Any good info on the best way to do a brake flush, specifically on a BMW?
There's not a ton of info on this website about brake flushes.
What is the best method of flushing the old fluid out?
Power bleeder? 2 person method with pumping brakes?
Do I need to use a scan tool / INPA for anything?
Fluid wise, I was planning on using 2 quarts of this Pentosin DOT 4 LV
DOT 4 LV Brake Fluid (1 Liter) - Pentosin 1224116
www.fcpeuro.com
My response will be similar to the TC and trans threads. Use ISTA (or any diagnostic tool which can activate the mode), run the brake bleed program, follow instructions. While I had non-BMWs or E series cars, I did the two person old school method. Since getting an F series I've gone to the factory procedure, don't regret it, and will evangelize it (and somewhat wish I had switched earlier on my E90 which had DSC III)
It still calls for two people, one to pulse the brake pedal, one to open and close bleeders and tell ISTA to advance to the next step. 2L of brake fluid is required, so is a power bleeder. It calls for DOT4LV so you're right on target with that. I got the Motiv bleeder from ECS or FCP (forget which).
The only place I diverge from the official instructions: the instructions say to repeatedly depress the brake pedal
to the floor. With an 11 year old car, I put a brick or chunk of wood under the brake pedal so it stays in the normal range. This is a more old school way to keep the brake cylinder from travelling into "unused" territory and damaging the master cylinder seal on any rough patches of the cylinder bore, requiring replacement of the master cylinder. I don't need that kind of crap as the unintended consequence of good maintenance.
The factory brake bleed program on my F10 does FAR more than just "run the pump". In one 20 second burst it moves the entire volume of brake fluid out the bleeder (instead of 5 minutes of pump, release). Then it proceeds to run through a variety of actuator and pump exercises for the DSC. Machine guns, rattling, buzzing, high frequency, low frequency, followed by a final perfect bleed. (This is why 2L is required, perhaps buy 3 for your first time just in case you go through more fluid).
I have read accounts online for F series vehicles where experienced DIYer owners doing old school end up with soft pedals until they do it the ISTA way and it's rock hard.
For what it's worth - my F10 doesn't do a lot of miles. It's a 2011 and only up to 60k miles. When I change the brake fluid every ~2 years, I feel an improvement in performance - firmer pedal, brake torque increases faster in correlation to pedal pressure. When bleeding I usually tend to get some fluid out at the beginning that seems thicker than new fluid, especially at the rear. I feel like I've only noticed this since having a car requiring LV fluid, but cannot swear to it in court. I write this to communicate that the ISTA process works well, and even at a low mile moderate interval like 2 years I can feel improvement so I would look to shorten the interval if anything, not extend it.