C-R12's 2012 Alpine White 6/MT 128i Build Thread

[cerealwars]

Great thread dude! I loved reading this. Makes me nostalgic for when I was green. Your perseverance and passion really shows through. Excellent selection of mods by the way, you'll really hit the ground running.

I also admire your humility, increasingly rare to see (especially on the internet!).

I vote you do an HPDE or a track day. Once you get good enough to start smoking the brakes, then do the upgrade. Oh, don't forget to code out the nannies and watch your oil temps. I shut my session down when I hit 290*.

[C-R12]

Originally Posted by tracer bullet

Nice job, and thanks for the updates. Yeah it takes time to get comfortable working on things, knowing you have the ability and tools to *eventually* get through any project. And how hard to pull on plastic pieces, though I don't think anyone ever quite perfects that one.

I also have a hole in my garage wall from a jack handle. I had the front wheels on ramps and was lifting by the rear diff (this is my X3 actually). Instead of pulling the jack inwards when the back was going up, it instead pulled the car off the ramps. One of them anyhow, one tire on a ramp. I had so much adrenaline going and was so mad at myself it took an hour or more before I went back out to try again. I was coming at it at a slight angle and yeah the handle hit the wall.

Thank you! Yeah I think once I realized that I'm not a shop and won't be able to turn around every job in a day I started stressing less and began improving at working on the car. Glad you're ok with your jack handle incident too!

[C-R12]

Originally Posted by cerealwars

Great thread dude! I loved reading this. Makes me nostalgic for when I was green. Your perseverance and passion really shows through. Excellent selection of mods by the way, you'll really hit the ground running.

I also admire your humility, increasingly rare to see (especially on the internet!).

I vote you do an HPDE or a track day. Once you get good enough to start smoking the brakes, then do the upgrade. Oh, don't forget to code out the nannies and watch your oil temps. I shut my session down when I hit 290*.

Thank you! I'm happy that I've been able to start with mods pretty quickly after getting the car and yeah I don't mind being humble lol I'd rather get flamed for not knowing anything rather than get flamed for acting like I know more than I do, especially since I'm just starting out and so many more people have a lot more experience than I do.

The plan originally was to do a track day before the summer ended. I went to a BMW meet at a shop not too far from me and the owner had extra passes to take people to Atlanta Motorsports Park. He added me to the list, but I ended up being out of town for a wedding the weekend they had the track day. I do agree that I'm not at the point where I need to upgrade the brakes since I've only done street driving for the most part, but I'm actually currently upgrading the brakes anyway lol so I'll remember to code out the nannies this weekend

[C-R12]

I wanted to do better about posting about my car updates in real time, but I failed again. August marked my 1 year anniversary with my child, so I celebrated with a trip up to Helen to drive in the North GA mountains.







I've never driven in the mountains at all, but to do it for the first time in a sporty car that I also had put so much work into was amazing. There were a few times where I was driving outside of my abilities, but I still had so much fun, and I want to go back there for a drive soon. Unfortunately, on the way back down, my son came down with a case of the pre-cat-bank-2-o2-sensor-has-gone-bad-itis (2C3E & 2CA7) and it was back to the garage for a quick repair a few days later.

To recap my 1 year of ownership, I started with 130,598 miles and a car that looked like this:



And ended with 138,911 miles, exponentially more mechanical knowledge than I had before, and a car that now looks like this:



Definitely glad that I've been in a fortunate enough position to purchase this car and also have the opportunities to work on it and make it my own. I can't wait for everything I'll be able to do in year 2! (Hopefully that involves at least 1 trip to the track)

[C-R12]

Jumping to real time, my current project has been to perform the F30 Brembo front brake upgrade combined with the 42/20 rear calipers from a E90 328i. From my inspection report when I first bought the car, I knew that my rear brakes were low and I could tell that my brakes weren't the best after I had driven up in the mountains for a while, and since I've always tried to go for some sort of upgrade when I've needed to replace parts on the car, the upgraded brakes were next on the list.

I did a ton of research on the parts I would need to complete the upgrade, and I'll list those here:
- Blank Zimmerman F30 Front Rotor 340 x 30mm (x2) - 34116792223 - AutohausAZ
- Blank Zimmerman E82 Rear Rotor 300 x 20mm (x2) - 34216778051 - AutohausAZ
- Bowa Front Brake Pad Wear Sensor - 34356792559 - AutohausAZ
- Bowa Rear Brake Pad Wear Sensor - 34356792564 - AutohausAZ
- F30 Front EBC RedStuff Brake Pads - DP32130C - ECS
- E82 Rear EBC RedStuff Brake Pads - DP32069C - ECS
- 1 Liter Pentosin Super DOT4 Brake Fluid (x2) - BF1P4 - ECS
- F30 Caliper Dust Boot and Seal Kit (x2) - 34116850935 - BimmerWorld
- BMW Disc Brake Anti-Rattle Clip (x2) - 390577 - FCP
- BMW Caliper Pin Boot Kit (x2) - 34216869617 - FCP
- BMW Brake Caliper Repair Kit - 34116763995 - FCP
- BMW Brake Disc Set Screw (x4) - 34211161806 - FCP
- BMW Brake Master Cylinder O-Ring - 34311160617 - FCP
- BMW Porsche Brake Master Cylinder Grommet (x2) - 390090 - FCP
- E90 328i Brake Master Cylinder - 34336785664 - eBay
- E90 328i Rear Brake Caliper Pair - 34216768697/34216768698 - eBay
- F30 Front Unpainted Brembo Caliper Pair - 34116850931/34116850932 - eBay
- M Logo Brake Caliper Stickers - eBay

Along with some of the threads:
- https://www.1addicts.com/forums/show....php?t=1685873
- https://www.e90post.com/forums/showt...+brakes&page=6
- https://www.1addicts.com/forums/show....php?t=1306682
- https://www.1addicts.com/forums/show...1132152&page=4
- https://www.1addicts.com/forums/show...=658932&page=3
- https://f15.bimmerpost.com/forums/sh....php?t=1527339
- https://www.1addicts.com/forums/show....php?t=1376789
- https://www.turnermotorsport.com/t-b...ke-Differences

Here are a couple pictures of the front and rear calipers when I got them from eBay:





I also wanted to go for some extra flair with the upgrade and I kinda wanted to copy Suprgnat's brake setup (https://www.1addicts.com/forums/show...&postcount=247) since their car has been a pretty big inspiration for me. My goal was to get my front and rear calipers powdercoated in Phoenix Yellow to emulate the BMW Performance Brake kit.

Getting the calipers ready for paint was actually one of the most frustrating things I've ever done though. I watched videos and read threads to mentally prep myself, and I don't know if it's just me, but whenever I have to use a new tool for the first time I swear my IQ goes into the negatives. I fumbled around with getting everything attached to the air compressor I bought from harbor freight for longer than I'd like to admit, and then once it was time to start popping the pistons out of the calipers, I was in the trenches.

The rear calipers weren't bad at all. The fronts took years off my life.

I don't know how many times I'd pop 1 or 2 pistons out, just for me to need to push them back in so I could try to push the others out. The first caliper took the longest because my technique was horrendous. I also could've saved a ton of time by not being lazy and just buying another piece of wood that was sized properly to allow the pistons to be pushed out enough for them all to evenly be pulled out, but since I was able to get 1 piece of scrap wood from Home Depot for free, my inner Mr Krabs forced me into using random things from the garage to try and stop the pistons from getting pushed out too far. Once I had my technique dialed in, I knocked out the second caliper quickly, but that's when disaster struck.

Picture this - you've just had a great Sunday. You've successfully broken down 2 rear calipers and 1 front caliper. Your favorite football team just won, and your favorite F1 driver just had a great race. You're not doing any extra work on the weekend to get ahead at work for once. You're dreaming about how sick your new brakes are gonna look on your car. Life is good. You decide to wake up early before work to break down the last caliper so you can get it over to the powdercoating shop before you have to be in the office because what better way to start the week than with a huge W in the morning? You go out to the garage and get to work. Pistons all pop out easy. You don't even have to reinsert one that popped out prematurely. Dust seals all come out easy. Left side bleed screw comes off no problem. Right side bleed scre—





Devastation.

My immediate thought was like there's no way. There's absolutely no way this happens to me right at the finish line. I'm not even sad in the same way I was when the radiator hose snapped at the finish line. I was just dumbfounded. Instead of starting my week like a king, I went into the office like a chump and all I could think about was how I could get this broken bleed screw out of my caliper.

After work, I bought an extractor, but I wasn't hopeful since I had read a few posts of people trying to use extractors on bleed screws and ultimately needing to buy a new caliper anyway. I spent a decent amount of time trying to get the bleed screw out, but my drill wouldn't grip the extractor when it was time to reverse it out of the caliper. Even after taking a break and trying to use heat + more penetrant, the bleed screw still wouldn't move.



The next morning, I went and bought a tap handle since I had seen recommendations to use one of those. I bought the only one Home Depot had, and it was lowkey, but highkey expensive since it was part of some Milwaukee tap an die set and promptly proceeded to break my extractor inside of the bleed screw while trying to twist it out. Sick.





I couldn't find any machine shops near me when I searched for them, but there was an engine shop not too far from me, so I called them just to see if they could remove the bleed screw for me or could at least point me in the right direction. The guy on the phone told me that it wasn't worth it since there's no guarantee the screw would come out without the threads on the caliper also being damaged, and with the costs a shop would charge combined with the amount of time they'd have the caliper he recommended for me to buy a new caliper and said that's what he would do for his own car.

So after I got off the phone with him, I held my head in shame, said a quick prayer for my wallet, busted out my credit card and another eBay F30 caliper was on its way from SC. This one was completely blank, compared to having the BMW logo stamped on to the side like the first pair, but everything else seemed to be the same.



It only took a day to arrive, and I tried loosening both bleed screws before I even attempted to wrestle with the pistons again. Once the bleed screws loosened easily, I broke the caliper down like a pro since it was my third time. From here, the calipers were ready to take to the shop.

I followed this thread https://www.e90post.com/forums/showthread.php?t=1473695 and asked the shop to use Schneiderwyzen PMB-7081 from Prismatic Powders and was extremely happy with the results.







Reassembly was easier than disassembly but still was pretty tedious. I've never gotten anything powdercoated before, so I don't know if the shop didn't do as well as they should have with blocking all the threads on the caliper, or if this was just the nature of getting brakes powdercoated, but the first thread of every screw hole on all 4 calipers had just enough powdercoat in them to where threading in the brake lines and caliper carrier bolts was impossible until I had scraped away paint for the threads to catch properly. I don't think using a pick was the best tool for the job, and there probably was something better I could've done, but this cost me a ton of time.

Putting all the seals and dust boots also was pretty time consuming. For the front calipers, the pistons inside the new dust boots wouldn't push all the way down easily by hand. They'd go in about 75% of the way with no effort, but once they caught the inner dust seal I couldn't push them down by hand. I had a friend with me and we both tried to push with no luck. Just to sanity check and ensure the pistons weren't going in crooked, we completely broke down one of the calipers to see if we had scratched any of the walls of the caliper and everything was fine. To get the pistons to fully seat into place, we ended up using an old brake pad with a c clamp to push them down. Since I was nervous because every thing that I've read and seen in videos said that the pistons should pop back in easily by hand, I put air back on the calipers to try and slowly press out the pistons to see if they moved easily, and they weren't stuck or anything and they did. From here I was able to push them back down without needing to use the c clamp.

For the rears, getting the outer dust boot to seat all the way down on the caliper body was the hardest thing for me. I tried for a long time to get the dust boot flush, but one side would always be slightly away from the body. After spending 6+ hours on getting them to sit properly. I decided that I would go with what I have and try to make more progress and see if they caused me issues in the future.



Moving on to the installation of the brakes, installing the front rotors, pads and calipers wasn't much of an issue. My friend and I did the passenger front together since I'd never done anything with brakes and he had the experience, then I did the driver's front and the rears on my own over the next few days.







My rear rotors were stuck pretty good. I was able to get my driver's rear off with the 2lb dead blow I already had after a good amount of time hitting the rotor, but after listening to my hammer whisper sweet nothings into the ears of my passenger rear rotor for a long time, I finally decided to override Mr Krabs and to go back to harbor freight and get a larger hammer. I bought a 5lb and a few minutes after getting back home my rotor was on the ground.







I got the caliper reinstalled and was happy to finally be done with the first part of the job. The master cylinder + bleeding the abs pump and brakes + reinstalling my rear caliper clips (left off because I hate removing them and I still feel like I did something wrong and will need to remove my rears) were still left to do.

Just like with the suspension, since I'm doing everything for the first time, I expected things to take a long time and to face hiccups, but instead of trying to rush, I've been going slow and working on the car after work and on the weekends. If I have a late work day and I'm tired, I'll rest or friends want to hang out I prioritize them over the car. However with my slow pace and some things keeping me from working on the car like I'd want to, it's now been 3 weeks since my car first got on stands and I've been itching to drive bad, so I'm going to try my hardest to at least have the car on the ground again by the end of the weekend.

I also feel like I'm in my head some, but the work for the brakes has had me the most nervous out of all the jobs I've done on the car so far. Everything seems relatively simple, but since they're my brakes I don't want them to have issues, and I feel that with my rebuild experience not matching what I've seen in videos or read about in threads that I've done something wrong. At this point all that's left is to get back to work and just be extra thorough when bleeding and testing my brakes to make sure I don't have any leaks or sticking pistons.

If you read this before I finish changing everything, wish me luck because I really hope my next update doesn't include any hiccups with the master cylinder or the brake bleeding process

[C-R12]

We're back on the ground!

Changing the master cylinder wasn't nearly as bad as I thought it would be. The job was pretty straightforward and I followed this video: 328i Master Cylinder Install. One thing that was interesting was that my MC reservoir had a braided hose attached, but I couldn't find any information on what it could be. Realoem doesn't list it, and I couldn't find any other uses of it in other pictures and videos. My only guess is that it's related to the clutch in some way since I can't think of anything else that would connect to the MC.



The 328i MC (bottom MC) wasn't visually any different from the 128i MC other than it had 25 stamped on to the body compared to 23 on the 128i one. I replaced the grommets and the o-ring on the 328i MC as well. The new ones weren't very different from the ones that were already there, but I'm sure it can't hurt to replace them anyway.





I bled the system using a power bleeder and used INPA to activate the ABS pump, and that was also easier than I expected too. Cracking open all of my bleed screws multiple times also helped get me over my fear of rebreaking a bleed screw. I got everything back together, added performance brakes to my VO, and got ready to do a test drive. I could've swore that I read somewhere that redstuff pads had a bedding procedure, but the EBC website says that they self-bed in 100-150 miles, so I didn't end up bedding them on my drive. Unfortunately, very shortly after I left my neighborhood, I got a DSC warning that ended up being a code for steering-angle sensor: plausibility (5E49). I'm not sure what I could've done to trigger that error. I had it once before when I did all of the suspension work, but after a few miles of driving after my alignment it went away. I also had low rumble/grind from what seemed to be my passenger front whenever I hit the brakes around 20-30 mph, so that cut my test short. There's no sound when I'm driving at extremely low speeds < 10mph, so maybe it's the sound of the pad rubbing the new rotor? I also read that it could be the dust shield hitting the rotor, so will check that tomorrow. I also thought it could be my wheel coming in contact with the caliper, but I haven't seen any scrapes on the caliper, and I would expect to hear a sound at all times and not just under medium speed braking. The last thing I could think to do to test is to try and get up to around 30-40mph in a parking lot and hit the brakes to see if I get any pulling or a vibration, which I think would point me to a caliper/piston issue. I had no vibrations at all while driving tonight and braking felt normal, but I'll double check again tomorrow and report back. Even with the minor issue, the calipers look so cool on the car

[C-R12]

Minor setback? After work today, I came out to check the car and my pedal was extremely soft. I was surprised since the pedal felt fine last night and I didn't notice any leaks when I bled the brakes yesterday. When I went to go lift the car up to try and investigate the noise from the passenger front, I noticed that the driver's front tire had fluid on it. I felt on the caliper and the inner bleed screw on the caliper was a little wet. Same with the passenger caliper. In terms of the rumbling noise from the passenger front, I checked the dust shield and spun the rotor manually and didn't hear any unusual noises, so the next thing to investigate would be the pads.

On the drivers front side, as I was cleaning up the caliper, I noticed that the fender liner had fluid on it, and the bottom inner lip of the caliper beneath the rotor had fluid on it too. After I dried things up, I decided to turn the car on and press the brake since the pedal was a lot softer when the car was on as I drove up my ramps compared to when the car was off. When I went back to my caliper, the bottom was slightly wet again. I decided to pull my pads to see if my pistons were leaking fluid, but from what I could tell, the pistons are fine. I ran my finger across all of them and only had brake paste on them and the back of the pads were dry too. I'm not too sure where the fluid underneath the caliper could've come from if the pistons are dry. I'm thinking that maybe the bleed screw just leaked more fluid than I had initially noticed and after I dried it up the first time it continued to run down the caliper. My MC reservoir also is at the same level as yesterday, so the leak appears to be minor, but I'll bleed the ABS and use the pressure bleeder tomorrow and go a little tighter on all my bleed screws all the way around and see if I encounter the same behavior

[tracer bullet]

Originally Posted by C-R12

I was surprised since the pedal felt fine last night and I didn't notice any leaks when I bled the brakes yesterday.

I know that feeling! The "WTH, this was fine". Maybe it's obvious but the pattern on the fender liner suggests it's getting on the tire and then being thrown, which is odd.

FWIW it seems that re-bleeding to be sure there's no air, and a good cleaning afterwards, is the right thing to do. Hopefully there was some air still trapped and if anything is leaking you can ID exactly which caliper and where.

[greywing.wip]

Awesome thread, dude. Love the detail in your process.

Also came from an e36 in college back when I had no mind & no money. This e82 is such a nice throwable toy.

[C-R12]

Originally Posted by tracer bullet

I know that feeling! The "WTH, this was fine". Maybe it's obvious but the pattern on the fender liner suggests it's getting on the tire and then being thrown, which is odd.

FWIW it seems that re-bleeding to be sure there's no air, and a good cleaning afterwards, is the right thing to do. Hopefully there was some air still trapped and if anything is leaking you can ID exactly which caliper and where.

Yeah definitely agree that it was hitting the tire and getting flung up. I ended up cleaning the wheels and re-bleeding everything yesterday and figured out that the fluid was coming from within the caliper on the driver's front, so will have to take it off and put in a new inner seal

[C-R12]

Originally Posted by grywng

Awesome thread, dude. Love the detail in your process.

Also came from an e36 in college back when I had no mind & no money. This e82 is such a nice throwable toy.

Thank you! The e82 is so much fun. My e36 was an auto, so I might've thought it was more fun if it was manual, but I think even if I had one of these in auto it'd be a lot more fun than the e36 too

[C-R12]

Went back to investigate the leak last night, and I've determined that the leak is coming from within the driver's caliper. It's pretty annoying because I re-bled the entire system just to turn the car on and have the pedal go completely limp. Fortunately, I didn't take the car fully off the stands to figure this out, but with Thanksgiving coming up, I'll have to take a break for about a week before I can come back and rebuild my caliper.









It's not easy to tell, and even in person it wasn't very clear, but after tightening all of my bleeder screws and brake lines and making sure everything was dry after the re-bleed, when I stepped on the pedal, I had pool of fluid under the caliper, and it seems like the bottom piston on the inner side of the caliper is leaking. I guess when the system was pressurized by the bleeder the caliper didn't leak, but once there wasn't something else keeping pressure the fluid escaped past the piston. I thinking this means that I rolled the inner seal whenever I first rebuilt the caliper, so my plan when I can work again will be to ideally just pull the one piston and change the seal and then reseat from there, but more than likely all of the pistons will pop out when I press them out. I may not even need to buy a new rebuild kit, but I'll change the one seal just for peace of mind.

[tracer bullet]

On the up side, you found the leak, and now you know how to get it all apart and put back together.

[ZHPizza]

Awesome thread! Love that you're documenting all of your mishaps along the way as you're admittedly learning the ropes on a lot of this stuff. There's a wealth of knowledge among the members here and we'll try to help you where we can, but it seems that you already know that the best way to learn is by jumping in and getting into a bit of trouble.

Hate that you junked a caliper with the bleed screw debacle, but that's a sort of right of passage that everyone has to go through in order to learn how delicate those screws are and develop the feel for when they're going to strip.

At this point I can zip through every fastener on a car with an impact driver with no damage done, but that capability was developed over a long history of stripped/broken fasteners - each one is a learning opportunity!

[cblock406]

Originally Posted by ZHPizza

the best way to learn is by jumping in and getting into a bit of trouble.

100% agree with this. There's no better way to learn than getting your car to the point of no return, where the car isn't moving out of the garage until you figure out how to fix it.

Awesome thread and love where you are taking things. Those Apex wheels look great.

[C-R12]

Originally Posted by tracer bullet

On the up side, you found the leak, and now you know how to get it all apart and put back together.

Yup exactly and now the idea of rebuilding the caliper isn't some unfathomable task like I thought it was a few months ago, so that has been one benefit of doing things myself and messing up. I can't wait to get back home and work on the car because I've been itching to drive it again. The Sonata just isn't the same at all lol

[C-R12]

Originally Posted by ZHPizza

Awesome thread! Love that you're documenting all of your mishaps along the way as you're admittedly learning the ropes on a lot of this stuff. There's a wealth of knowledge among the members here and we'll try to help you where we can, but it seems that you already know that the best way to learn is by jumping in and getting into a bit of trouble.

Hate that you junked a caliper with the bleed screw debacle, but that's a sort of right of passage that everyone has to go through in order to learn how delicate those screws are and develop the feel for when they're going to strip.

At this point I can zip through every fastener on a car with an impact driver with no damage done, but that capability was developed over a long history of stripped/broken fasteners - each one is a learning opportunity!

Thank you! The knowledge here has been so helpful because I started at basically level 0, but following the guides and learning from other people's past experiences has made all of this possible. I still have the caliper sitting in the garage so maybe one day I'll be able to figure out how to bring it back from the dead. Yeah I agree that messing stuff up is the best way to learn how to not mess things up lol so here's to hoping that I'll be following in your footsteps very soon

[C-R12]

Originally Posted by cblock406

100% agree with this. There's no better way to learn than getting your car to the point of no return, where the car isn't moving out of the garage until you figure out how to fix it.

Awesome thread and love where you are taking things. Those Apex wheels look great.

Ayeee appreciate the compliment on the wheels and the thread! I agree let's just hope the next time it comes out of my driveway it's not on a tow truck

[C-R12]

Was finally able to work on the car again, and I've found the piston that wasn't holding pressure properly. My set up was a little goofy, but to diagnose which piston was leaking, I removed my caliper and placed a piece of wood between all the pistons. I then pressed on the brake pedal until the pistons contacted the wood, and I could see which piston was leaking fluid.



Even before the piston started leaking from the caliper, I could tell that the piston wasn't seated properly because it pushed out from the caliper a lot easier compared to the other pistons. Once the piston contacted the wood and couldn't slide any further, it leaked a ton of fluid.



When I removed the wood from between the pistons, I tried to see if I could wiggle the leaky piston since from my past experience, the piece of wood that I have is thick enough to where the pistons can't immediately be removed until I use a thinner piece to stair-step them out of the caliper. I was surprised to find that the piston could rock back and forth and was even more surprised when as I went to remove the caliper from the car, the piston fell out on its own once I lifted the caliper.

From what I could tell, the inner seal looked normal and the piston looked normal, so I'm not too sure what could've gone wrong.







My mind loves to go to absolute worst case scenario and I started thinking that maybe the caliper bore for the piston was slightly too wide, but I feel like the odds of that are so low. I didn't want to work too late since I was feeling tired, and I've learned my lesson from working while tired, so my plan for tomorrow is to replace the inner seal and the dust boot and to swap the current piston with one of the extra ones from the caliper with the stripped bleed screw and hopefully we're holding pressure

[C-R12]

I did more debugging and was able to isolate the issue. After replacing the seal for the one leaking piston, I went to go test the brakes while still on the stands again, and I still leaked fluid all over the floor. I started stressing because I couldn't tell where the leak was coming from and I was sure that the one piston would be the solution. I ended up taking a break for a few days to try and think over all the things I'd done to find the leak. I came up with an idea to try and stick shop towels between the pistons and the pads to see if fluid would hit the towels while I pressed the brakes, and I would use the indentations from the pistons to determine which one wasn't holding pressure.







From the testing I could see that one of the inner pistons had a slight fluid leak, but it wasn't consistent. However, the floor under the caliper still would get soaked. I had a friend come over to help me look at things since I figured having another person to help me look at things would be helpful, and we would at least be able to look at the caliper while someone else was on the brakes. I changed the seal on the one piston that had the slight fluid leak, and we still had a leak from the center of the caliper, which my friend was able to see while we were testing. I was ready to buy another caliper at this point since I figured a leak at the seam would be a caliper defect, but before I went to spend more money, we did more research and realized that there's a crossover seal in between both halves of the caliper and if it's not sealing properly, you can get leaks down the middle.

Since I was prepared to buy another caliper in the worst case and was committed to driving around with one painted and one unpainted caliper for the short term just so I could drive again, I figured if I split the caliper and had further issues, I wouldn't really lose anything, but if I split it and the seal was the issue, then I would save myself a ton of money. I followed this post: https://f30.bimmerpost.com/forums/sh...php?p=32176199 and some other youtube videos that weren't bmw brembo specific and quickly found the issue.









The threads of the caliper screws on the side of the caliper with the crossover seal were wet compared to the ones on the other side, and the same was true for the halves of the calipers. The side with the seal was wet on the faces, while the other side was completely dry. The seal had deformed, which I'm almost certain came from the powdercoating process. The powdercoater had told me that I needed to remove all seals since the oven would ruin them, and since I had overlooked the crossover seal, I caused myself issues. It was a little annoying that I did so much research but still fumbled and missed such a crucial detail. I remember wondering what the tiny seals inside the bimmerworld rebuild kits were for, but I'm glad that I've gotten into the habit of not throwing anything away while working on projects until I'm sure they're completely done, because it would've been even more annoying to have to order more parts because I threw them away on accident. Changing the seal resolved my issue immediately.

The following day, I replaced the seal on the passenger side caliper as well, since even though it wasn't leaking as badly, it also got put in the same oven, so it only makes sense that the seal probably wasn't in as good of shape as a new one.



The passenger one had some hairline cracks in it, so I'm glad I replaced it too. I was able to put the wheels back on and finally pull the bmw off IR and open up the 21 day practice window. I did a test drive with some hard stops and had no warnings or leaks inside the barrels of the wheels. I really like how the car stops now too. I think the caliper saga is finally over, but I'll do a few more quick trips before I report back on how everything is going