Suspension Brakes 1st Gen JCW 56 Brembos on my R53 fell like Mush

Sounds like there is still air trapped inside somewhere. Let it sit overnight and try bleeding it again. Also how are you bleeding them?

 

MINI brake lines can be hell on getting all of the air out. I also think there's a bubble or 3 in there somewhere.

 

Keep bleeding. Try tapping on the caliper with a rubber mallet as you bleed.

 

Is the caliper moving smoothly on the pins? If it's flexing it can give a mushy pedal, but I think you still have air in there somewhere.

Are you using 2 people to bleed or just opening the lines till you get clear fluid?

What bleed method are you using?

 

The R56 JCW Brembos are 4-piston fixed calipers.

This is my favorite how-to on bleeding brakes: How to Bleed Brakes

 

By the description it sounds like air still in the system.

The article posted about bleeding is pretty good but, one thing overlooked in bleeding is that the threads on the bleeders can pull air back into the lines or caliper.
Remove the caliper bleeder nipple, clean its threads, and then wrap a short length of Teflon tape around the threads to help seal it from air entry or fluid leakage during the process, then reinstall the nipple to the caliper.
or:

Speed Bleeder are a one-person brake bleeder screw that bleeds fluid and air from your brake caliper. They have a check ball which allows fluid and air to be pushed out and than closes between pumps, preventing fluid and air from re-entering the caliper.

 

I wonder if he's describing the problem accurately, since he seems to think the size of the caliper is causing the problem....

So, to me a mushy pedal is one that doesn't really get a lot better if you pump it, where a low pedal does get better if you pump it.

The first would inidcate air in the lines, the second would indicate not enough movement for one stroke of the master cyl, as when the pads get bumped back by warped discs and it takes two strokes to move them back out, or if the master cylinder is sized wrong and won't fill the cups with one stroke.

So which condition do you have?

 

Too bad more vendors don't like to post in these kind of threads? More shops giving information based on there experience is always welcome?
There are many Big Brake Kits on the market for the MINIs today then ever before. None that I know of come with a replacement master cylinder? I do not know of any of these BBKs having issues with the oem master cylinder? The R56 caliper by volume is smaller than some of those BBK available?
Contrary to many who have flushed and or bleed MINIs it is not always as easy to accomplish even with a scan tool and pressure bleeder as one would think.
I had a reluctant 04 after a BBK install that I finally opened all the bleeders and let it gravity bleed overnight and than used the pressure bleeder the following day to finalize the job.
And others that I had to do several times to get both no air and a hard peddle.



The advise I see is if you have good brakes but spongy peddle than carefully drive to a shop and let them finish the bleeding procedure and don't take a chance on a questionable finish with regards to your brakes!

 

Well if I were you I would get rid of that ATE blue fluid. I see spongy pedals all the time with it, no matter if it is new or old that stuff does something to the seals and it's not good. I would recommend Motul.

As for bleeding, the old fashion way works best, no need to run the ABS, the valves when the car sit in a neutral place so you can bleed it without the pump running. Running the ABS and bleeding is just asking for air bubbles. Start at the furthest away from the master cylinder and work your way to it.

RR
LR
RF
LF

 

I bleed my brakes on my mountain bikes and I hate it. Now I know why I don't bother with the car brakes

 

Best thing I ever bought for doing the brakes is a Motive brake bleeder.... After that you most likely do have air trap in the system, my guess would be in one of the calipers. Make sure all lines are tight and know its a pain but you might try recompressing the caliper pistons and start over with a good bleed starting as said earlier RR,LR,RF finishing at the shortest line the left front. Make sure all bubbles are gone from each caliper before moving on, then check the peddle. It should be firm. Then start the car and see how they feel, drive it a bit and then do another short rebleed in sequence....2 cents

 

I'm just going to throw something out here.....

Been reading about the ABS pump valves needing to be opened via the OBDII port to vacate any air out of the pump body. Good possibility even after you get the air out of the lines, the first time the ABS kicks in, you may feel your brakes go soft again. Air bubbles being pushed out of the ABS pump. This may require another bleeding.

I don't know if the Motive pressure bleeder would get around this issue? Others on the forum might know this?

 

It's somewhat of an internet myth. Unless the ABS is working, the valves are closed. It's very hard to get air in the ABS system unless you're replacing an ABS module. Even if you disconnected the hoses, the ABS valves would still be closed, and the fluid would not escape (unless you let the car sit for a long time). If you think about it, the ABS's action is to relieve pressure, just a little bit at a time and very quickly. If you push on the pedal and lock the brakes up, the ABS relieves pressure and allows the wheel to rotate again, and then it closes the valves. You have to keep pushing on the pedal to supply pressure, and the ABS relieves a little pressure over and over again and causes the brakes to pulse. So the default setting would be closed.

It's very hard to get air in the ABS module unless there are severe extenuating circumstances, and a machine bleed won't help 99.99% of the time. I've heard this confirmed by a couple different trusted mechanics, too.

 

That's good to know....

This was one of the posts I came across....

Ryephile
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Clutch and brakes share the reservoir, but NEVER BLEED THE CLUTCH unless you replaced the slave cylinder.

Start with the longest line run from the reservoir to the calipers [left rear, then right rear, then left front, then right front]. Power or pressure bleeders sometimes work but 2 person pedal-pumping works best with the MINI because it's a weird car. If you have an OBDII scan tool that opens the ABS valves then you're super golden, otherwise don't be mad when you have to re-bleed the system two days later after you've actuated the ABS and found a boatload of air or old fluid in the system still.

My best advice is to NEVER allow the reservoir to get near the minimum marking line. In my experience, the Min marking on the MINI is actually "You've already sucked in a Hindenburg sized gulp of air and you're screwed for days cuz that's how long it'll take to get the air back out of the lines and ABS module".

 

Ah, good point. I guess air in the ABS would be more likely to happen if you let the reservoir run dry.

 

Also, good advice on bleeding the clutch. Don't touch it unless it's broke. And have a good mechanic (like Dan at Grassroots) do the job unless you have one of the nice special BMW tools to bleed it. Just went through that myself.

 

Excellent to see you have a good hard pedal, a mushy brake pedal sucks and is not very confidence inspiring. Those Brembos are great looking behind the wheels.