[mehrlovin]

I had the unfortunate accident of breaking a aluminum bolt while installing a stress bar on my E90. Any suggestions on how to remove this bolt? Should it be done with a bolt extractor or just drilled out with a smaller titanium drill bit?

[tcphoto]

I would try an extractor first and then try drilling it out if unsuccessful.

[IllSic_Design]

Yup, extractor/easy out if no then try a drill. Also, that's not an aluminum bolt in that spot.

[mehrlovin]

Oh interesting. I assumed it was aluminum but I guess not. I lubricated the bolt well but I guess it didnt want to budge.

[Efthreeoh]

Originally Posted by mehrlovin

Oh interesting. I assumed it was aluminum but I guess not. I lubricated the bolt well but I guess it didnt want to budge.

Okay, aluminum bolts are used on the E9X ONLY for specific applications for the N52 engine. The N52 engine uses a magnesium outer engine block. So any component that attaches to the magnesium engine block uses aluminum fasteners. The N52 cylinder head is aluminum, so steel fasteners are used on it. However, in the case of just the 2006 version of the N52, it uses a magnesium valve cover, so aluminum fasteners are used for the valve cover. The 2007 and up N52 use a plastic valve cover and use steel bolts.

Steel is very galvanically-reactive with magnesium, which is why it is not used for N52 engine block fasteners. All other fasteners on the E9X are steel. Steel bolts that look like aluminum have a dull, silver anti-corrosion coating.

When you say "lubricated well", do you mean you oiled the bolt threads, or used anti-sieze on the bolt. If you did, then that lowers the torque spec for that fastener. Looks like you over torqued the bolt.

[mehrlovin]

Interesting. I have a N51 and this bolt definitely looks aluminium to me. I applied penetrating oil on removal to free it, I don't recall anything being used on the way in. It may have been over torqued but not a whole lot. I have a fairly accurate torque wrench.

How much torque should you shave off if applying anti-seize or oil? Like 5lbs?

[e91Owner]

I find that a magnet is useful in reminding myself. Having removed the bolts you show in those photos many times myself, they are definitely steel with an anti-oxidation coating. Strangely enough, the aluminum bolts tend to look less like aluminum than the steel ones do as they are often shiny.

That being said, bolts of all kinds can be threaded into those holes. It may may have been replaced by someone incorrectly at some point.

[mehrlovin]

Originally Posted by e91Owner

I find that a magnet is useful in reminding myself. Having removed the bolts you show in those photos many times myself, they are definitely steel with an anti-oxidation coating. Strangely enough, the aluminum bolts tend to look less like aluminum than the steel ones do as they are often shiny.

That being said, bolts of all kinds can be threaded into those holes. It may may have been replaced by someone incorrectly at some point.

Guilty as charged! Do you know what the Torque spec is for this off hand?

[Efthreeoh]

Originally Posted by mehrlovin

Interesting. I have a N51 and this bolt definitely looks aluminium to me. I applied penetrating oil on removal to free it, I don't recall anything being used on the way in. It may have been over torqued but not a whole lot. I have a fairly accurate torque wrench.

How much torque should you shave off if applying anti-seize or oil? Like 5lbs?

While it seems simple, bolt torque is a complex subject. Torque values for bolts depend mostly on what type of bolt and what size of bolt is used. Type has a lot of variation related to thread shape, thread pitch (or count), class of fit, bolt material, and material strength to name a few. The determination of what bolt is used depends on the application it is being used for. BMW has a general torque spec chart for the bolts it uses in its products mostly based on size. Most torque specs are for "dry" applications where no oil or anti-seize is used. If an oil or anti-seize is used the torque spec is reduced by a percentage and not by a specific number. The type of thread used also has a lot to do with the torque spec because threads hold from the friction between the male and female thread faces. Any type of thread compound changes the coefficient of friction, and thread compounds affect different thread types differently, meaning if one reduces the torque spec for a course thread using an anti-seize compound say 8%, the reduction for a fine thread may be 12%.

But to talk in real terms, home mechanics get caught up in torque specs too seriously. Following torque specs for engine assembly are really important, as are wheel bolts (for safety reasons), but most of the applications in between, you can be close to the spec and it's good enough. Your car is not a spacecraft.

Too much torque is worse than too little. It takes practice to learn when the bolt is nearing the torque application spec by "feel", but you eventually learn it. And a lot of home mechanics do not use torque wrenches properly. Many use too big or too small of a wrench and use the wrong type of torque wrench for the application. Too big means the torque wrench is not accurate at the lower and upper limits of the wrench's capacity. Wrong type is beam vs. click. For example, you should only use a 3/8th-drive beam torque wrench on spark plugs.

[MightyMouseTech]

Originally Posted by mehrlovin

Interesting. I have a N51 and this bolt definitely looks aluminium to me. I applied penetrating oil on removal to free it, I don't recall anything being used on the way in. It may have been over torqued but not a whole lot. I have a fairly accurate torque wrench.

How much torque should you shave off if applying anti-seize or oil? Like 5lbs?

Pretty impossible to tell as it is a SINGLE USE bolt that gets a torque+angle. Never use anti seize. There is a reason why we don't even have that stuff in the dealer garage.

The fact it broke says yes, it was over torqued. Period.

[MightyMouseTech]

Originally Posted by Efthreeoh

While it seems simple, bolt torque is a complex subject. Torque values for bolts depend mostly on what type of bolt and what size of bolt is used. Type has a lot of variation related to thread shape, thread pitch (or count), class of fit, bolt material, and material strength to name a few. The determination of what bolt is used depends on the application it is being used for. BMW has a general torque spec chart for the bolts it uses in its products mostly based on size. Most torque specs are for "dry" applications where no oil or anti-seize is used. If an oil or anti-seize is used the torque spec is reduced by a percentage and not by a specific number. The type of thread used also has a lot to do with the torque spec because threads hold from the friction between the male and female thread faces. Any type of thread compound changes the coefficient of friction, and thread compounds affect different thread types differently, meaning if one reduces the torque spec for a course thread using an anti-seize compound say 8%, the reduction for a fine thread may be 12%.

But to talk in real terms, home mechanics get caught up in torque specs too seriously. Following torque specs for engine assembly are really important, as are wheel bolts (for safety reasons), but most of the applications in between, you can be close to the spec and it's good enough. Your car is not a spacecraft.

Too much torque is worse than too little. It takes practice to learn when the bolt is nearing the torque application spec by "feel", but you eventually learn it. And a lot of home mechanics do not use torque wrenches properly. Many use too big or too small of a wrench and use the wrong type of torque wrench for the application. Too big means the torque wrench is not accurate at the lower and upper limits of the wrench's capacity. Wrong type is beam vs. click. For example, you should only use a 3/8th-drive beam torque wrench on spark plugs.

It is torque to yield torque+angle. It is literally impossible to do that by "feel".

[Efthreeoh]

Originally Posted by MightyMouseTech

It is torque to yield torque+angle. It is literally impossible to do that by "feel".

Agreed for the tension strut bolt. 73 pd-ft +100 deg. But I was referring to bolts in general; not all are TTY.

[MightyMouseTech]

Originally Posted by Efthreeoh

Agreed for the tension strut bolt. 73 pd-ft +100 deg. But I was referring to bolts in general; not all are TTY.

Don't work on BMW much I guess.

[e91Owner]

Originally Posted by mehrlovin

Guilty as charged! Do you know what the Torque spec is for this off hand?

I think the posts above are quoting the torque specs for the bolt at the firewall. The bolt at the strut tower is the M10. If you tighten to 73 ft-lbs, you'll shear it again. Should be 40 Nm + 60*, or 30 ft-lbs + 60.

[mehrlovin]

Originally Posted by e91Owner

I think the posts above are quoting the torque specs for the bolt at the firewall. The bolt at the strut tower is the M10. If you tighten to 73 ft-lbs, you'll shear it again. Should be 40 Nm + 60*, or 30 ft-lbs + 60.

Great info thanks. Yeah 73 seems crazy, that would be a lug nut on the wheel. I will stick to 40NM.

I was able to remove it gently using a screw extractor and penetrating oil.