Porsche 991: Flushing Brake Fluid (replacing)

This is my second blog post in a short series covering brake fluid service procedures for the Porsche 991 model line...

Checking Brake Fluid

Flushing Brake Fluid (replacing)

Bleeding Brake Fluid

All of the procedures I cover in this series follow the official Porsche NA Work Manuals, to which I provide reference with each post.

You don't need to take the wheels off, or jack-up the car...  BUT, getting to the inner bleeder valves will be very tricky and I would highly recommend removing the wheels.  In my case, I chose to get the car up on stands and remove all the wheels.  This way as I begin bleeding I can move from caliper to caliper without having to stop and remove each wheel along the way.  My own preference, YMMV and I am sure some are very content with other ways of doing a brake fluid flush....

So here is my car up on stands:

So let's get on with it!

If you are planning to replace the brake fluid in your 991, you should do the following....
1.  Place cover in service position.

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

Open Servic

2.  Open the cap on the reservoir, which is located on the driver-side under the service cover.
3.  Connect a bleeding device to the brake fluid reservoir.
4.  Switch on the bleeding device. Pressure when changing brake fluid should be ~ 2.0 bar (29 psi).

Connect Bleeding Device

NOTE:

• Check brake fluid quality. Use only new DOT 4 brake fluid. 
• Brake fluid can be ordered using the Porsche Electronic Parts Catalogue (PET). 
• There are two bleeder valves on each brake caliper. Brake fluid must be drained at both bleeder valves.   

NOTE:   The official WM from Porsche doesn't indicate any sequence or order to which (inner or outer) bleeder valve to start with -- just that you need to drain from BOTH.

5.  Continue to change the brake fluid at the brake calipers (no prescribed sequence, although some would suggest that you start at the farthest wheel from the master cylinder and work "towards" it...).

• 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.
• Drain brake fluid at both bleeder valves on each brake caliper. Per brake caliper: → Change brake fluid (on each wheel): approx. 250 cm3
• The shop manual doesn't indicate any amount of time to let bleed, or anything like that.  Just that you should capture the old fluid at each wheel, measure, and when all done replace with same amount (roughly).

6.  After fluid no longer flows tighten bleeder valves to the stipulated tightening torque and remove bleeder hoses. Tightening torque 14 Nm (10.5 ftlb.)

Move to next wheel.... and when done all 4,

7.  Switch off the bleeding device and remove the adapter at the reservoir.

• 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.

6. 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 470855 Changing brake fluid"