this thread to hopefully help you get the issue solved.

Obviously there may be some other issue, but if you're car is having the same problem mine is having these are the 3 issues we've narrowed it down to. The car goes into the shop on Tuesday, so hopefully it won't be long after that I hear something back as to what is causing the issue 100%. I hate guess work.
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