Light rust on steel tube / oil passages in crankcase

[stownsen914]

I had an aluminum SC case cleaned and checked a couple years ago, and then stored it in a bag in a cool, dry place. Forgot to oil the steel tube that's cast into the case, and now there's light rust in a few spots down inside where I can't easily reach. Perhaps soak with rust dissolving liquid, and clean with a pipe cleaner?

Recommendations appreciated for a good rust dissolving solution. How about POR-15?

[john walker's workshop]

Mole asses. 50/50 water.

[917_Langheck]

Originally Posted by john walker's workshop

Mole asses. 50/50 water.

I had no idea that a mole's ass was so rough.

Must be a pretty good trick getting it down such a small tube.

Evapo-Rust

[Dpmulvan]

Originally Posted by stownsen914

I had an aluminum SC case cleaned and checked a couple years ago, and then stored it in a bag in a cool, dry place. Forgot to oil the steel tube that's cast into the case, and now there's light rust in a few spots down inside where I can't easily reach. Perhaps soak with rust dissolving liquid, and clean with a pipe cleaner?

Recommendations appreciated for a good rust dissolving solution. How about POR-15?

I wouldn’t pour anything in there, tip engine upside down and use an engine block cleaning brush.

[stownsen914]

Thought I'd report back on this. Wound up trying a few different things.

First I tried engine cleaning brushes. They removed the loose rust, but left some visible rust.

I decided to try Evaporust. First I tried soaking a paper towel in it and stuffing it a couple inches into the tube. That did remove the rust, but it also left some black streaks that required further soaking with the Evapo to remove (denatured alcohol also seemed to work).

I also tried pouring the stuff in. This worked better on the rust, and no black streaks. I wanted to make sure I got all of the stuff out afterward, so I flushed with water since Evapo is water-based. I kept noticing the water coming out orange after soaking just a few minutes. I thought it was residual Evapo (which also is orange). Turns out it was flash rust forming! I didn't expect it so fast. I tried a fast flush with water followed by flushing with the denatured alcohol and then paint thinner. I still saw a little flash rust, grrr.

Around this time I happened to be at Harbor Freight and noticed a set of metal engine brushes, and figured why not. Much stiffer and more abrasive than the plastic bristled ones. A few plunges with one of those, and voila! Much cleaner overall on the rust, and it also removed a black coating deeper inside the tube that the other processes hadn't touched apparently. Squeaky clean now.
To avoid rust from reforming, I gave the tube a quick soak in a 50/50 mix of oil and paint thinner. Finally done!