How to cap brake lines

[blue62]

Originally Posted by s_wilwerding

> You should be able to fill and bleed a completely dry system with 1-1.5 bottles of fluid.

I don't mind doing that - just wondering if there are adverse effects - I've never purposely filled my lines with air. Any issue with having to also bleed the ABS/PSM?

I don't see any issues....
When you remove the calipers your going to introduce air into the system no matter how fast you cap off the lines. No way to control where that air migrates to.
If you have a OBDII scanner with a Porsche Program it makes it a little easier as you can activate the ABS/PSM with the scanner.
But I have never had any issues bleeding any type of system on any car.

Perhaps if I am missing something JFP in PA will jump in and clue us both in.

[s_wilwerding]

Originally Posted by blue62

I don't see any issues....
When you remove the calipers your going to introduce air into the system no matter how fast you cap off the lines.

Since the calipers are lower than the brake reservoir, removing the calipers does not introduce air into the system - that's why the fluid is leaking out. Yes, when you put the calipers back on, they will be full of air that will need to be purged, but in no part of the process should air be getting sucked back into the system.

[blue62]

Originally Posted by s_wilwerding

Since the calipers are lower than the brake reservoir, removing the calipers does not introduce air into the system - that's why the fluid is leaking out. Yes, when you put the calipers back on, they will be full of air that will need to be purged, but in no part of the process should air be getting sucked back into the system.

Your car do it your way

[JFP in PA]

Originally Posted by blue62

I don't see any issues....
When you remove the calipers your going to introduce air into the system no matter how fast you cap off the lines. No way to control where that air migrates to.
If you have a OBDII scanner with a Porsche Program it makes it a little easier as you can activate the ABS/PSM with the scanner.
But I have never had any issues bleeding any type of system on any car.

Perhaps if I am missing something JFP in PA will jump in and clue us both in.

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.

[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.

[JFP in PA]

Originally Posted by blue62

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.

If you do it quickly, and the lines are not left open for very long, it is not an issue. But if they are left open for a prolonged period, they will drain, and there will be potential problems.