[KnighTT]

So, long story short. I took off my calipers, painted them, upgraded the rotors, upgraded all of the brake lines, upgraded suspension, and put everything back in.

I went through the entire brake bleed process in INPA.
Afterwards, when I went to start up the car and test drove, I got a DSC error. When you go to start the car, as soon as the ignition fires up, the brake pedal goes to the floor.
So I inspected all of the lines. I went through the bleed process in ISTA. Same outcome.
I went through the process in INPA again. Same result.
Two messages/codes I get is air in the system and air in the system rear left. 005DA7 and 005DBD.
I've now bled it 4 times.

When the car is off, the brake pedal seems to have the right brake pedal pressure. As soon as you start the car, the pedal will just go all the way to the floor.

No error about the pump. The DSC module seems to do all of the powered bleeding procedures just fine. Feels strong.

I have no idea where to go from here.

[KnighTT]

I guess I'm going to keep hammering away on bleeding the rear left. No one has any advice and I have found basically nothing across the interwebs on this.

[Suvorovo]

Lots of questions. Did you bleed the system first with a pressure bleeder before activating the DSC pump? Did you attach the pressure bleeder while activating DSC? When you activated DSC pump, did you have someone monitor the reservoir level? INPA screen happens so fast that you might not have a chance to get out of the car and top off the reservoir.

[KnighTT]

I did bleed everything first with a pressure bleeder.
I did keep the level of the res up while bleeding but one time it did go dry. I've bled 3 times since then to get any air out.
I did have the pressure bleeder on during the INPA bleed procedure, the one with the DSC pump, and this time around I'm going to keep the pressure bleeder off.

The code I am getting is air in the system and air in the Rear left. I've bled the rear left twice since getting that code and I immediately lose brake pressure as soon as I start up the car.

Pedal pressure seems to be fine until you start up the car. That's the part that seems off.

[Suvorovo]

"3 times" might not be enough to bleed the system. How many liters did you use? I would think 3Liters (6 500ml bottles) is plenty to bleed out the air in the system.

Also make sure your pressure bleeder doesn't fall below 10psi. Brake bleeder at 1Bar kept the reservoir full.

(I did a straight brake bleed on my e90. Took 2Liters. No INPA activation due to bugged xdrive DSC activation in INPA)

[edycol]

Pedal going to the floor tells me that you are loosing pressure somewhere. Bit of air in the system would create spongy brake feel but not pedal going all the way to the floor.
Did you replace lines?

[KnighTT]

That was what really started all of this mess. I pulled the calipers off to paint them and I replaced all of the brake lines with SS lines from ECS. New pads and rotors.

I may have found out the issue, maybe.

Every time I bleed the system the pressure seems to be great until I start the car. I start the car up and it basically goes to the floor like a baloon deflating and you have to pump it a few times to get pressure. It's not slow, it's a fast deflation of pressure. So it's not a slow leak. I originally thought the master cylinder may just be old.

I also hear kind of a air leaking through a bellow sound when the car is off when you pump the brakes after it has sat for a bit. I did a few bleeds today and the pedal is firmer than ever but I tried something out.

I took OFF the vacuum line to the brake booster. Boom, pedal doesn't go to the floor when the car is running. Obviously not a solution, but a sign. I don't think the brake booster is keeping vacuum.

So I put the line back on, while it was running, and the pedal just goes right to the floor. You have to pump it a few times to get it back to firm.

So, I go looking to see about the brake booster line and vacuum. There is a check valve right on the line as it goes into the brake booster. I wonder if that check valve is dead. There was even a TSB about it.

SI B34 06 07
Brakes November 2007
Technical Service

https://www.ecstuning.com/b-genuine-...e/34337577336/

This is the part from ECS.

I actually have another e92 sitting in the garage and I'm going to yank off that line and check valve, swap it over, and see if that resolves the issue. Praying....as if that is the issue it's just a ~$30 part.

[KnighTT]

I replaced the rubber gromet and the brake vacuum line with the check valve. This didn't help.

I got under the dash and saw this. I'm starting to think I need a new brake booster?

[KnighTT]

I went ahead and ordered a new ATE brake booster from FCP. ~$198

All the videos I saw seem to point this being a diaphragm failure. There is a hissing or air leaking sound when you press the pedal. When the engine is turned on the brake pedal will go all the way to the floor with little effort. You wait a few seconds and it will do the same thing again. I think this is a bad diaphragm or the internal valved system. There is fluid around bellow and push rod where the booster attaches to the brake pedal. A video says this is due to oil getting into the diaphragm assembly and it breaks down the rubber.

The real CON here being to get the brake booster out I'll have to drain the brake fluid, remove the lines to the DSC, remove the master cylinder, and then pull out the booster. Then.....refill and bleed the brake system repeatedly until it is back to 100%. Again.

[KnighTT]

I also said screw it and ordered a new master cylinder. Both ATE. Just in case. If I'm ripping it out, mine as well replace both and there is a much lower chance of not fixing this issue.

[KnighTT]

A new brake booster and a new master cylinder didn't fix the issue. I bled the brakes a few times then ran though the ISTA automated brake bleeding and I still have the exact same issue.

I'm at a loss now. I have reached the end of trying to DIY this.

[Suvorovo]

Originally Posted by KnighTT

I replaced the rubber gromet and the brake vacuum line with the check valve. This didn't help.

I got under the dash and saw this. I'm starting to think I need a new brake booster?

When you replaced the grommet on the brake booster and vacuum lines, did you have to disconnect the DSC pump? Is it enough to just unscrew it and push slightly to the side?

I need to do my vacuum lines soon, kinda sad looking.