Brakes pedal not firm after M50 swap

[g22]

I've got an e30 325i with an M50tu swap. I'm running a remote reservoir on an e32 / e34M5 master and booster with E30 M3 brakes all the way around.

After working on the swap for the last 6 weeks I've finally completed the motor and suspension / brake swap. I've bleed the brakes 3 times now with little to no air coming out the last time but I've still got a soft pedal.

I see no leaks. I've also took out the vacuum line from the booster, plugged it to see if the car stopped with no boost and the pedal was hard. I beleive that means the the master is working.

What should I check next? I've got o'fest in two weeks so I've got to get the brakes working well.

Not having confidence in the brakes makes you very very slow around road A!

[Massive Lee]

More bubbles are still trapped.

[g22]

Lee, I had a feeling you would respond. What would give you the impression more bubbles are trapped? Also, how the heck to I get them out if the last time I bled them there was no air?

Also, on another note I bought those 15 inch TRmotorsport wheels in E30M3 format so I'll check if the brakes clear and let you know...

[e30s52]

Did you bench bleed the MC?

[g22]

Okay, I've swapped an engine but I've never bench bled a MC. Can you educate me on this?

[e30s52]

remove from break booster, then you add the adapter to where the lines would go, after that you take rubber lines and rout them through the adapter back into the top of the resivoir, press in on the rear of the MC.

If you search on google or on here I am sure there is a step by step way. I hope that helps.

[g22]

I see what you wrote but its not clicking. I'll search.

Although, do you think that after bleeding the "traditional" way won't clear the air?

[Massive Lee]

It takes a small bubble to make the whole system spongy. I have learned that the best way to bleed a system, especially after installing a master cylinder, is to use a pressure bleeder. Basically you need to buy a quart of cheap fluid and have a friend help you. While the pressure bleeder gently pushes the brake fluid at 10psi, someone presses the brakes on and off, while the caliper's bleeder screw is open. Press the brake pedal to the bottom, release, press again. Do it slowly. Repeat 10 to 20 times. That shall bleed the MC properly. You can reuse the cheap (but clean) fluid until the pedal is rock hard. When you have a clean system, then bleed again with higher quality fluid.

[g22]

I'm using a Motive pressure bleeder. With the swap it will take me a while to pull the master to bench bleed it. I'm going to try the pressure bleeder and have someone tap the brakes while I bleed at the caliper. Thanks guys.

[MR 325]

I would bench bleed the master and then bleed the master again once installed in the car.

After that, bleed at the calipers as usual.

[g22]

I've searched google and here and must be stupid becuase i still don't get how i'm going to do this. I don't have any extra fittings, what else can I use?

http://www.r3vlimited.com/board/showthread.php?t=105435&highlight=bench+bleed

[MR 325]

Auto parts stores will sell a bleeding kit.

[g22]

I'll head to autozone today. thanks again.

[g22]

I think this issue is related to my abs not working issue. After continuing to bleed the pedal is firmer but the abs is not working...

http://www.r3vlimited.com/board/showthread.php?p=1679345#post1679345

[bostonbmw]

I don't see how your ABS not working would give you a soft pedal.If your ABS is not working and you have a soft pedal I think those are 2 separate issues unless your leaking fluid from the ABS(unlikely). Did you properly Bench Bleed your master cycl like MR_325 said?