How to cap brake lines

[blue62]

Originally Posted by JFP in PA

When you open the lines at the caliper, and then cap them, the air is trapped at the capped fitting and stays there. When the line is subsequently reconnected and then the system flushed, the air retained at the cap point is forced out of the system at the caliper bleeders.

If the line is not capped, that portion of the line system will slowly gravity drain all the way back up to the ABS pump and control network, getting air into an area that is difficult to get it out of without the diagnostic tool to cycle the valves and pump circuits while flushing the system. The air doesn't move up the system when it is full of fluid, the fluid drains out, letting the air in.

We regularly see cars that "have no brakes" or are throwing ABS/PSM codes after removing the calipers for one reason or another, during which time the lines were not capped. We hook up our Motive bleeder system, connect the diagnostic tool to cycle the ABS system, and a few min. later, the car can stop on a dime.

With the exception of using something like a motive bleeder system I do what you do.
Doesn't take very long and if the rest of the system is up to par I don't have any issues.