Quote:
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.
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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.