Clean enough?

Guys, I've been scrubbing and scrubbing the seal channels in my brake pistons with good results getting the old crap and brake fluid out, but there's some gray discoloration (likely due to the fact that it's unlikely the calipers have ever been cleaned in the 25 year history of the bike).

I've tried to post some pics here so you know what I'm talking about. I'm wondering if I should keep scrubbing (fine grade steel wool, toothpicks, Q-tips, mostly) until it's shiny aluminum again.

Both pics are of the same caliper, but all of them look similar.

Editor's note: my fingers are blistered from rubbing so I'm doing a cost-benefit analysis here on whether it's doing any good. The gray crap is pretty stubborn, so I just need some word from the pros whether I can get it off.

Thanks.

 

Hone that baby out will get rid of any scratches or pits

 

A Dremell tool with a brass or nylon brush will get rid of the spots in the seal grooves. If you don't have a Dremell a drill will work also. The cleaner the better, you are almost there.

 

"Discoloration" is one thing, if there's any "substance" to it at all, if it's still actual crud then it has to get gone. If the seals don't sit 100% perfectly "flat" withing the channels the piston will hang.

If you're planning to repaint the caliper, a little judicious use of heat from a propane torch will usually turn it to easily removable dust.

I too used my Dremel with a small brass brush to great effect. Sharpened shish-kebob skewers are great too, they hold an edge quite well.

 

After a second look I think the guy's have it right.
Dremel + bass or other "softer then alum" wire brush/wheel
will do the trick.
If no dremel avail, you might try 2000 or 3000 grit wet/dry with
a small edge tool to get inside the grooves.

That should be a last resort as even this fine a grit will leave conciderable
contaminates that need to be removed.

 

The most used tool in my house-slash-shop is a dremel, my advice is to get a nice one with variable speed to 30,000rpm as these little tools will last a long time if you replace the brushes on a regular basis

 

I use a dental pick to get all the crud out in the corners of the grooves. Works well for me on many occasions.

 

Once you have the Groove-channel all scraped-out to bare metal; you can see if there is anything you might have missed by wiping the Groove with a Q-Tip soaked with Lighter Fluid.

The Lighter Fluid will do a nice job cleaning the Groove and letting you see where you still have cleaning to do.

 

Ok, thanks for the tips. Latest development:
I was able to borrow a Dremel from a friend, but the brass brush is harder than aluminum and after a preliminary check, left a few scratches on the caliper body. I did try a nylon brush but that's definitely not working to remove the hardened, 25-year-old dirt, brake fluid, crap, that's bonded to the aluminum.

So, is brass ok to use on aluminum? I have this notion that it will start cutting away too much material, leaving the grooves unusable.

As a side note, I can't believe just how stubborn that old dirt, etc. is to remove. I don't think anyone's ever cleaned these brakes in the life of the bike, so that's literally 25 years worth of neglect I'm trying to do away with.

Advice welcomed. Thanks.