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Technical Support / Re: C9 CAT t'stat housing frozen bolt
« Last post by Joel Ashley on Today at 01:40:26 AM »As Carl and Eric say, penetrant and vibration and heat are the go-to for these situations. I had a warped, noisy 454 exhaust manifold on our old Pace Arrow, some 35 years ago, and it took me weeks of crawling in and out of the wheel well to get the one stubborn bolt out. Ultimately it broke and I had to drill it out, an complicating circumstance I can't recommend. The ultimate loosening wasn't with heat, but with PB Blaster and many days of soaking, high-speed tapping/hammering, and cursing. If you can safely get at it, without igniting things or fluids nearby, heating the bolt head is worth trying, as I've used it successfully on other seized fasteners.
But the trick with penetrant and hammering is the vibration rate, in my opinion. Soak with penetrant and tap the head in a manner to vibrate the fluid into micro crevices along the thread path. It can take many, many sessions before the corrosion dissolves enough to succumb the bolt to removal stress. I never had an impact driver until recently, and am thinking the vibration set up by such a tool might help drive the fluid into the threads better than hammer tapping.
But certainly, heating to change the molecular nature of the bolt relative to the block is a great option.
Joel
But the trick with penetrant and hammering is the vibration rate, in my opinion. Soak with penetrant and tap the head in a manner to vibrate the fluid into micro crevices along the thread path. It can take many, many sessions before the corrosion dissolves enough to succumb the bolt to removal stress. I never had an impact driver until recently, and am thinking the vibration set up by such a tool might help drive the fluid into the threads better than hammer tapping.
But certainly, heating to change the molecular nature of the bolt relative to the block is a great option.
Joel