rchaas

I made a mistake and let the master cylinder run dry while flushing brakes (please don’t beat me up about it, i already have!). I refilled the master and thoroughly flushed using the motive bleeder, ensuring no bubbles at all the calipers. However, I did not bleed the master itself. Must one “bench bleed” the master or will a standard bleed suffice. The pedal travel is a bit long, but firm.

if a bench or vacuum bleed is needed, can someone describe the method?

DC911S

For some cars, you have to use a diagnostic tool to make the ABS system pump the brakes to finish off the job. I suppose that’s true for the 911 as well,

DR911s

If you don't have access to the electronic tools that will enable cycling of the ABS pump, you might try a technique I have used on several cars including BMWs and a 3rd generation Miata: reverse flow bleeding. Connect the fluid supply to the front left caliper bleed valve nipple [I'd choose the inward one on a Porsche or other vehicle that has fixed calipers with two bleed valve nipples], and push fresh new brake fluid from your Motive or other brand of pump device in reverse direction upward through the brake fluid lines and through the master cylinder into the reservoir.

This technique also works well for removing air bubbles that are trapped in a clutch slave or master cylinder after replacement of its fluid lines or either hydraulic cylinder, except that in such case, if both the brakes and clutch use a common fluid reservoir, you can do the job without an external source of pressurized brake fluid. Connect some plastic or rubber tubing to the left front brake bleed valve nipple and use the brake pedal to push fluid upward from the caliper through the slave cylinder and through the clutch master cylinder and into the reservoir. I've done this successfully on several vehicles where the owners struggled to regain hydraulic clutch function after installation of a new clutch slave or master cylinder.

rchaas

reverse flush sounds interesting, will consider.

rchaas

I do have an icarsoft unit that I think will allow abs cycling, fwiw

Zylinderkopfdichtung

I’ve done the same. I needed the iCarsoft (3.0 in my case) to do the ABS bleed. I was surprised by the bleed order that the iCarsoft required, but it produced a perfect, air-free result. I also got another can of fresh fluid and kept dumping the bled fluid back into the Motive bleeder and repeated the process a few times.

subshooter

No one is beating you up. Thank you for sharing this info. I learned something from this thread. Thank you for the help.

Ark20

I had a similar issue when replacing my calipers. Purchase the iCarsoft v3 since it has ABS flush functionality. Don’t waste time with v2. Although it advertised that it does ABS flush. It truly doesn’t. Make sure you have more than 1L of brake fluid. I would recommend having 2 just in case in your motive. Good luck!

Rapter

I just screwed up the same thing on my wife’s bmw…. Where the motive went dry and air entered the master.

to solve the issue… I bought 3L of brake fluid and did the following:

1. Lift up the right hand side of the vehicle with both front and rear tires off
2. Hook up pressure bleeder
3. Open both front and rear caliper bleed screws
4. With bleed screws open gently and smoothly pump brake pedal through the entire travel and hold for 5 seconds at the end of travel (all ports open when in this position)
5. 6-8 pumps per side
6. Repeat on left side

optional: repeat 🔂 procedure 2x . I had rock hard pedals after this.

Buy depressing the brake pedal all the way through the travel the user activates both the front callipers (the first portion of the stroke) and the user activates the rear callipers(the end of the stroke). In this way, you can eliminate all the air inside your system. Having the V3 pressure bleeder system and activating, the ABS is also a full proof way of sorting this out.

markk222

Did the same thing on my first bleed. Talked to a guy who races 911’s and he gave me a quick fix. Just hit an empty street and slam the brakes so that the abs triggers. Do it a few times and check fluid, problem solved.

DR911s

I intentionally get into the ABS system whenever I first drive on a track, for the reason stated above and to calibrate my brain as to the traction that is available. Of course, this needs to be done safely so as not to interfere with other drivers on the track. I've been doing this on a BMW that I tracked for 26 years and never had any issues with the master cylinder, ABS unit or the calipers. I did go through 3 sets of wheel bearings on the left side of the car and 2 sets on the right and several brake rotors. I also rebuilt some of the calipers as a safety precaution. I used ATE Type 200 brake fluid, and a machined aluminum cap adapter with an air compressor and a high quality precision air pressure regulator for fluid flushing. That air pressure regulator is the type that will bleed off pressure as the control **** is twisted counterclockwise to reduce the regulated pressure output; that enables me to totally eliminate the air pressure over the master cylinder reservoir before opening the cap. I have installed a quick disconnect in the threaded aperture in the center of the aluminum master cylinder cap.