I'm preparing to replace brake fluids in my 914 and Cayman, and don't know how much fluid to buy?

1 can should suffice but get 2 just in case you knock one over.

Is the system already filled and braking normally (i.e. no air bubbles in the lines, just old fluid)?

If so, just a standard smallish bottle of DOT4 would probably be sufficient.

If the system was opened or drained then all bets are off and it really depends on your proficiency with the 914 system, specifically getting air out of the ABS system for the rear brakes (often mistakenly called a proportioning valve)

Systems are full now but old on the Cayman, and I'm replacing with DOT 3 for street driving. DOT 3 is suggested for more infrequent replacement, but found no info about what is recommended for either car such as DOT 4.

Hey BillJ, I see you also have a 2013 Cayenne diesel, my work horse!

ABS...Say wha?

Enlighten us please....

In theory a quart should be more than enough, but I'd get a quart and a pint, or two quarts. If it's cloudy, I like to keep purging it until the fluid is nice and clean, so it might take a little more.

For open systems / rebuilt calipers using a pressure bleeder, I usually need about two quarts. For just a flush on a currently running and good system, a pint or two.

Thanks y'all, my project for this weekend.

I just did this on my 912E and will do my 914 next, bought a qt of DOT3. Flushed out the old stuff and still have half a bottle left.

Enough if you screw up or spill it, right?

I just did this on my 912E and will do my 914 next, bought a qt of DOT3. Flushed out the old stuff and still have half a bottle left.

Enough if you screw up or spill it, right?

Likely in reference to this info on PMB's website.

Yeah love the diesel. Cayennes are just great and the torque on the 958D is very useable.