Stubborn bottom bracket threads got me to try something I swore I'd never do

Had a steel frame come in with a bottom bracket that was basically welded in by corrosion. Customer said it hadn't been touched in maybe 15 years. Tried the big wrench, heat, penetrating oil for a week, the whole song and dance. Nothing. I was about to tell them it was a lost cause. Then I remembered an old timer at a swap meet in Cleveland saying he'd used a mix of automatic transmission fluid and acetone as a penetrant. Sounded like junk science, but I was out of ideas. Mixed up a 50/50 batch, soaked it for two days, and it came out with just a steady pull on the wrench. I still think it's a weird trick, but it saved a frame. Anyone have a different last-ditch solution for seized threads that actually works?

4 comments

4 Comments

the_jennifer2mo ago

But what if the magic juice is the only thing that buys you that waiting time in the first place?

max_torres442mo ago

Tell the_jennifer the magic juice is just expensive patience in a bottle. Sounds like we're all just paying to not wait.

violar3527d ago

A week is overkill unless you're dealing with rusted solid. Kerosene works fine but the soak time depends on the temperature. Warm it up to 100 degrees and the capillary action does its thing in 12 hours, not a week. The putty dam trick is good for keeping it contained, but foil tape leaks if the surface isn't perfectly clean. Use a small hose and a funnel so you can top it off without pulling the seal. The real key is getting the fluid to the backside of the seized parts, not just the first threads.

violaramirez2mo ago

Honestly, the real trick is the soak time. People give up after a few hours. That ATF mix needs days to creep into the corrosion. I've had the same success just using plain old kerosene, but you have to seal it in. Pack a putty dam around the shell, fill it with fluid, and cap it with foil tape to stop evaporation. Let it sit for a week. It's always the waiting game that works, not the magic juice.