Brake issues with swap, e36 m3 calipers, e30 m3, and new 25mm master

[HinzM3]

Hey guys the car has e30 m3 rear calipers, e36 m3 front and I rebuilt all 4 calipers. I installed the e30 abs sensor in the e36 spindle up front and of course the e30 ones fit in the rear. Also upgraded the master from Bimmerworld with the 25mm. Issue i'm having is the pedal just sinks to the floor and the brakes just don't work. If I pump them eventually around the 2nd or 3rd time I get some brakes. I've bleed the system the manual way and pressure bleeding about 6-7 times. No air comes out of the system. Having a hard time finding the cause.

Bad master? I was a dumbass and chucked my old one on a cleaning spree so I can't just throw that back in. I also tried with no vac to the booster and its the same situation just with no assist, pedal still just sinks. Does the abs need to be cycled? I tried to drive it around and engage abs but my front left locks up...

[HinzM3]

I checked for leaks, have all new SS lines as well. When I replaced the master the bentley doesn't say anyting about bench bleeding it, do you have to do that on an e30? I know on my old fj40 I had to bench bleed the master when I replaced it.

[2002maniac]

yes, MC's should always be bench bled. If you hadnt mentioned that I would have said bad MC.

A little air in the lines or ABS unit wouldnt cause the pedal to sink like that, it would just be squishy at worst.

[HinzM3]

so take it off and bench bleed? I thought that was weird when the bentley didn't say it. The master also didn't come with the little plugs/lines to bench bleed either. Will give that a shot today

[Rocla]

Front calipers swapped from right to left?

Bleeding niplles should point upwards, if they point downwards air will not exit from system.

[rede30]

Front calipers swapped from right to left?

Bleeding niplles should point upwards, if they point downwards air will not exit from system.

if you dont bench bleed the system and you have bleed everything a few times you should have decent pressure. A long while back i didnt bench bleed and i just bleed the system three times and everything felt almost normal. Not perfect so you shouldnt do this but it seems like your brakes should be better than what you discribed. Try what Rocla said that makes the most sence.

[HinzM3]

Front calipers swapped from right to left?

Bleeding niplles should point upwards, if they point downwards air will not exit from system.

They are on the correct way and both point upwards. Just double checked them. The rears are on correct as well. I think the calipers actually said L and R if I recall correctly.

if you dont bench bleed the system and you have bleed everything a few times you should have decent pressure. A long while back i didnt bench bleed and i just bleed the system three times and everything felt almost normal. Not perfect so you shouldnt do this but it seems like your brakes should be better than what you discribed. Try what Rocla said that makes the most sence.

Yeah its definitely not driveable unless its just around the neighborhood.

[Massive Lee]

You have a lot of air in your lines. You will need two quarts of regular/cheap fluid. Use a pressure bleeder and squeeze the brake pedal all at the same time (this will be as efficient as bench bleeding the MC). This method will also get rid of the bubbles in the ABS pump. Waste as much fluid as you can get (which is why I advised cheap fluid). After you have done all 4 corners, you should be good. Then you can start using higher quality fluid.

[browntown]

I bleed the clutch slave too, I generally do it between the rear and front tires. Furthest to nearest. Don't know if it's neccessary but I figure it's all the same system, might as well.

Pressure bleeder for the win, got mine from pelican for 35 bucks or so, great investment.

[matt]

I bleed the clutch slave too, I generally do it between the rear and front tires. Furthest to nearest. Don't know if it's neccessary but I figure it's all the same system, might as well.

Pressure bleeder for the win, got mine from pelican for 35 bucks or so, great investment.

It's actually not the same system... it just uses the same reservior.

I agree, you need to bleed the brakes much more thoroughly. I didn't bench bleed my new MC and it bled fine. My brakes are stiff as all hell with stock calipers and an M5 master.