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A note to all E46 owners.

AvusHatesCones

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AvusHatesCones Newbie

AvusHatesCones

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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.

 

 

9346894512_02315c7a4d.jpg9344086755_a78ce0247e.jpg

 

9346867524_934efb901a.jpg9346890236_f9254c0636.jpg

 

9346884828_e48509c151.jpg9347023450_893f2dd21e.jpg

 

 

 

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.

 

 

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AvusHatesCones Newbie

AvusHatesCones

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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. 

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AvusHatesCones Newbie

AvusHatesCones

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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.

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jockhater2 Newbie

jockhater2

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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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REKIII Apprentice

REKIII

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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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AvusHatesCones Newbie

AvusHatesCones

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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

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Guest m3clubbmw

Guest m3clubbmw

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my guys does this kind of job he only charges 650$ and he works at a shop, so if anything goes bad you will get warranty but that will not happend they do it correctly to few other cars..

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Guest Whammy

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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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Guest bigjae1976

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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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AvusHatesCones Newbie

AvusHatesCones

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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.

That's not true, my subframe bushings were replaced at 65,000 as preventative maintenance and again now. They never went bad nor did they have enough time to do so. Also BMW never added the structural foam from the factory. The structural foam was only used as a fix for cars with 2cm or smaller cracks, the rest had the entire rear floor pan removed. There are only theories on what causes these floor pans to crack, no true facts on what it is.  

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Guest bigjae1976

Guest bigjae1976

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That's not true, my subframe bushings were replaced at 65,000 as preventative maintenance and again now. They never went bad nor did they have enough time to do so. Also BMW never added the structural foam from the factory. The structural foam was only used as a fix for cars with 2cm or smaller cracks, the rest had the entire rear floor pan removed. There are only theories on what causes these floor pans to crack, no true facts on what it is.  

So wait...you already had a crack then replaced the bushings and then didn't fix the crack at that time? Then you let the crack go for another 20k miles until this happened?

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Guest bigjae1976

Guest bigjae1976

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Yes, bushings can fail in 40k miles. Not unheard of. Especially if the diff mounts were on their way out. Usually if your subframe bushings are bad then your driveline mounts will be suspect.

 

I've went through motor mounts in my E46 330 (s/c'd) in a year. I had the powerflex rear subframe bushings which seemed to be fine after about 35k miles and 40 hours of track time.

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