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I have an exhaust tick that is noticeable when the engine is cold then diminishes once the engine warms up. There was an issue with exhaust manifolds cracking and/or mounting bolts breaking. The service manual states to use threadlocker GM 12345493 or equivalent on the bolt threads. Permatex high temperature threadlocker, red is equivalent and I believe Loctite 272 is an equivalent also but have not confirmed that.

With all the issues I've read about broken bolts, I am really nervous about using threadlocker on those bolts. I'm afraid if I ever had to do the job again, I'd never get the bolts out. I thought about using a nickel based anti seize compound on the new bolts but am concerned they may loosen up since GM recommends the threadlocker.

I plan to replace the bolts. The list price on the bolts is $5.99 each. There is nothing special about them - just M8x1.5x30mm washer head bolts in the 10.9 grade with a phosphate coating. Fastenal has them for a buck each...
 

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2004 Chevrolet Trailblazer 4.2L Inline 6 4WD LS
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  1. If you are worried, then do not use it. Torque the new bolts to factory recommended specification and well.... Send It!
 

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Discussion Starter #3
  1. If you are worried, then do not use it. Torque the new bolts to factory recommended specification and well.... Send It!
I used Loctite 272 high temperature red threadlocker per the GM shop manual. The original bolts had threadlocker on them from the factory. My 4.2l Exhaust manifold R&R thread outlines how I got them out without damaging the threaded holes in the head.
 
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