Hello, everyone. Long-time lurker, first-time poster. Sorry my first post is under such circumstances, but such is life I suppose. Sometimes you just need a leg up.

I've got a 2003 Mini R53 (build date 01/03). Here's an older pic; it's on a set of Clubman spoolers now:



Early this year I went out to my Mini one day to go to work, fired her up, dropped the handbrake, and...the brake light stayed on. Having recently done the brakes all 'round I was confused, but took a quick look around to be safe. I didn't see anything out of the ordinary (brakes looked fine, no visible leaks) except that the brake fluid was low. I topped it off, the light went away, and I chalked it up to just being one of those weird random things.

Another couple of months later the same thing happened. Again I took a look around and didn't see anything odd. I did a few Google searches and checked some of the other potential trouble spots I hadn't thought of (most notably the clutch slave and clutch master) and still didn't notice any leakage. I topped the brake fluid off once more and continued on my way, but this time with a noticeable difference - my brakes weren't as firm as before.

Fast forward another couple of weeks and my brake light came on once more, again with low brake fluid. By this point I started having a noticeable issue with my brakes. Under firm pedal pressure the pedal would feel like it was very slowly "bleeding down" towards the floor (though never actually bottoming out). The transmission was also having some issues shifting into first gear - it would always go in, but it didn't feel particularly happy about it (noticeable increase in required effort). Ok, three times is a pattern and now I have noticeable symptoms; it's time to do something about it.

I ordered a brake master cylinder and a clutch slave cylinder and set up a weekend to pop 'em in with a buddy of mine who's a mechanic at a Volvo main dealer (his tool set and experience being much more comprehensive than mine). We got the items swapped out in less than an hour, bled everything with a vacuum bleeder (including running through the ABS bleed procedure using a scan tool), and thought we'd have the job done before lunch.

Nope. Everything went straight to the floor.

Around this time I noticed some brake fluid leaking near the rear of the car. On further inspection the left rear hard line was leaking due to corrosion. We patched in a new section of bend-your-own line (all correctly flared; no kinks) to bypass the corroded section and bled everything again, checking every square millimeter of line in the car for further leaks. Didn't see any leaks and the pedal seemed rock-hard with the car off, so I fired it up.

Still no visible leaks anywhere, but the initial brake pedal issue returned - mushy feel and slowly bleeding down to the floor.

Meanwhile I had been reading up on the clutch slave cylinder bleeding procedure and determined our method of piston compression wasn't cutting it. I went out to a Home Depot and got some plumber's tape to exactly replicate the "Mod Mini method" of clutch slave bleeding. This time around we seemed to be getting plenty of air out of the clutch slave. We bled and tapped and wiggled and bled some more until we were confident there was no more air left to come out. Got in the car, fired it up, and...well, it would go into the gears with noticeable effort but definitely wasn't right. About 2" of travel at the top of the pedal before encountering any resistance at all, then a somewhat-firm-but-still-kinda-mushy feel to the floor. Clearly the clutch wasn't disengaging fully. At this point my thought was that some air had gotten trapped in the clutch master cylinder. I did some more lurking and came across the "prop the clutch to the floor overnight" method. Since my buddy and I were exhausted at this point (almost 10 hours of bleeding will do that to you!) we wedged some socket extensions in between the pedal and the driver's seat to keep it pressed to the floor and called it a night.

The next day (after sitting about 12 hours or so with the clutch pedal pressed in), I went back to his house and got in the car. The clutch felt great and the transmission would shift into all the gears. Took it on a quick test drive and the clutch issues seemed to be gone, but the brakes were still slowly bleeding down - this time to the floor on occasion. Got it back on the lift, went through the bleeding procedure another 3-4 times, and still didn't have any luck. My mechanic friend suggested it was because he didn't have a pressure bleeder, so I limped the car home and made an appointment at a "Mini specialist" shop to bleed the brakes (I have no Mini dealer in my area). By the time I got home the clutch was not quite right again (tough to get into gears). Left the car sitting overnight, got up in the morning to drive it to the shop, and the clutch was gone - wouldn't go into ANY gear. Out comes the rollback:



The "Mini specialist" shop was...well, let's just say it was an adventure. For brevity's sake (since this is already becoming a wall of text) I'll give the TL;DR version - they said my brake fluid reservoir was cracked so they couldn't pressure bleed the system (though I'd never noticed any leaking from there), so I ordered a replacement myself, dropped it off, and had them install it. They then said they were able to bleed the clutch, the brakes were still slowly bleeding down, however the car was "driveable," and my bill was $400. They recommended I get a new ABS module and quoted me $130 for a used module and another $700 for labor. At this point I told them to go pound sand and went to pick up my car. Brakes go straight to the floor and the clutch is back to the "two inches of free travel, then mushy firmness" status (but it *does* go into gear, albeit unhappily); not the "driveable" status they told me it was. Had it towed again, and that's where we stand now.

So, after $500 and three weeks' time I've gone from "driveable but getting sketchy" to "completely undriveable." Kinda moving in the opposite direction than intended.

I need some help/advice. I'm not sure what I'm doing wrong or how to proceed. In an attempt to preempt some questions, here's a few things I DO know for sure:

1. The actual clutch (in terms of the friction disc and pressure plate) is fine. It was replaced about 25,000 miles ago, hasn't been driven hard, and has never slipped or otherwise given any indication that the clutch itself is bad. Clutch was 100% driveable prior to this job, and has always been firm (almost to the point of being excessive; I bet my left leg is stronger than my right).
2. No codes of any sort have been tripped in the making of this mechanical mess.
3. All four calipers have been off the car within the last 6 months for pad/rotor/hub replacements; no noticeable issues with any of them at the time.
4. Since that section of brake hard line was replaced, there have been zero noticeable hydraulic leaks anywhere.
5. At no point during the various bleed operations did the reservoir fluid level drop to the point where air could be introduced in the system.
6. One thing I should mention is that there has always been a slight but noticeable hissing sound from the brake pedal area inside the car (similar to a vacuum leak), but ONLY when the pedal was at the top of its travel (i.e., not being pressed at all).

And here's a few direct questions:

1. Was the shop's suggestion that I need a new ABS module valid? If so, how does one go about replacing it with a used unit? I've got a friend who has various BMW computer reading/writing things (he's got a couple of more modern BMWs) so re-coding is doable, as is the "ABS bleed procedure."
2. Is my intuition that there's air in the clutch master cylinder valid? I'm basing it off that whole "first couple of inches have zero pressure" thing. If so, how do you get it out of there?
3. Do I need a pressure bleeder to do this? Is that really a vital component to the process?
4. Is there some vitally important thing I'm missing/forgetting?
5. Am I completely screwed?

I would be eternally grateful for any help you can offer. I know my car's 16 years old now and many people would say "just give up on it and get a new one," but...I don't wanna. I like this one. I want to save it.

Thank you.

-Pet

(PS: This may end up being a double-post; the first time I attempted it it said to await approval but it's been over 24 hours and my User CP says I have zero posts, so trying it again. Sorry, mods.)

 

Hmm; my thread was finally approved. I'd kinda given up on it, but now that it's here I'll give an update.

Figuring we'd start with the brakes, I got the car up into a friend's garage and let him do some troubleshooting with a pressure bleeder:



The first test was to place the pressure bleeder on the fluid reservoir, crank it up to 20 PSI, and leave it set overnight. The hope here was to either see a reduction in bleeder pressure or see fluid leaking from somewhere. The results were...well, not what I'd anticipated:



Very slight reduction in pressure, and no visible leaks anywhere at all. Grabbing a front rotor and attempting to give it a turn showed the braking system to be under sufficient pressure as well, not just the fluid reservoir. Very odd.

So, my buddy busted out his laptop and USB -> OBD cable, fired up all his BMW software whatevers (he's got a 3-series and is into all that electronic stuff that I'm totally clueless about), and pulled up the official BMW DSC brake bleeding procedure. This involved cracking the bleeder at the caliper (starting at the right rear), running some program on the laptop that causes the ABS/DSC to engage for a few seconds, then pumping the brake pedal 5 times and closing the bleeder. On the first go-round we saw tons of air from the right rear bleeder, but none from any of the others - just solid, clear fluid. Some pedal feel came back after this, but upon starting the car and giving the brake pedal a push all the pressure disappeared again.

We decided to give the procedure another go-round, again starting with the right rear. Again a ton of air came through the bleeder. At this point we decided to just cycle the ABS/DSC module repeatedly with the bleeder open until no air came out. Unfortunately, this never happened - every time we'd engage the module, more air would come out. Another close examination of every square millimeter of the braking system showed no fluid leaks anywhere, aside from maybe some slight "moistness" on the threads of some of the line fittings at the ABS/DSC distribution block. Going around all four rotors and giving them a turn showed that while the braking system was under pressure from the bleeder, all of the rotors were immovable except for the right rear.

So, we took a break and had a think:

• Still no fluid leaks, which is bizarre given the braking issues.
• Air is obviously being introduced in the system somewhere despite the lack of leaks.
• We think the master cylinder is ruled out - it's brand new, and if air was getting into the system from the master cylinder it would be showing air at more than one caliper.
• We think the right rear caliper is ruled out - it's been off the car recently and was seen to be in good working order, and another visual inspection shows no issues.
• We think the lines (both hard and soft) from the ABS/DSC distribution block are ruled out due to the lack of visible leaks or noticeable damage.

This, in our minds, leaves the ABS/DSC module as the only plausible explanation. There's no other way we can think of that air would be being introduced to only the right rear line.

Unfortunately this leaves the prospect of either getting a new module from BMW (they quoted me $2,800!) or a salvage yard. There's one near my house that has one for $40, so for that price I think it's worth taking a punt on a secondhand one. However, I also understand that these have to be coded to the car as well. That's something I know less than nothing about - however after a quick Google search finding a post saying something about "NCS," my buddy said he thinks it's not that big of a deal to do.

So, that's where we are now. If anyone thinks our reasoning is faulty, or has any other ideas, I'd love to hear them. Also, any help in regards to the process of recoding an ABS/DSC module to my car would be appreciated as well.

 

I don't see how you can get air in a closed system without losing brake fluid.
It may be a bad ABS unit. Still fluid has to be going somewhere...
After you bleed again put some clean paper under the whole car.

 

Thinking about your bleed-down test. It's not very sensitive.

Assuming that tank holds 2 liters of air (guessing here) and the temperature was initially at equilibrium, pressure went from 20 PSIG to 18 PSIG. That's about 35 PSIA to 33 PSIA. To do that, the air expanded into a volume 35/33 as large, or 6% larger. If this happened by incompressible brake fluid leaving the system, that's a loss of (2 L)(6%) = 0.12 L = 120 cc. That's a significant loss.

Did the level in the reservoir drop?

 

It didn't make sense to me or my buddy either. Then again, few of the issues I've had with this car have made much sense, lol.

It's a clean garage floor and I was beyond meticulous in my searching for leaks. Didn't see a drop anywhere.

The level stayed constant (I made sure the tank on the bleeder was marked prior to the test).

In the interest of keeping this thread going, I'll give a bit of an update. I picked up a used ABS/DSC module from a local salvage yard for $40; it came out of an '05 MCS with 90k miles on the clock. My buddy recoded the replacement unit with...uhh...whatever that BMW software thing is he has. We swapped out the modules (ended up being an easier job than I thought it was going to be) and cracked open the old one just out of curiosity. One of the seals looked a bit gnarly, so that gives me hope that we're going in the right direction.

Unfortunately we didn't have time to bleed the system yet, but should be starting on it tomorrow. Here's hoping.

 

Another update:

Started the entire bleeding process over from scratch. Manually bled all four lines, then did the BMW ABS/DSC bleeding procedure twice at each wheel. Pedal feel was slightly better than it had been but still far from right (was nearly going to the floor, but had more resistance than before). However, this time we weren't noticing any air from any of the lines while activating the ABS/DSC, which tells me that the old ABS module was indeed faulty.

During one of our brake pedal checks we noticed that depressing the brake pedal was pushing fluid from the reservoir back into the pressure bleeder. This made no sense to us - why would the master cylinder be pressurizing the brake fluid reservoir? We removed the bleeder and visually monitored the brake fluid level while pressing the pedal. Sure enough, the fluid level would rise when we pressed the pedal, and go back down when we released it. The only thing we could determine from this was that my "new" master cylinder (actually a remanufactured one) was itself faulty. I still had the original master cylinder, so we swapped that in and rebled the system once more. Immediately the pedal feel improved dramatically - but it's still bleeding down slowly under constant pressure.

In short, I think I ended up replacing a bad master cylinder with an even worse one. Best guess I have is that some sort of internal check valve in the remanufactured master cylinder was installed backwards, causing it to pump fluid into the reservoir instead of through the brake lines. Good job, Cardone. So, I guess I have to navigate Rockauto's return policy now. In the meantime I'm going to order a third master cylinder (a legit ATE one this time) from FCP Euro and hope that finally solves the brake issue.

Haven't gotten around to fully rebleeding the clutch yet. Rigged up my piston compression tool and gave it a couple tries under pressure from the bleeder, but it's tough to see if any air is coming out - the fluid just sprays out at great velocity and in great quantity. I think next time I give it a go I'll put my bleeding tube/bag on the thing so I can see if any air is escaping.

 

Interesting thread. Curious to see how the saga ends.

 

Well, the brakes are fixed now. Threw the new master cylinder in, re-bled the system for the thousandth time, and the pedal came back. Despite bleeding the living crap out of the system and not seeing any more air coming from the lines the pedal is still a bit spongy, but it's no longer bleeding down and the car stops fine.

However, there's still some kind of issue with the clutch. I'd compressed the clutch slave piston with the "MOD Mini" method and once again bled the system, this time with the speed-bleeding tube/bag on the bleeder to be able to see any air escaping. Got nothing but clear fluid, so I removed my "compression tool" and reinstalled the clutch slave. There was still 1-2" of blank pedal travel at the top of the range that I don't remember being there before, but the clutch seemed to be disengaging fine and the car would go into all of the gears. Put the car back together and took it on a test run and the car drove fine, but the clutch still didn't seem "right". Very spongy pedal feel.

I left the car sitting for a couple days while I went out of town. Coming back to it, the clutch has somehow worked itself to a non-functioning state - lots of loose pedal travel at the top and the clutch is not disengaging again. Putting the bleeder back on the clutch slave and re-bleeding brings only clear fluid and a minimal change in pedal feel. Once again, there's no discernable leaking in the system anywhere. Considering the entire clutch hydraulic system only has two parts and one of them (the slave) is brand new, the only thing left to be faulty should be the clutch master cylinder - but that looks fine too:



I don't see how the clutch system can be introducing air by just sitting statically without leaking somewhere. Ugh...this damn car...

Again considering there's only two parts to the system, I'm left with two options that both seem pretty unlikely:

1. The clutch slave cylinder (despite being new) is also faulty just like the brake master was, meaning 100% of the parts I'd initially ordered were somehow bad from the factory.
2. The clutch master cylinder is also faulty, meaning the ABS/DSC module, brake master cylinder, clutch master cylinder, and clutch slave cylinder all failed almost simultaneously.

I suppose there is a third option - that I somehow damaged the clutch slave during the repeated reinstallations while trying to fix the car. I didn't exactly beat on the thing, but I wasn't perfectly gentle either. I'm not sure how fragile they are. At this point I'm tempted to just buy both a new clutch master and another clutch slave and replace everything again - a pricey prospect but I don't know what else to do.

Is there something I'm missing/doing wrong here? Any ideas?

 

I had a couple issues with bleeding my brake system after the rear brake lines failed from rust. I ended up doing the ABS bleed function on my code reader, using the pressure bleeder on the master cylinder, and then compressing the brake and clutch pedal with a long stick (locking it into place by moving the seat far forward) and leaving it overnight. I then drove the car for a couple days, and then opened up the bleeder screws on the calipers and that finally got the last bit of air out of the system. It takes considerably longer than you think itll take, but i've finally gotten the pedal feel back to 100%.

 

Sounds like you did actually have a bad master cylinder and a bad ABS, and might have a bad clutch master. Did a previous owner decide that DoT 5 must be better than DoT 4 and wipe out the whole system? Could be.