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, Fri, 19 Oct 2007 15:32:06
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Ancient though it is I'm going to chime in on this thread since it's a special interest of mine and something I have put a lot of time and earnest efforts into over the years.
No, I haven't heard of oil of wintergreen, maybe not a bad idea but in my experience almost ANYTHING makes a good penetrant of rust and crumbler of rust once you can get it into the rust. Most of the brand-name products are okay, some pretty good, but they're expensive, and lots of times they don't even touch the problem.
One of the better penetrants out there is a commodity, good old kerosene, but it's usually not in a convenient oil can and never in an aerosol with a little applicator wand.
Regular motor oil, and water, also work pretty well believe it or not.
Most of the car parts I see people on here posting about pre-applying multiple doses of PB Blaster or Rust-A-Dippity-Doo or whatever on, are so robust and tightened so well at the factory that any rust on them is superficial and hasn't made it far enough up the outer threads to matter. Plus they're so beefy that even if rust were part of the problem loosening them it's a small part and isn't worth worrying about.
Where rust IS a problem is on small stuff say 6 mm and some 8mm bolts, especially if the bolt comes through a nut and you can see rust on the threads on the back side.
Oil on those threads before loosening is a must with me.
And if it's a blind bolt but plainly having trouble coming out, maybe rusty, once I get it to move AT ALL I try to apply oil, or maybe an aerosol rust penetrant, to it just under the head, then re-tighten, loosen a little more, oil, tighten some, and do that back and forth repeatedly as I remove it, so the rust doesn't bind up and make the bolt break.
Also to do for removing nuts on rusty threads sometimes, even if you oil the bolt above the nut.
A am not worried about heating parts, other than burning things. Most car parts aren't heat-tempered and even if you anneal them some by heating them cherry red or orange even, if they're called on to do an important job they're made of steel good enough to take it. And if you quench them in penetrating the rust, that will temper them some but unlikely enough to embrittle anything much.
Heating, then applying kerosene, or motor oil, or even water, can work wonders as not only the heat cycling, expanding and contracting, lets the liquid get further into the part and breaks old physical-molecular bonds, but the quenching action actually breaks up the rust. It physically crumbles to fine powder instead of a hard thread-locking scale.
The easiest rust to deal with is on parts you can remove from the car before dismantling. Then if the metal isn't too massive you can heat them pretty well even with a propane torch, don't need acetylene, and quench in your choice of solvents, squirted-on oil, water or kerosene or something.
If you are heating a nut to get it off a bolt, and that loosens it and it's coming off nice and easy, then as you turn it it starts to tighten up, be careful. It was expanded by the heat but is cooling off and tightening. If it starts to squeak, stop right there and re-heat it and this time squirt some oil on it after you get it hot enough, or else keep re-heating it as it squeaks again. Rust on threads is locking it up and you could break the bolt even if you've gotten it to unscrew quite a ways.
A Snap-On salesman told tme a favorite trick of lobstermen and others on the waterfront, in removing broken studs say, is to give lots of heat, then melt a little candle wax (paraffin) onto the threads; though a solid it penetrates when hot and melted about as well as anything sold as rust penetrant. Then when cold the parts come right out, he said. I haven't tried this. Sounds pretty clean and not too smelly.
A big problem is with things like engine blocks, exhaust manifolds and brake calipers, they're too massive to be able to get enough heat into them to matter with anything short of an oxyacetylene torch. Good reason to own torches in the rust belt. Also, people good with torches don't bother with undoing things, they can burn a nut right off a stud, or a busted stud right out of a cast iron block. Or burn a garage down real easy tho, as noted above.
Thge biggest problem from rust is its space-filling properties, it locks threads right up. Corrosion, I guess lead oxide, does this too on battery terminal bolts. They usually will loosen okay but sometimes it makes people think their battery cables are tight when it's just the threads are locked up. Can remove it with a knife under running water, or on a wire-brush wheel on a grinder.
I have said on here repeatedly that threads should be considered like a wedge wrapped around in a spiral - - receptacle for wedge in the hole, wedge on the bolt. How do you loosen a wedge? A shock, driving it down away from the door or whatever it's holding.
So a real good way to loosen a tough bolt, rusted or not, is to shock it by driving it downward with a SMART blow from a hammer, sometimes a real big hammer. This pushes the bolt into the hole a little, drops its threads away from the threads in the hole, and gives it a momentary chance to break free. If you have a wrench on the bolt at the same time as you're hammering, and synch a strong push on the wrench with the hitting of your hammer blow, it usually pops free easily.
This works also on say phillips screws that are kind of chewed out, lock a vise grips onto the shaft of your screwdriver, hit the end of the screwdriver with a hammer just as you're pushing on the vise grips and you'll get it.
People regularly break off bleeder screws on brake calipers. Usually if they've been set a long time it isn't the rust so much as the metal-to-metal molecular bonding that keeps them from coming loose easily.
I like to give a hammer hit directly down on them before trying to loosen, which makes them a lot more likely to come out easy. And, the previous trick of synching hammer blow with loosening push with a wrench.
Bleeder screws are hollow and are made of mild steel so are very easy to break.
Also remember on bleeder screws, it's tempting to put a small box wrench on them. but most wrenches have a 15 degree offset on the box end (saves knuckles). Tthat offset makes it easy to apply not a straight circumferential push but also a neck-wringing angular twist that shears off bleeders.
If I'm in doubt I like to do my first bleeder loosening with a 6-point socket and 1/4 inch ratchet, to avoid the above.
Also, remove as much rust as you can and even lube with oil before reassembly of rusted fasteners. It makes it go lots faster despite the apparent time wasted lubing up.
Happy wrenching all...
posted by 71.241.192...
, Thu, 10 Oct 2002 08:46:43, Wed, 9 Oct 2002 15:29:21, Fri, 19 Oct 2007 15:32:06
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