HELP: Broken subframe bolt in frame

[JGF30]

Need help removing rear subframe bolt.
Imaged attached and video linked
Image:
videos :

https://youtube.com/shorts/cwccQwroKBQ?feature=share

One of the rear subframe bolts has snapped and is stuck in the frame. Original mechanic tried to weld something to the bolt in an attempt to remove it but failed.

Brought the car into local BMW dealership and was told they cannot remove the bolt and was not given any recommendation on how to proceed. (see video for bmw explanation) Recently brought the car into another mechanic and they also said they cannot remove the bolt, however they did not attempt to. This mechanic told us we would likely have to have the section of the frame with the broken bolt cut out and replaced. They estimated this could cost $10k-$15k to do.

does anyone have any information or ideas about how to proceed with this. Cutting the frame and having the section replaced is not something we are willing to do. Looking for ideas or guidance on how to go about removing the rear subframe bolt from the frame.

[ellipsis212]

Why can’t it be drilled and then extracted?

[JGF30]

Originally Posted by ellipsis212

Why can’t it be drilled and then extracted?

That is what I do not understand. The last mechanic that looked at it seemed to believe it couldn't be. I was previously under the impression any bolt can be drilled out and re tapped.

Do you think the issue may just be finding the right shop/mechanic that is willing to drill it out?

[ellipsis212]

Access may be limited but also I think this is a liability they’d want to avoid because of the potential to mess up the chassis. A bolt can be drilled out though so you just need to find a willing participant and relieve them of any responsibility.

[robbo mcs]

I would contact a professional bolt extraction service. They almost certainly would be able to get it out. Problem then is whether it can be rethreaded.

[Tdog86]

It really looks mangled, I would have not drilled that far as now if you tried to weld something on it it has a greater chance it would snap but you could try to weld a smaller nut that would fit in the drilled hole then weld a bigger nut on top of the smaller nut. You could drill it out completely as stated above but are you sure the even drilled in the middle from the beginning, if not you risk messing up the threads and yes you can tap it but if it’s drilled off to the side, your risk the integrity of the clamping force and stripping it out. It’s a shitty situation, good luck.

[mikerunt]

Is it it worth to cut the subframe, get the bolt out then buy this and reinstall with a new / used subframe like this?

https://www.ebay.com/itm/28472233298...mis&media=COPY

I get that it’s a lot of labor removing everything from the current subframe, but could be an option.

[CrankhubF80]

Any updates on how you took off the bolt ? Just took off my rear subframe and my bolt snapped inside that hole

[JGF30]

Multiple shops could not remove the old broken off subframe bolt but eventually a shop was able to weld a bolt over the old broken sub frame bolt and to the subframe.

This bolt basically became a stud and was used to mount the subframe. The bolt has held up for months now and the alignment is fine.

[JGF30]

I am almost positive the reason no one would try to drill the old bolt out was because of the risk that too much is drilled and it not being able to be re threaded afterwards.

[Pic18]

So I just broke a subframe bolt on my F87 M2. I have an appointment at a shop later this week but have a question on how you got your car to a shop? Did you drive it or have it towed?

The shop I am going to is a 30 minute drive and I do not want to do more damage/bend the subframe by driving on it. That said I am also worried about towing it as I am unsure how a tow company would secure the rear of the vehicle?

[JGF30]

Drove the car for months with the broken sub frame bolt. It would make a slight clunking noise on hard acceleration.

Car was driven hard with the broken sub frame bolt multiple times with no real consequences, however every scenario is different.

[FaRKle!]

Originally Posted by Pic18

So I just broke a subframe bolt on my F87 M2. I have an appointment at a shop later this week but have a question on how you got your car to a shop? Did you drive it or have it towed?

The shop I am going to is a 30 minute drive and I do not want to do more damage/bend the subframe by driving on it. That said I am also worried about towing it as I am unsure how a tow company would secure the rear of the vehicle?

On my F31 I broke one of my front subframe bolts. No issue driving it for a day till the replacement came in since there were 5 other bolts holding it.

[Pic18]

Originally Posted by JGF30

Drove the car for months with the broken sub frame bolt. It would make a slight clunking noise on hard acceleration.

Car was driven hard with the broken sub frame bolt multiple times with no real consequences, however every scenario is different.

So looking at the photo you have the “nub” that comes down from the chassis (where the bolt goes into) seems to be bent up on your vehicle which is why I am concerned with driving it. Wondering if your continued driving the subframe was shifting and bent that “nub”? See the current status of my subframe below:

[Pic18]

Originally Posted by FaRKle!

On my F31 I broke one of my front subframe bolts. No issue driving it for a day till the replacement came in since there were 5 other bolts holding it.

Well this is the rear and there is only 3 bolts. It seems pretty solid but not sure how much it moves under load? Kinda like your video of the top of the rear shock mounts, worried it will bounce around and cause damage? That said whether driving or in a flatbed it is going to bounce around so just deciding what is the less of two evils.

[JGF30]

When the car was driven after the sub frame bolt broke you could feel the sub frame shift or bounce around when you would accelerate. This may have caused some marks and dents on the sub frame or the part it mounts to but it didn’t effect alignment or damage the frame.

If you are worried about driving it I would get the flat bed. The bouncing around on the flat bed will not cause any meaning full damage if any.

[Pic18]

Just wanted to give everyone an update as well as a possible PSA for F8X owners, especially those that drive in the winter (although water alone maybe the issue). The shop was able to get the broken bolt out after 5 hours of labor and a ton of heat, but it appears that the front bolts (on the rear subframe) are prone to extreme rust. After removing all 4 bolts the two fronts were completely rusted while the rear looked fine.

BMW maybe aware of this issue as they now use an updated bolt which has a washer with "cutouts". I am not an engineer but I assume the cutouts allow water to drain, reducing the risk of rust and seizing. It might be a good idea to upgrade to these new style bolts if you have any reason to lower your subframe.

[theweebabySeamus]

Originally Posted by Pic18

Just wanted to give everyone an update as well as a possible PSA for F8X owners, especially those that drive in the winter (although water alone maybe the issue). The shop was able to get the broken bolt out after 5 hours of labor and a ton of heat, but it appears that the front bolts (on the rear subframe) are prone to extreme rust. After rooming all 4 bolts the two fronts were completely rusted while the rear looked fine.

BMW maybe aware of this issue as they now use an updated bolt which has a washer with "cutouts". I am not an engineer but I assume the cutouts allow water to drain, reducing the risk of rust and seizing. It might be a good idea to upgrade to these new style bolts if you have any reason to lower your subframe.

Good info.

Also remember, the bolts are supposed to be replaced anytime they're removed anyways.

[andrewmr]

This reminds me of a situation a while back.

We were replacing a gearbox in a Cup car at the 24 hours of Daytona race and one of the mount bolts cross threaded. Boss said run it down tight and get the car back out on the track and we'll worry about the bolt next week.

If we were able to get that bolt out, you'll be able to get things like this thing out. And I see you wee able to... just posting for others not to give up on their efforts.

[Pic18]

Here is a link to the new bolt in which you can see the “cutout”:

updated bolt