Ron

I came across an article about needing a scan tool to bleed the brakes on cars equipped with ABS/ABD. It says as follows:

"On Porsche models with ABS/ABD a scan tool is needed to bleed the brakes. The scan tool bleeding procedure activates the return pump, intake valve and switch-over valve so brake fluid is supplied to the rear brake circuit in the master cylinder. The system is bled by opening the right rear caliper bleed screw, then turning on the ignition and selecting the bleeding procedure on the scan tool."

I have never heard this before. What's the story?

User 4621

I bled the brakes on my C4S with no problems using only a wrench.

Ron

Pete,

I bleed the brakes on my C2S with no problem either. So I'm puzzled. Is there another circuit that's not being bled?

Steve Weiner-Rennsport Systems

Hi Ron:

With all due respect to the gentleman who wrote that article (I've seen it), he is incorrect on this.

You do NOT need any scan tools to flush and bleed the brakes on Bosch ABS V equipped cars, unless you run the ABS controller dry and you must cycle the pump to bleed that device.

If the ABS pump needs replacement or bleeding, then you'll need the PST-2 or Hammer to do that.

Ron

Thanks Steve,

Hearing that from you is reassuring.

Greg Fishman

I have bleed my brakes dozens of times and I have only used that tool twice. Once when the master cylinder was replaced. The other was, well let's just say I pumped enough air into the system to fill a couple tires...

Derrick B.

My mechanic uses the scam tool every time. He used it to upgrade my HEPA filter to HEPB, for instance...


Sorry, couldn't resist!

Jeff96-993

Why would I not want to bleed the ABS system on the same schedule as the brakes? It seems that if there's a secondary system tied into the ABS then that fluid is still in a circuit with the primary one.

Am I only doing half the job that's needed by bleeding the primary system?

Steve Weiner-Rennsport Systems

Jeff:

When you bleed the brakes on these cars, you ARE pushing fresh fluid through the ABS controller, albeit at a slower rate.

Not to worry,...

JohnM

There is a separate procedure for bleeding the ABD (Automatic Brake Differential) circuit in the hydraulic unit on cars so equipped, detailed in the workshop manual. It says this should be done "when replacing the hydraulic unit or if the hydraulic unit has been removed". Brakes must be bled first and System Tester is required to do the ABD bleed. 4WD cars have an additional procedure for bleeding the brake booster circuit, only required if parts of the booster circuit have been opened.

Also worthy of note is that prior to October 1995 the reservoir has an overflow hose/bleeding hose which needs to be clamped off when using a pressure bleeder.


Would highly recommend getting hold of a copy of the workshop manual (if I was Ray I would include a "cheapskate" on the end of that, but I don't want to infringe his copyright )

Jeff96-993

John,

I'm working on the workshop manual even as we speak... I would have one already except the people who produce them don't seem to want to print any, at least at this time they don't want to print any. I'm on the waiting list.

Pete Lech

I managed to get air into my ABS system when flushing the fluid (duh) and was able to clear it without using the Hammer/scan tool. The procedure shared by another lister about bleeding the wheels in sequence and turning on the ignition to cycle the ABS pump after each wheel cylinder bleed did the trick. A pressure bleeder is the best, but my MityVac works and takes up a lot less space.