Hi All,

Car is a 17 countryman S all4 6mt (if that matters)

Reverting my car to stock, so I removed my JCW brake calipers and rotors and replaced them with the OE units.
Not my first brake rodeo.

Once the OE hardware was in place, i opened the brake reservoir and topped it up with fluid.
Attached my Motive Power Bleeder to the master cylinder and pumped to 15psi.
I use the "dry" method with my motive (i.e. the motive tank stays empty - just used to pressurize the lines)
I am very good about checking the master cylinder reservoir, so 99% confident it never ran dry
front passenger caliper is spitting serious air bubbles out (sounds like someone trying to suck the last bit of milkshake out of a cup, rather than the usual tiny bubbles you look for when bleeding)
front driver caliper is fine, bleeds normally
I thought I got most of the bubbles out, took it for a drive. Brakes were okay, but kinda spongy.
Thought I'd attempt one more bleed before taking it to the local lube shop for a proper power brake flush
Same procedure as above, still a LOT of air coming out of that front passenger caliper.
Then went to leave the garage and almost 90% loss of brake function (car is now undriveable)
Tried swapping JCW caliper back to front passenger location to see if maybe the caliper seal was bad...no luck...still have same symptoms.

System holds pressure at 15psi (per reading on motive power bleeder)
No apparent leaks
Car ran and drove fine yesterday, so clearly something that I induced today through my caliper swap and/or bleed procedure
brake pedal goes almost immediately to the floor with engine running

What am I missing??

I suppose it could be a bad rubber brakeline at the front passenger corner, or could be seals flipped in master cylinder? I'm at a loss as to where all the air is coming from...

Thank you!!!

 

What did you do to keep the fluid from being lost and draining master cylinder while calipers were changed out?

 

Found a busted o-ring between the back of the master cylinder and the front of the brake booster - part number 34336799317

The vacuum system should be isolated from the fluid itself though, so I'm not sure how an air-leak on the power brake booster would result in air in the brake lines themselves.

Doesn't look like that part is stocked, so this may take a while...ugh!

 

I pinched off the rubber lines with vice grips for about 30-60 seconds while I hot-swapped the calipers (one at a time). no measurable amount of fluid was lost.

I guess it's possible I compromised the rubber brake line when I did that, but not sure how that much air could be getting IN through a hole I made, but yet no brake fluid coming out?

 

No just asked to confirm no air went into the ABS system, but you did what most of us do!!

 

I don't think this is uncommon, actually. And I'm not 100% convinced it's the broken seal you found. The same things happen on my 2021 GP3. Passenger front spits out what basically looks like froth. No amount of bleeding with get my brakes back to working correctly until I take it to a dealership and have them flush it. Annoying as ****, tbh. However, the last time I was there (last week), I asked what I was doing wrong where I couldn't just bleed the brakes myself. They said, and I almost quote: "you have to used a pressurized bleeding method and keep the pressure around 10psi. It's the only way to do it.".

Now, I'm not a mechanic, I don't play one on TV and I didn't stay at any Holiday Inn Expresses recently, so I won't say if this is entirely accurate or not. But, I will use this method to bleed them the next time I attempt it..probably in a few weeks.

I'm very curious if the broken seal you found actually fixes it, though.

 

FWIW I have successfully used a pressurized bleeder for my 2016 F54 and F57 with no issue.
I got this one from Amazon. YSTOOL Manual Brake Clutch Fluid Bleeder Kit Oil Change Bleeding Tool Set with 3L Hand Pressure Pump Refill Tank 1L Extractor Bottle Master Cylinder Adapter Caps Compatible with Ford Chevy VW Audi

 

I mean, I get there's an ABS unit involved, and cars are more complex than ever...but I don't understand how they can turn a 10 min job into a 1 week job (nobody has parts nearby) by way of how the brake system is designed.
Kicking myself for even attempting it at this point..ugh.

I did use a pressurized tool/system, but I was putting pressurized AIR in the top and not pressurized brake fluid...maybe that's the difference. I always thought those systems (when used per the instructions) seemed like a huge waste of brake fluid (and a pain to clean out the thing after every use), but honestly, the pain of NOT doing that now appears to be greater. lesson learned I suppose.

Ocramida, that's more or less what I used. Appreciate the tip! Sounds like I have the right tool, just need the right user :-)

I had a full set of parts (o ring, bleeder valves, rubber brake lines, caliper repair kit, master cylinder reservoir seals) ordered from Seattle Mini last weekend, but some of the parts were on backorder, so they hadn't even started pulling the parts from the PDC's yet...didn't feel like waiting 4 weeks with this thing in the middle of my garage waiting for a part to show, so I cancelled the order (they were super nice about it, btw, and not at all their fault).
Think I will track down the o-ring on it's own and at least re-assemble the car (engine bay plastics all removed AGAIN to access master cylinder). Worst case I will have it towed to the dealer or the local indy and let them futz with it.

My daily (F25 X3) decided to dump all the coolant out last time I drove it, so that's waiting in the wings for the next job here. Aaah the life of German car ownership out of warranty :-D

 

Update: put in the new brake booster seal, topped up the reservoir then tightened up the brake lines to the booster.

Filled my motive power bleeder with 1.5L of brake fluid (way overboard, I know...just didn't feel like taking another pass at this.

Bought a PAIR of the power bleeder bottles that you hook to the wheels (this made the work go a lot faster as I could have one bottle on each side of the car.

Cracked the bleeder valves and bled as normal, going back to the motive power bleeder and pumping it back up to 10psi every so often.

Went around the car like 4-6 times bleeding each corner...kept expecting a big bunch of bubbles...never happened. little champagne bubbles like it's supposed to be. it's almost like the "frothing" event I experienced before never even happened!

Put the wheels back on and went for a drive, brakes feel pretty darn good. I'm sure a dealer with ISTA could tighten them up a bit, but since I've been driving with the JCW calipers/pads/disks more or less since I bought the car, it could be that this is just how the stock brakes feel. practiced a couple panic stops from 40mph or so, car hauled in pretty well.

so, conclusion here for all those that find this thread later:

In order to properly bleed a 3rd Gen Mini (F5X, F60), use a power bleeder to push fluid (not air) through at 10 PSI, and you should be good! :-)

 

Something about that name keeps me from getting interested!!

 

Can you store brake fluid in the Motive bottle? Or have you returned the unused into the cans.

 

I had my previous Mini mechanic over to my place a couple weeks ago to green some knowledge from him (actually, traded some SS brake lines for the info). He was the one who worked on my 2019 JCW with the big brakes and my GP3. He said he always had issues bleeding my brakes in their shop (Mini dealership) until he got a specific tool:

https://shop.snapon.com/product/Vacu...Bottle/BB5002A

Once he got that, no more bleeding issues. So now I have one. And I bled my brakes over the weekend after my track day. Worked a treat . Granted, it still the older-school 2 person brake job, but, my brakes are stiffer than they've been in a while and working great! Buttonwillow here I come!

 

I had problems last summer when I changed by brakes. 2 types of vacuum pumps didn't work. I was going to try a pressure bleeder but I read about just cracking open a valve and letting it bleed for a good while. Worked like a charm.

 

Thanks for the info. I am thinking about attempting this. Just wondering if you bled the clutch slave as well, and if so where that is located and how difficult it was. I know it shares the brake fluid.

 

Save the $70, and hand your neighbor a beer while he keeps your M/C topped off as you're bleeding!!