Low/high speed grinding sound

[Aidzer0]

Originally Posted by wpoll

Because drilling with right-hand drills just drives the broken bold in deeper... Using a left-hand drill helps the broken bolt un-thread... you might as well give yourself every advantage you can!

That’s a good point. Would it hurt if the bolt fell into the frame rail though? Because tightening the bolt it was loose but loosing the bolt it had a lot of resistance. Maybe if I use right hand bit it’ll just drive the bolt into the frame and drop in there?

I’m not sure if there are any drains or anything in the frame rail, that’s why I ask. Don’t need drains getting plugged and rusting the frame rail…

I will probably get left hand drill bits to be honest, but it’s an idea.

[Aidzer0]

This should be the last update on this thread, last night I finally assembled the car with all 6 subframe bolts.

Extracting the broken bolt was a steaming piles of a nightmare, it took roughly 8 - 12 hours of drilling, hammering and drilling again, a mate of mine and I were taking turns and he got the final blow to get the bolt out. Only broke one drill bit which was a surprise… but it finally gave up. I chased the threads on all 6 nuts in the frame to make sure. I put a tap through the mangled threads and a bolt fit in perfectly. For anyone wanting the front subframe bolt specs: M12x1.5mmx66mm galvanised steel. Apparently it’s tty but I have no actually written documentation to state that.

I used a normal hex head as a temp replacement, I’ve ordered 6 new subframe bolts just to be sure that this does not happen again.

Thanks to all for your input and knowledge, it’s very much appreciated.

[Henn28]

Ouch...sounds super painful. Glad it is done.

They are definitely TTY bolts. According to my Bentley manual stage one is 56 nm (41 ft-lbs) and stage two is +90 degrees. There are spirited threads on this and other boards about if you need to replace these bolts every time you drop the stiffener plate (they aren't cheap). I haven't replaced them yet but want to now that they have been on and off probably 4 or 5 times over the life of my car.

[Aidzer0]

Originally Posted by Henn28

Ouch...sounds super painful. Glad it is done.

They are definitely TTY bolts. According to my Bentley manual stage one is 56 nm (41 ft-lbs) and stage two is +90 degrees. There are spirited threads on this and other boards about if you need to replace these bolts every time you drop the stiffener plate (they aren't cheap). I haven't replaced them yet but want to now that they have been on and off probably 4 or 5 times over the life of my car.

Stiffener plate bolts are tty, I am referring to the subframe bolts, one of which I had to drill out. Some folks say they are tty but some say they aren’t.

However torque procedure is the same as stiffener plate bolts, if I recall, the subframe bolts are 100nm + 90° so that tells me that they are tty.
Regarding the stiffener plate bolts, yeah, I reckon mine are due to be changed too, but I’m sure that can wait for another day haha.

[Fifty150hs]

Originally Posted by Henn28

Ouch...sounds super painful. Glad it is done.

They are definitely TTY bolts. According to my Bentley manual stage one is 56 nm (41 ft-lbs) and stage two is +90 degrees. There are spirited threads on this and other boards about if you need to replace these bolts every time you drop the stiffener plate (they aren't cheap). I haven't replaced them yet but want to now that they have been on and off probably 4 or 5 times over the life of my car.

You can replace these bolts cheaply by buying the correct grade or better bolts from Belmetrics on line. I got six grade 10 bolts, nuts and washers for the price of one BMW bolt. They're not zinc plated, but they are cadmium plated.