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aioros
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I've been trying to remove the exhaust/muffler to replace the center support bearing from the drive shaft but it's stuck and it got rounded. I tried hot wrench it, spline and bolt remover to no avail. its the top passenger side one so there is little room. i changed the other 3 nuts and used spark plug anti seized.
any other ideas?

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TA
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Really about the only thing you can do at this point is drill out the stud and replace it. If you have a cutoff wheel and grinder, you can cut it off, but you will still need to drill out the remainder of the stud to replace it. As I recall, you need to use about a 7/16" drill. It's worth going out and buying a good quality metal cutting bit, it makes the job much easier. You then need to drill the remainder out with a 3/8" drill.

The replacement bolts that BMW sells are about $18 each. They are made of Inconel to help reduce the corrosion in the high heat & salt spray enviroment.
 

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plays well with others...
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If you can reach into that area with a dremel type tool and cut a slot down one side of the nut, striking the nut with a chisel will then split the nut. Depending on the width of the split you may still need to spray and/or heat afterwards. I believe the number for the nut is 18301737774.
 

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Actually you dont need to drill the stud cut the seized nut off and then using a hammer and punch drive it out then just us a good ole fashion nut and bolt when assembling with some anti-seize. I ended up doing two of mine fortunately I broke the nut off with the stud and just used a air hammer to blast the pressed in stud out of the exhaust manifold. Wait you dont need to remove the exhaust system to do the csb.
 

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If there is enough room to hammer in a socket. Use a torch to heat that nut until it's glowing, then hammer in a smaller 12 corner socket. Let it cool down and remove. Use antiseize and new fasteners to reassemble
 

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The next step would be cutting the nut off with a Dremel. A long and painful process. Then you will need to extract the knurled bolt (if that's what your car uses), which is just as much fun.

Are those nuts the correct copper nuts, or did someone replace them with regular steel ones from the hardware store? They look to me like steel in the pictures. If so, you know what you need to do before putting the exhaust back together.
 

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I have removed a great many rounded nuts with a chisel and hammer. The point is not to cut the nut off, but to catch the nut edge and start it turning off. It's hard to describe, but place a sharpened chisel with the flat tip parallel to the stud, and in a way that it will turn the nut CCW.
Heating it to red is a good idea and maybe can be turned with vise grips while hot.
Grinding with a dremel or cutoff tool along one side then turning with a chisel will often break the nut.
Another old technique is to weld a nut to the old one, but although it works really well usually, if it doesnt go right it makes a mess....
Id hold off on drilling to a last resort.


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I have removed a great many rounded nuts with a chisel and hammer. The point is not to cut the nut off, but to catch the nut edge and start it turning off. It's hard to describe, but place a sharpened chisel with the flat tip parallel to the stud, and in a way that it will turn the nut CCW.

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Cold chiseling, I have done this many times works great on hydraulic hose fittings especially when you use a air hammer.
 
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