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I was changing the Exhaust Manifold on an '09 Chevy Malibu. When tightening the bolt with the new one on, I twisted the whole bolt and stud off. So I have a couple issues. The broken stud is now left on the back of my engine.

What should I do to fix this? Options considered: Remove the broken stud. If so how? Weld a nut, drill it out, etc. Leave it? There are 9 other bolts. Is that good enough to form a seal with 1 missing? Currently, it still leaks exhaust.

Another question here: Question2.

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    Picture of broken stud would be nice, ever situation is different – Moab Jul 29 '16 at 21:47
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You should definitely try to extract it.

Preparation:

  • Heat the manifold with a blowtorch
  • Jolt the bolt with a pin punch
  • Soak the bolt with bp-blaster or another penetrating oil

Removal

  • If the bolt is protruding: Place two nuts on it, counter them against each other and try to screw the bolt out.
  • If the bolt is protruding but not enough for the two nuts: Grind a small groove in the bolt, use a punch to hammer tangentially into the groove thereby causing the bolt to rotate counterclockwise.
  • Drill the bolt out. If you damage the threads: Drill the hole larger and use a "time-sert" or "ensat" thread insert.
  • This solution also exists, but it is dangerous: Drill a hole into the bolt. Then hammer a torx bit into it and try to remove the bolt. Attention: If the bit breaks your bolt is filled with a hardened steel inlay, not allowing a second chance.
  • The best method: Buy a screw extractor set, including a left cutting drill bit

Installing the manifold

To prevent other seized bolts: Be sure to use some anti-seize (cooper or ceramic paste) on the bolts. Attention: The recommended torque is for a dry bolt unless the instructions tell you to lubricate the parts.

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    Small correction. The recommended torque is for a dry bolt unless the instructions tell you to lubricate the parts. – dlu Jul 29 '16 at 22:02
  • I posted what actually worked in my situation below, but I'm giving you the answer, since I think it will be more useful to others coming here in the future. – Dylan Cross Aug 11 '16 at 13:29
  • I'll also add. Use a torque wrench when reinstalling the manifold. The bolts are a beast to remove, but require a surprisingly low amount of torque to spec. If you don't have a torque wrench, make them snug, but don't put all your strength into it. – Dylan Cross Aug 11 '16 at 13:31
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After a lot of research, I decided to start by trying a pair of vice-grips on what was left of the stud. I cranked them down real tight, and it came right out.

If that didn't work I'd have been going down the route of drilling, welding, or other more terrible options.

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