A note to all E46 owners.
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GET YOUR DAMN SUBFRAME INSPECTED!
My subframe went from one small crack to complete hell in 20,000 miles. Also when my car was checked at 60,000 miles it was completely fine so BMW did nothing to it. I know among E46 owners this issue has been beaten to death, but it really is a serious issue and it has to be reinforced, there is no way around it. If you don't have any cracks right now, great! Now go get it reinforced today! If I would have done even 1 track day as my car was before the repair, the floor pans more than likely would have been a total loss. And I dont know about you, but spending 6-7K on new floor plans sounds like one really shitty idea, versus less than a thousand on the reinforcement/repair. Your car will crack at some point! Just get this out of the way before it gets bad. The worst part is the lack of side effects, I only noticed a very minor cick on/off throttle in 1st gear, and the car still felt very confident at 8k rpm in 5th gear. (probably was not the brightest thing to do). All I'm saying is at least get it inspected, this will happen to every E46 (except possibly a very easily driven wagon, they had the strongest floor pans by quite a bit).
Now on to some pictures to scare the fear of god into you to get your car reinforced.
If anyone one is interested, I had the reinforcement/repair done by Jake at Rawsomotion. http://www.rawsomotion.com/
I have known Jake for a few years and referred many people his way , he does great work and will not let anything be done improperly. And he won't rip you off.
You may be a DIY person like myself, I almost never take my cars to a shop, but do not kid yourself. You're not going to do this repair without a lift and without being a talented in place welder, and you sure as hell are not doing that on your back under the car.
Silver Grey E46 M3
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Really? Jake does this work? That's pretty cool! Hopefully he gets to my transmission soon.
I'm sorry to hear about this. I had no idea the E46 body can crack. How is that possible?
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Wow, that got real bad real quick! Out of curiosity, how much did it cost to get it welded? That's quite a crack.
Typically its right around 1k to have it all done. That includes tearing apart the whole rear end of the car, chasing cracks, welding, and installing the reinforcement kit. Which in all honesty, isn't all that bad considering most shops charge near that just to swap out a clutch.
Silver Grey E46 M3
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Really? Jake does this work? That's pretty cool! Hopefully he gets to my transmission soon.
I'm sorry to hear about this. I had no idea the E46 body can crack. How is that possible?
Yep, Jake has become quite the fabricator. There are a few theories on what causes these cracks, I'm assuming its simply bad/too small of load points for the subframe mounts. This is know to happen on E36's also, just not to the same extent.
Silver Grey E46 M3
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Yep, Jake has become quite the fabricator. There are a few theories on what causes these cracks, I'm assuming its simply bad/too small of load points for the subframe mounts. This is know to happen on E36's also, just not to the same extent.
He started out working for my Dad when he was 19. I used to use jake ALL THE TIME. But now I do mostly everything on my own. Not the transmission though. F that.
Jake is actually really good at what he does guys. And his prices are very fair. Especially for those jobs that you look at and say...I can do that...but i don't want to.
Do you think that happened as a result of BMW trying to keep the weight down or something?
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Remember, the three seris is the most basic BMW. It's designed to be a 318 all the way up to an M3. The M3 USUALLY gets different subframes, but the attachment points are the same. The additional forces that the M's put on themselves is much more than a 318. These extra forces work on paper, but not after lots and lots of cycles.
The guys running HPF kits and whatnot much be tearing their cars apart.
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Remember, the three seris is the most basic BMW. It's designed to be a 318 all the way up to an M3. The M3 USUALLY gets different subframes, but the attachment points are the same. The additional forces that the M's put on themselves is much more than a 318. These extra forces work on paper, but not after lots and lots of cycles.
The guys running HPF kits and whatnot much be tearing their cars apart.
It's my understanding that this is just as common on 323/325/330's as well. It just snow balls once you get a little extra movement
Silver Grey E46 M3
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What year is your M? It's was my understanding that by the 2003, BMW had strengthed the subframes because of all the problems with the earlier years.
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What year is your M? It's was my understanding that by the 2003, BMW had strengthed the subframes because of all the problems with the earlier years.
Unfortunately, that's not the case at all. And mine is an 04. There are plenty of people with 06's that have the same issues.
Silver Grey E46 M3
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Wow.... I had only heard of that happening, but nothing that bad. I had my 330i looked at and luckily never looked that bad!
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^ Yep, some worse than others, but the worst one ever I saw (other than 800+hp M3's) was a stock 323i so it can happen to any E46.
Silver Grey E46 M3
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OP, not all E46s are affected by this change. Pre-facelift BMWs 99-01 were mostly affected by the change, in early 2002 (not sure exactly when), BMW corrected the design flaw in the body/subframe.
It is definitely a concern for all e46s but truth be told, not all have been affected. I have yet to see one facelifted E46 affected by the subframe cracking issue the pre-facelifted E46s have.
Edit: If you want more details on this, pop over to forum.e46fanatics.com
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BMW also "corrected" the the M3 in 05 and 06, and those fail just as often as well. They never actually fixed anything.
Silver Grey E46 M3
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What kind of symptoms did your car have when it started coming apart?
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Just a click sound off the line and when entering very hard left hand turns. As well as slight mid corner tracking from the rear, but only enough that only I'd notice occasionally.
Silver Grey E46 M3
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The subframe failure is the result of bad subframe bushings. The rear subframe is secured to the floor pan with 4 studs which are screwed in. What happens is the 4 subframe bushings go bad (typically the fronts) and then allows the rear subframe to twist everytime you accelerate and decelerate. This twisting loads and unloads the force of the subframe onto those studs which in turns leads to the metal fatiguing and cracking. Then continued use will result in your rear floor basically tearing itself out of the car.
First, address your driveline bushings. Typically motor and diff mounts fail quickly and are the first to go. Keeping the engine, tranny, and diff mounts, guibo, and center bearing in good shape will reduce the stress on your rear subframe bushings.
2004 BMW started using structural foam in the rear floor which helped.
The problem is there's no way to really see if the rear subframe bushings (that I know of) have failed. Most won't do preventive replacement due to the cost.
IMO, the fix is preventively reinforcing the 6 mounting points and installing solid rear subframe bushings. The solids won't add much NHV and will last a lot longer.
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