Debris In Brake Lines

by John Grady

If you are working on your brake system and are not replacing the brake lines with new pieces, the old brake lines have to be thoroughly blown out. Likely there is dirt, rust, debris in there. Remove each line from the wheel cylinder and blow each line a few times with 100 PSI air and brake cleaner.

I have a suspicion that the inside of our brake tubes may not be coated or galvanized, or perhaps they are coated but whatever coating was in there has long deteriorated. This may be where the rust / crud forms.  Gylcol brake fluid will bring rust again, but it may take years. Silicone brake fluid will stop the rusting.

We recently did the brake system on a car and replaced all the wheel cylinders with new pieces. Imagine my disappointment when I discovered a leak from one of the new wheel cylinders. Looking deeper, I found debris in the new wheel cylinder which could only have come from the steel brake lines, which were the originals I re-used. Oh, I blew out the lines, but I didn’t do a good enough job and apparently when I bled the system, debris moved into the nice new wheel cylinders (!!). The debris does not come out of the line and into bleed bottle. It gets trapped in wheel cylinders, soon to be caught under the lip, causing a leak.