Brake Bleeding

[WC13]

Earlier this week my brake fluid container cracked (long story). I replaced the part and did a complete fluid change. I believed I was done. For the heck of it I looked in the Bentley Manual to see if there was anything else I needed to do.... It says "Brake bleeding on vehicles equipped with ABS/TC 5.3 and PSM requires the PST 2 to activate the valves in the hydraulic unit for proper bleeding." Since my car has PSM I assume this is something that needs to happen.

Does anyone know why this is the case? What could/will happen if I don't have a PST 2 to complete the bleeding? Is Porsche the only place that has a PST 2 to complete this?

Additionally, if this is the case, wouldn't that make it rather impractical for people who like to change out their brake pads for track events?

Any assistance would be greatly appreciated!

Thanks!

[Loren]

:welcome:

Most dealers don't even hook up a PST2 (or PIWIS tester) when changing the brake fluid. Many good independent shops have a PST2 or PIWIS tester (PIWIS is a newer version).

A few of us have spent the several thousand dollars to have one too.

Common opinion is that you do not need to do that unless large amounts of air have gotten into the system.

I have a PST2 and I do not bleed the ABS every time.

[Richard Hamilton]

On my car, which has TC, the manual says to use the PST2 to bleed the ABD circuit after a fluid change, which it says is a separate circuit. Looking at the schematic for the brake circuit, it doesn't show a separate circuit, so it's a bit of a mystery to me. I do it all the same, just to be sure. I'm probably wasting my time, but its fun to control the pump with the PST2! ;)

Edited December 1, 2007 by Richard Hamilton

[WC13]

Common opinion is that you do not need to do that unless large amounts of air have gotten into the system.

I have a PST2 and I do not bleed the ABS every time.

Thanks for the welcome! I have checked with this site often and usually found someone else had the same questions I have. There is LOTS of great advice on this site!!!

Based upon the repair (replacing the fluid container) do you think that large amounts of air would have gotten into the system? Is there any way for me to tell? I did a complete fluid change, so there shouldn't be any air in the lines.

Additionally, I also noticed that the clutch uses the same fluid. How would I know if there was air in the clutch line?

Thanks for all your assistance!

[Loren]

Certainly air could be introduced if the pedal was moved during the tank replacement.

But, it is highly unlikely that air has gotten into the ABS system.

If you bleed the brakes as normally done I think you should be fine - you likely will want to bleed the clutch also as it is on the same circuit.

If you bleed the brakes and the pedal is squishy or soft then it is likely air in the system.

[Tool Pants]

If your brake pedel fells like normal then you should be ok.

At a work on cars day one of the guys wanted to bleed his brakes with a motive. I made sure he started the job correctly. Told him to watch the brake fluid level. Then I went to work on another car. Well, as he was almost done the motive went dry so he was forcing air through one of the brake lines. As a result he had no brake pedal - went to the floor.

So it was time to start all over. There was a PST2 there. I wondered if when we rebled the brakes if I needed to turn on the ABS because the motive had forced air through. Called I mechanic I know and he said no - just rebleed all 4 calipers. Mechanic said we might have to rebleed several times to get all the air out.

So we rebled and the brake pedal was back to normal. Did not use the PST2.

I have been told by the mechanics that you do not need a PST2 unless one of the components have been replaced, such as the ABS unit.