Rick's Free Auto Repair Advice

Best way to loosen rusted bolts and screws

Here’s the best way to loosen rusted bolts and screws

How to I loosen rusted bolts and screws? I get this question all the time. And I see a lot of bad advice online. Let’s cut right to the basics. In order to free up a rusted fastener you have to get a penetrating fluid through the rust. That’s where most people screw up. Think of rust like paint around a ceiling light fixture in your house. If you want to remove the fixture, you’ve first got to cut through the paint.

Well, some rust penetrants can find small cracks in the rust and wick their way in where they dissolve more rust. But on a heavily rusted bolt, that’ll take a long time. Here’s a tip to crack the rust. Use a hammer or an air chisel with a hammer bit (shown below). Your goal is to set up enough vibrations to crack the rust. Then soak it with rust penetrant and repeat the vibrations. That almost always works. In fact, if you use the air chisel hammer I show below, I’ve seen screws and bolts vibrate themselves right out.

Rusted fasteners, rust penetrant

SG 91125 Air Chisel Hammer

If that doesn’t work, you’ll have to try heat. And this is another really misunderstood issue. Your goal is to shock the fastener, not destroy it. Everyone says to heat the bolt so it’s cherry red. Well, guess what? They’re wrong. You do that and you’ve destroyed the temper of the bolt and you MUST replace it. Repeat after me: The goal is to shock the bolt, not destroy it. So heat the bolt until it’s hot. Then shoot it with water to shock cool it. The expansion and contraction will break up the rust. Keep spraying until it cools. They shoot it with rust penetrant again.

Now let’s talk about rust penetrant. Everyone uses WD-40. WD-40 is a great lubricant and in some situations it can free up a rusty bolt. But it’s really just an all-purpose lubricant, not a rust penetrant. So my advice is to skip the WD-40 and buy a REAL rust penetrant like Liquid Wrench, PB Blaster, or FreezeOff. Next, understand that it takes at least 15-mins for

rust penetrant


a rust penetrant to work. Remember the paint scenario above? Well, paint stripper doesn’t work immediately and neither does rust penetrant. So soak it and walk away.

Here’s another trick. Instead of always trying to loosen the bolt, try tightening it. If it moves at all, resoak it with penetrant and alternate between tightening and loosening. That’ll work the penetrant into the threads.


© 2012 Rick Muscoplat


Posted on by Rick Muscoplat

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