[phineline007]

Car:2015 BMW M235i 6spd (70K miles)

Background: I was driving down the highway and about 25 mins into my drive I noticed a vibration coming from the rear of the car. No warning lights were on and nothing other than the small vibration seemed out of place. I drove a couple more mins when the vibration got to a point where I figured I better pull off. When I got off the highway and came to a stop I got out and saw both rear rotors glowing orange. Shortly after that I heard a hissing noise (What I believe to be the brake line failing) and a bunch of smoke from the rear wheel wells.

Once I got back in the car to move it somewhere safe I noticed the brake pedal had lost pressure and all the brake fluid was out of the reservoir.

Had car towed to a shop where I was quoted $4K for new rotors, brakes, calipers. The cause they said was a failed brake line causing brakes to seize up. This is the opposite of the order of events and I had pressure till after the line broke.

Any suggestions to the cause of the problem would be helpful as I was not given a reason for failure just parts to replace without resolving the cause of the failure.

New to this platform. Appreciate any insight!

[Kernel Kurtz]

From previous posters who have had this problem usually it is caused by the parking brakes.

[Nickies]

When is the last time you had a brake flush and a full brake inspection?

[MarcoZandrini]

$4k! Find another shop. Try www.bimrs.org.

[phineline007]

Originally Posted by Kernel Kurtz

From previous posters who have had this problem usually it is caused by the parking brakes.

So you are saying the parking brake could have been stuck and there was no warning on the dash? Would that get both rotors hot enough to make them be completely orange?

[phineline007]

Originally Posted by Nickies

When is the last time you had a brake flush and a full brake inspection?

Got the car a few months ago at 60k miles. Previously owned by a mechanic. Didn’t get around to a full fluid flush yet.

[freakystyly]

Originally Posted by phineline007

So you are saying the parking brake could have been stuck and there was no warning on the dash? Would that get both rotors hot enough to make them be completely orange?

Doubt it's parking brake related. As far as I know it is only on the passenger side rear and only uses the inner hub like a drum brake, not the rotor surface.

Calipers can definitely seize but it's rare for both at the same time in a short period like that... I'm thinking it's more along the lines of brake line, fluid or maybe even ABS pump?

[Apo Zubulthums]

Originally Posted by freakystyly

Doubt it's parking brake related. As far as I know it is only on the passenger side rear and only uses the inner hub like a drum brake, not the rotor surface.

Calipers can definitely seize but it's rare for both at the same time in a short period like that... I'm thinking it's more along the lines of brake line, fluid or maybe even ABS pump?

I would bet on ABS pump.

[Kernel Kurtz]

Originally Posted by freakystyly

Doubt it's parking brake related. As far as I know it is only on the passenger side rear and only uses the inner hub like a drum brake, not the rotor surface.

Calipers can definitely seize but it's rare for both at the same time in a short period like that... I'm thinking it's more along the lines of brake line, fluid or maybe even ABS pump?

It does use the inner hubs, definitely on both sides as you can see from various adjustment tutorials.

Here is a recent related thread;

https://www.2addicts.com/forums/show....php?t=1692014

The system is completely mechanical, so more prone to problems than the hydraulics. ABS pump would be my second guess though.

[XutvJet]

Seems odd that a parking brake pad that engages the inside of the rotor hub would make the main rotor body glow. The parking brake pads are tiny and would die a quick death if they weren't released.

Both rear rotors to get stuck at the same time is really strange and I can't say I've ever read of such a thing happening on a F series car in my 8 years of being on the F2x and F3x forums. I don't see how a failed brake line would impact both rotors. It sounds serious and replacing the brake lines, calipers, rotors, and pads likely isn't going to address the underlying issue.

If it were me, I'd replace all those parts myself for WAY cheaper than $4k with a set of used calipers ($400-500) and new OEM rotors ($380), main pads ($120), parking brake pads ($60), two new brake hoses ($120), and a fluid flush ($100). Then I'd drive or tow the car to a shop or BMW to run a dialogistic on the ABS system. The hardest part of this entire job is the brake flush but even that is easy if you have a Motive power bleeder.

[phineline007]

Originally Posted by XutvJet

Seems odd that a parking brake pad that engages the inside of the hub would make the main rotor glow. The parking brake pads are tiny.

Both rear rotors to get stuck at the same time is really strange and I can't say I've ever read of such a thing happening on a F series car in my 8 years of being on the F2x and F3x forums. It sounds serious.

Just spoke with mechanic and he thinks the brake lines failed internally and the right rear line burst. The left rear caliper was siezed up but he was able to release it and a bunch of fluid came out. This makes him think there was an internal line failure and the backpressure kept the brakes engaged.

Also I have thought about the hill assist and master cylinder being a potential cause? What are your thoughts there?

[Kernel Kurtz]

Originally Posted by XutvJet

Seems odd that a parking brake pad that engages the inside of the rotor hub would make the main rotor body glow. The parking brake pads are tiny and would die a quick death if they weren't released.

Drum brakes will get glowing hot faster than disc brakes. They are not designed to dissipate the heat as well.

[Shovelman]

My guess is that the rear brakes were dragging due to brake fluid pressure in just the rear circuit. That points to the master cylinder or ABS. The hiss was the brake fluid boiling after the main damage was done.

$4,000 seems a little high but if it gets done right you'll be able to forget the sting. But you may need to fix something upstream also.

[cooolone2]

$4k for a Brake Replacement...

Welcome to BMW! Bring My Wallet!!!

As noted though, brakes are easy, it's just parts. And seeing as your system completely emptied, you'll need to have it filled correctly, tested, etc. I would change all the hard parts as noted, new flex lines as well being as the system is empty, Stainless Steel all around! Then tow it to the local dealer and let them fill and test it. Cheapest way out. Unless you have more tools or a friend who does. But you can do what you can do and soften the impact of the failure!

Good Luck

[dradernh]

Have 2 Series' $2K brake jobs (already an outrageous price) really doubled to $4K? I doubt it.