Why are muffler bolts heated before you put wrench to them?

[vancouverbc]

Doesnt heating the bolt make it bigger? I thought you would heat the areat around the muffler bolt.

Hitting the bolt to break rust bond and allow the wd40 to penetrate faster makes sense.

[sommmatt]

lol wut

[bt2s14]

Heating it makes it more malleable...Made that up...

[ShopliftTHIS]

Anything colder will expand. Ever left a beer in the freezer? You get the idea. Metal is no exception.

[kane2g]

bull****cold - makes things smaller - think your balls being dipped in cold water

hot makes it expand - like that nice wet pus..... well you get the idea.

[vancouverbc]

thats a phase change. liquid to solid

[vancouverbc]

Heat and oilIf you have the time, several applications of penetrating oil over the course of a day or two can sometimes break a corrosion bond. Alternatively, repeatedly heating a bolt with a narrowly directed propane torch, then letting it cool, can cause the metal to expand and contract enough to break the hold. Direct heat to the fastener, not the material it’s threaded into, and try to work the bolt with a wrench during the process (wearing heavy gloves).

some people say heating the bolt makes it more likely that the bolt head will twist off. i guess if you wait for bolt to cool it is ok. use acetylene to heat it up fast so surrounding material does not have chance to get hot.

mapp gas might be good.

[Crazyirish]

Anything colder will expand. Ever left a beer in the freezer? You get the idea. Metal is no exception.

Only water exhibits this behaviour. (Yes there is water in beer. I know. I've done extensive research on the subject ) Everything else shrinks when cold.

[xckid]

in short and less writing to loosen up the bolts

[H8tred]

In my prior line of work (Working on dry van and reefer trailers.) I've found that nothing beats heat for removing a seized bolt/nut. What my employer did not understand, and I'm sure part of the reason I don't work there anymore, is that when you heat metal, and let it cool slowly, it weakens it. Ultimately, it is best to replace what ever it is that you're heating, and use a generous amount of anti seize before assembly.

When you get a bolt cherry hot, the outer layer almost acts as a lubricant, plus, it's just soft enough to get past anything it was getting caught on.

[murda-c]

Ice shrinks when cooled down too.

[VP4prez]

i work in a motor shop and the best way to get 99 percent of oil plugs out is to heat the block driectly around the bolt. but im sure this is the opposite because ur really just trying to smoke out all the gunk and road tar that has been there since the day the mani put the motor in. acetalene torch and a manual impact screwdriver, works like a charm

[PorkChopExpress]

bismuth also expands when cooled.

[Crazyirish]

Ice shrinks when cooled down too.

No It doesn't. Go back to high-school chemistry.

bismuth also expands when cooled.

Ok, yes bismuth, stable plutonium isotopes, and a couple of other elements DO expand when cooled, but those are rare exceptions.

[vancouverbc]

i think most solids get bigger as they increase in temperature. ice might be an exception but im not sure why.