Instructables
Picture of Home-made penetrating oil
This weekend I did a front brake job on my vehicle.  After using 2 cans of commercial penetrating oil (lubricant) I still could not remove the rusted brake rotor from the axle spindle.   I had tried various additional things like a bigger hammer, heat and rapid cool, it would not come off.   Now this is not my idea, it took about 2 hours of internet browsing to find a solution and people who tried it were singing it's praises and now I am a believer also.   One person on another site said there was actually a study comparing this home-made to commercial brands and the home-made required 30% of the torque of commercial brands to loosen rusted bolts.   And it is by far cheaper than the commercial brands like WD-?? for example.

Here is what you need.  A cheap spray bottle (you probably have an empty one laying around).    In this bottle mix a 50/50 mix of 100% acetone and dextron/mercron automatic transmission fluid.    The two fluids will separate like oil and vinegar so you have to shake the bottle well before spraying.   

I mixed up a batch and let it soak for 15 minutes on the rotor and with a few taps it came right off.   Yesterday I spent 6 hours with 2 cans of the commercial brand with no success.   My other rotor was equally rusted, and came off the same with this stuff only.

Hopefully this helps someone else out too.
snotty1 year ago
Neat! I'll have to try that sometime.
Oh and don't go all the way around either because the weld might shrink and make it even tighter than it was before!
The trouble with something large like a brake rotor is that it has a huge thermal mass. You would need a big rosebud and oxy/acetylene setup to even make a dent in the thing. Next time you might want to try welding a bead around the hub with the biggest stick welder you can get your hands on turned all the way up. Probably use a deep penetrating rod like 6010 or 6011. I've gotten stuck axle nuts off this way. There is nothing like a welder to get a tremendous amount of heat into something VERY quickly. Induction heaters come close, but they are very expensive and don't have the pinpoint capability of a welder.

Oh yeah, and make sure you don't pass the current through the bearing!
MorNuN1 year ago
wikipedia shows the "guessed" formula as:

51% Stoddard solvent
25% liquefied petroleum gas (presumably as a propellant; carbon dioxide is now used instead to reduce WD-40's considerable flammability)
15+% mineral oil (light lubricating oil)
10-% inert ingredients

in fact, any lubricant you can dissolve in a petroleum solvent, just as kerosene or simply naphta could do.
blacckswan1 year ago
i liked this idea heaps however i didnt have any transmission oil and my funds were low so i used endine oil instead and it freed up my 4wd brake drums in just a few minutes . My father in aw had tried removing the brake drums for over an hour befor i tried this . bloody fantastic and thankyou for sharing your instructable . My friends are now using this as well
ki4oyh2 years ago
Sounds great. But, I would suggest some caution with the spray bottle. E.g., be sure that your bottle and/or spray apparatus, if plastic, are resistant to both acetone and ATF!
aaahotdog (author)  ki4oyh2 years ago
True. I would only mix up the amount you would use at a time. Since atf comes in plastic bottle, no trouble there and acetone is the main ingredient in nail polish remover, again a plastic bottle. I guess common sense is the rule here. I'd be more worried about someone using it around an open flame. Again common sense.
kretzlord2 years ago
absolutely awesome! I spent 2 days trying to get a rear strut out, this sounds like it would have made quick work of that