Carl Heideman
Carl Heideman
11/15/17 1:33 p.m.

Despite the often-shared advice about not buying rusty project cars, sooner or later you’re bound to encounter one. And those rusty cars are filled with rusty, crusty and cruddy fasteners–the kind that can rarely be loosened, even with chemicals.

There is another option, though: the hot wrench.

We’re not talking about a propane or MAPP torch. While these low-buck torches have their place, they typically can’t generate enough concentrated heat to deal with rusty fasteners. A full-blown oxygen/acetylene outfit is usually our tool of choice.

Conventional wisdom says that heat expands the fastener and helps it come off, but the reality is a little different. Yes, the fastener expands, but its mating part usually does as well, so that’s not much help. The key instead is to apply just enough heat upon exactly the right area–for example, to the nut but not the bolt–so expansion works in your favor. Meanwhile, heating up rusty fasteners can actually burn away most of the corrosion.

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dean1484
dean1484 MegaDork
11/15/17 4:17 p.m.

A rosebud torch is also very useful. 

RealMiniParker
RealMiniParker UberDork
11/15/17 4:44 p.m.

Streetwiseguy
Streetwiseguy UltimaDork
11/15/17 4:57 p.m.

I presume there is a paragraph in there somewhere about being very aware of where the rest of the fire is going...CV boots, brake hoses, ball joint boots...I've burned holes in all of these, and more.blush

ssswitch
ssswitch Dork
11/15/17 5:39 p.m.

In reply to Streetwiseguy :

The real lesson is in not immediately putting your hand on the metal surrounding the hot fastener.

Vigo
Vigo UltimaDork
11/15/17 9:07 p.m.

Regarding the 'only want to heat one of the mating parts' thing, i've actually had decent luck with ice cubes. Heat both parts, hit one with an ice cube (or any non-flammable spray that comes out cool/cold) and soak the heat out of it to shrink it while the other part is still hot. I also recently learned that when you heat a fastener that's inside of a larger/stronger part, the attempted heat expansion actually compresses the part somewhat and when it cools off it's slightly smaller in the constrained area than before you started. 

ChasH
ChasH New Reader
11/15/17 10:55 p.m.

I watched a co-worker using a blue tip wrench drop the object of his attention into the pocket of his shirt. He was a smoker so there was also a book of matches in there. 

There was much to be learned from that. 

NOHOME
NOHOME UltimaDork
11/16/17 12:20 p.m.

I get by using a plumbers rig, that being acetylene but no oxygen tank. Cant weld with it, but works fine for nuts and bolts.

 

RevRico
RevRico UltraDork
11/16/17 12:24 p.m.

I've become a big fan of using a candle with the torch.

Heat the parts up, touch the candle to the threads or end of the nut, wax goes into threads, bolt spins right out.

Kendall_Jones
Kendall_Jones HalfDork
11/16/17 12:38 p.m.
RevRico said:

I've become a big fan of using a candle with the torch.

Heat the parts up, touch the candle to the threads or end of the nut, wax goes into threads, bolt spins right out.

Likewise, but I quench with Kroil.  Spent a long time working on rusty cars in Detroit area, now spoiled in PNW.  I just did a tie rod change on my wifes minivan which was a rust belt car in the past.  Used propane, wrenches, cheater bars (completely unprepared) and half a sunday but got it done.

jimbbski
jimbbski Dork
11/16/17 1:34 p.m.

I have a friend who got his start as a auto mechanic at a Midias Muffler shop.  I saw him remove a rusted, broken flush stud in an exhaust manifold by heating the stud red hot with a cutting torch and then blowing out the stud with the O2. All the threads need was a quick clean up with a tap.  

 

AS for me while I have the torch, gauges, and hoses I don't have the tanks.  When I can access the nut on  a rusted nut/bolt assembly I try to use my nut splitter.

1988RedT2
1988RedT2 UltimaDork
11/16/17 4:14 p.m.
Streetwiseguy said:

I presume there is a paragraph in there somewhere about being very aware of where the rest of the fire is going...CV boots, brake hoses, ball joint boots...I've burned holes in all of these, and more.blush

LOL.  I happened to be channel-surfing last night and happened to catch an old episode of Big Bang Theory wherein the brainiacs unintentionally set an old van on fire trying to use heat to loosen a lug nut so they could change a flat. 

https://vignette.wikia.nocookie.net/bigbangtheory/images/3/3c/Burned_Van.jpg/revision/latest?cb=20151006211308

noddaz
noddaz UltraDork
11/29/20 8:15 p.m.

In reply to 1988RedT2 :

Funny on TV, not so funny in real life.  My BIL was using a torch to heat up and remove leaf spring bolts on his 1967 Mustang years ago.  It seems that he got the area around the front leaf spring eye hot enough to catch something under the back seat on fire.  Needless to say, the car was ruined.  Be careful with a torch, and then be more careful.

gearheadmb
gearheadmb SuperDork
11/29/20 10:06 p.m.

In reply to noddaz :

Same, I wish I could say it was an in law, but it was me. XJ Cherokee, using heat to to remove a leaf spring bolt. It worked, but after getting the bolt out I noticed a conspicuous amount of smoke coming out of the windows. Yep, the carpet was on fire. It wasn't even mine. It was a customers car. Luckily the customer was a dairy farmer that didn't really give a E36 M3, and the burnt carpet smell wasn't any worse than the cow E36 M3 it usually smelt like in there.

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