Ask Kevin: What’s The Best Way to Loosen Stuck Bolts?

wrench with rusted nut Question: When trying to loosen a bolt that has been in been in place for years, is there any advantage to applying a quick high-torque force to it rather than doing it slowly? My experience has been that a sharp force may break things free whereas a slower application will sometimes cause the bolt to deform somewhere in the middle and eventually snap or twist apart. Thanks! Bob Coates Pinehurst, NC Answer: I haven’;t tried the method you describe—applying a sharp, sudden torque to a fastener that has been in place for years. I am interested to hear that it has worked for you. When I have tackled such things, I haven’;t had much information about what shape the fastener is in. Manifold bolts on car engines are a case in point; often, corrosion and heat have “waisted away” the shanks of such bolts, making them weak and likely to break off no matter what you do. But maybe there’;s the germ of an idea here. I once saw my uncle tap-tap-tapping on the manifold bolts of an ancient “Atomic 4” auxiliary engine that had probably last been serviced a generation before. He hunkered there, down in the bilge next to this boat engine, tapping on the fasteners. “What are you doing?” I asked. “Well, I figure these bolts aren’;t going to come loose unless I can break the rust that’;s holding them—they’ll just break instead. An old guy showed me that tapping on each one—good, solid taps—could eventually break the rust so you could then unscrew the bolt.” One by one, he got the bolts loose. In using this method, if there’;s limited room, a drift pin can transmit the hammer’;s impacts. Then there’;s the unending controversy over penetrating oils—each brand on the market has its True Believers. And there’;s the comparison test making the rounds on the Internet, purporting to show that the lubricant with the lowest break-away torque is a simple mixture of ATF dissolved in the solvent acetone. How could that be? The ATF is loaded with both extreme-pressure and oiliness additives. Thanks for sharing your experience with us. Send your “Ask Kevinquestions to We cannot guarantee a reply to every inquiry.

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