Porsche 991: Bleeding Brake System

And our last brake service post is a general how-to bleed the brake system on a Porsche 991....  If you missed 'em, there are two other guides available (all based on my experience with the official Porsche Work Manuals....).

Checking Brake Fluid

Flushing Brake Fluid (replacing)

Bleeding Brake Fluid

First, some important Notes:

• Observe brake fluid quality. 
• Use only new DOT 4 brake fluid. 
• This brake fluid is available under the following part numbers: Quantity supplied: 1 litre = 000.043.203.66; 30 litres = 000.043.203.67. 
• There are two bleeder valves on each brake caliper. Brake fluid must be drained at both bleeder valves. 
• Observe specified sequence: Bleed the outer bleeder valve on each caliper first.

1.  Place cover in service position.

• Unclip the cover at the left and right, lift it up and engage the yellow support in the luggage compartment lid ­1­ to secure it.

  

  Place protective cover in service position

2.  Open the cap on the brake fluid reservoir, which is located on drivers side of car.

3.  Connect a bleeding device to the brake fluid reservoir.

• Switch on the bleeding device. Bleeding pressure is approx. 2.0 bar.

  

  Connect a bleeding device to the brake fluid reservoir

3. Continue the following bleeding procedures at the brake calipers (no prescribed sequence, but note sequence of bleeding from outside valve first, then inside valve...).

• Use a transparent hose and a collecting bottle to check the escaping brake fluid for cleanliness, absence of air bubbles and to determine the amount of brake fluid used.  The Porsche manuals don't indicate any specific time for bleeding.
• Open each bleeder valve until clear, bubble-­free brake fluid emerges.
• NOTE:  Continuously pump the brake pedal slowly during the bleeding process (second mechanic required).

4.  Only when replacing the hydraulic unit: Bleed the secondary circuit using PIWIS Tester II 9818. Otherwise, continue with the concluding steps (Steps 5 and 6).

• Select >>PSM>>Maintenance/repairs>>Bleeding hydraulic unit<< in the control unit overview.  The four wheel brakes are bled alternately (as per Tester display).
• Remove vent hoses and tighten bleeder valves to 14 Nm (10.5 ftlb.).
• Remove PIWIS Tester II.

5.  Switch off the bleeding device and remove the adapter at the brake fluid reservoir.

6.  Visually check the brake fluid level.  The brake fluid level must be between the MIN and MAX markings.  Correct the brake fluid level if necessary.

Min / Max levels on fluid reservoir

7. Fit cover over the brake fluid reservoir (move out of service position).

The above details and illustrations are from the official Porsche Work Manuals for the 991 platform.

In this case the document you should obtain is "WM 470107 Bleeding the brake system"