I'm installing a new front brake line on my bike, and I was wondering if I should use some kind of thread locker on the banjo bolt to line connections. It seems like it would be a good idea to use loctite 242 on there.
Yup, I agree. Take a close look at that banjo bolt. If you "picture" how it works you'll see that loctite would seep into the channel where the brake fluid lives when you tighten to the bolt. That's a bad thing.
And now, for something completely different.....
Ok, so on the subject of washers and banjo fittings, I know to use two washers where a banjo bolt mates to a banjo fitting (one on each side of the banjo fitting), but what about where the brake line screws onto the banjo fitting? Should I use a washer there too? If so, what size? 10mm?
I can't picture any place where a washer would be appropriate if you're making your own brake line. I guess it depends on your particular setup, but I'd say no. I'm kind of lazy and buy the premade ones though so I'm no expert on the issue.