I am having problems getting the brakes to bleed on my big six. It has Boxster calipers, a 23mm master cylinder, and no proportioning valve. I can't seem to get a pedal. After about 3 pumps of the pedal, it comes up and there is decent pressure. But the minute you let off completely, it will go to the floor the next time the pedal is depressed. I have put over 2 liters of fluid through the system already, using both a power bleeder and Betty's right leg. Fluid is ATE Dot4 gold.


This is the same setup I ran on it for years. It has always had good pedal, no issues with bleeding it either.

Anyone got any suggestions on what might be wrong?

Bad seals in the master cylinder?
If it sat dry for a long time the seals may have got stiff.

You are using both bleed nipples (inner and outer) on the Boxster calipers I assume? Also - the rear brake lines have a "high spot" with standard pipe routing that just wants to trap air - even with no proportioning valve. Some creative angling of the car with jacks/axle stands can sometimes help when bleeding - good luck

- Tony

You bled the brakes for no other reason than to have fresh brake fluid or did you replace parts?

The master cylinder is new.




I had to remove the master cylinder to weld in a mount for the clutch master cylinder. Put a new master cylinder back in when I was done.

I completely forgot about the inner bleeders. That's how I can get rid of the air!!!


Now I feel really stupid!

Clay - make sure that fixes the issue before giving yourself a hard time!

- Tony

Put a tire valve on an old reservoir cap to make a pressure bleeder

I got it solved this morning. Bleeding BOTH bleeders on the calipers means I get all the air out of them. They work much better now.

And I am stupid....

Don't feel bad I did the same with my Brembo's...had exactly the same condition you have,mine came right straight away,besides that issue I have no other problems front or rear,good luck.

I'm another ignoramus. Did the same thing just a couple of days ago. Tried bleeding the brakes and got nice bubble free fluid coming out of each caliper.
Yet no brake pedal. Dang air in the system somewhere....either the master of the P/V I thought.

A friend stopped by yesterday and while I was showing him the car, he noted "you bleeding the brakes?"
Yeah, but I can't get a brake pedal.
So he helped me to quickly go through the procedure again.
When we got to the front brakes and I had bled the 1st side, he asked me if that was the inner or outer bleed valve?
Inner or outer? Oh boogers!
Yeah, these dang S calipers do have inner bleed valves don't they....
Son of a gun.

Long story short, both front inner bleed valves were holding back some air.
Once bled out, I finally had a firm brake pedal.

Sometimes you can't see the forest for the trees....or is it the other way around?