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- 2007.07 E92 M3 - Cold start knock - HELP!
2007.07 E92 M3 - Cold start knock - HELP!
I understand this is a german forum, but I have been dealing with this issue for over a month, and tried many things, and am out of ideas. Maybe someone who is closer to the mothership ( BMW @ Germany 
) can help. I do not speak german 
I am experiencing a multi-knock during cold starts. It lasts about 0.5 seconds, happens about 1 second after ignition takes place (so about 1.5-2 seconds after pressing start). The noise is quite fast so at first it sounds like a single noise, but I have recorded and examined the sound visually, and there is actually a sequence of knocks in succession (image attached below for reference).
Theres quite a bit of info as I have been trying to methodically deal with the issue as best I can.
Description of the issue:
a) The noise only happens on cold starts after the vehicle has sat for about 6 or more hours.
b) The noise only happens the first time the vehicle is started. In the following sense: START -> KNOCK -> OFF RIGHT AWAY (few seconds) -> START AGAIN -> NO NOISE....
c) Previous engine run cycle has an effect on it. In the following sense: If I cold start it now, get the knock, turn the vehicle off without actually driving anywhere (keeping the motor from heating up at all in essence), wait another 8 or so hours, start it again, the knock will be much quieter.
d) There are quite a number of people who are experiencing the same issue. Some say this is "normal". But many E92 M3's do not have this noise. I have talked to many people on m3post.com about this. Many people have this noise. Here is one example on youtube, this video is 4 years old, many years before I bought my M3 : https://www.youtube.com/watch?v=gvqsN7j0sYA <-- NOT MY CAR, someone elses car, same problem
Here is what I have done to attempt to resolve the issue:
1) Changed the check valves. Those that know this motor know there are 4 of them, one on each side of each head. They have been replaced. Cheap parts, expensive labor.
2) Tried adding oil.
3) Changed 2 vanos tensioners.
4) Remove starter, clean, grease. Starter in good condition.
5) I have installed a tune by bpmtune and had cold start deleted. So this is not related to the secondary air pump. Noise was / is present before and after the tune was installed.
6) I have removed my intake manifold and placed my head near the motor while my GF started the engine. The noise was there, very clearly, but due to the number (not necessarily volume) of noises coming up as the motor started... I could not determine where it was coming from. If I were to guess, and cant say this 100%, I would say somewhere from the drivers side valve cover.
Here are the videos / images that give quite a clear representation of what the issue is.
As always, any help is greatly appreciated.
PS: I know a noisy vanos is normal as oil fills back up. I am talking about the very obvious CLACK-CLACK. Some videos show it being better, one of them quite bad (longer, multiple clack-clack-clack...).
Videos:
Not so bad:
Worst:
Real Bad (someone on another form sudgested pumping the break prior to starting, the actual noise takes place around 0:49):
With intake manifold off:
Here is a wave form of the noise (from the really bad one):
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15 Antworten
What software level is the car running on?
DME is @ 240E.
Other modules are running old versions.
What sounds weird is, that pumping the breaks should have any impact on the sound. I would try starting to locate the noise using a stethoscope.
I have heard similar sounds coming from the ABS blocks on some (not BMW) cars, so the first thing would be doing a true location of where the sound is actually coming from.
i think this has to be the next step. very difficult tho, the noise happens one time every 6-8 hours, and to have my head under the hood, someone else has to start the car.
so its quite difficult to get myself under the hood to see where its coming from
Listening to the soundfiles my first assumption would be the starter.
But troubleshooting by that way is very hard.
yesterday we removed the starter, clean and greased it. the starter is in excellent condition.
Zitat:
Original geschrieben von brezelpaul1
Listening to the soundfiles my first assumption would be the starter.
But troubleshooting by that way is very hard.
Zitat:
Original geschrieben von anom3
yesterday we removed the starter, clean and greased it. the starter is in excellent condition.
Zitat:
Original geschrieben von anom3
Zitat:
Original geschrieben von brezelpaul1
Listening to the soundfiles my first assumption would be the starter.
But troubleshooting by that way is very hard.
So this could be excluded from the possibilities....
But as u are writing "we".... has there been not the possibility to listen more carefully to it?
Kann das jemand übersetzen?
same time we changed vanos chain tensioners. so it was difficult to isolate the noise because new tensioners had no oil inside so vanos was very loud for few seconds.
i will try my best to find out where the noise is coming from but its very difficult. happens 1-2 times per day (car has to sit 6-8 hours or no noise), also need friend / girlfriend to start car when i listen. difficult to align everything (wait for car to make noise, girlfriend home from work, etc etc etc).
Zitat:
Original geschrieben von brezelpaul1
Zitat:
Original geschrieben von anom3
yesterday we removed the starter, clean and greased it. the starter is in excellent condition.
Zitat:
Original geschrieben von brezelpaul1
Zitat:
Original geschrieben von anom3
So this could be excluded from the possibilities....
But as u are writing "we".... has there been not the possibility to listen more carefully to it?
I would thing rotating engine parts are rather unlikely. The pattern that the engine first starts clean, then makes the sound, then never does it again later, would be a very strange failure mode for something continuously rotating.
Maybe the Brake master Cylinder?
Have you already been to a BMW service point? They have no idea?
Zitat:
Original geschrieben von st328
Kann das jemand übersetzen?
Naja, hör dir die Soundfiles an, dann weißt ja was sein Problem ist.
Der Krach kommt nur wenn der Wagen vorher 6-8h gestanden hat, sprich beim zweiten Start kommt es nicht mehr. Das Geräusch ist schwer zu lokalisieren. Er hat bereits den Anlasser ausgebaut, gereinigt, neu gefettet und wiede rmiengebaut. Öl nachgefüllt und paar andere Dinge, aber hat alles nix geholfen.
Zitat:
Original geschrieben von Ritter_Chill
Zitat:
Original geschrieben von st328
Kann das jemand übersetzen?
Naja, hör dir die Soundfiles an, dann weißt ja was sein Problem ist.
Der Krach kommt nur wenn der Wagen vorher 6-8h gestanden hat, sprich beim zweiten Start kommt es nicht mehr. Das Geräusch ist schwer zu lokalisieren. Er hat bereits den Anlasser ausgebaut, gereinigt, neu gefettet und wiede rmiengebaut. Öl nachgefüllt und paar andere Dinge, aber hat alles nix geholfen.
Danke...hört sich ja echt grausam an
Hey guy, it is the starter. Its, not an specific M3 Problem, also other E90 have this problem. Your Local Dealer should know this.
The first Error occurrs mostly, if the Weather/Engine is cold.
I don´t know where are you from..... in Germany we have n Company called BOSCH-Dienst....there you can let your starter overhaul.
Here n example,i had found on youtube: