[Request] Instructions for replacing rear caliper

[rbtkoz]

Hi Guys, have been really utilizing all the knowledge on this site to do maintenance for my recently acquired 2013 128i SULEV with 54K miles. Good news is Carly shows no major errors.

So far I've changed the oil, oil filter, air filter, cabin filter and plugs thanks to all the posts on the site.
Pending is coolant, trans and diff fluids but logistics are hard with no reliable access to garage - apartment living in NYC.

I started on a brake flush yesterday since the car is a few months overdue and decided to investigate a banging noise I've been getting from the rear.
To my surprise, my pass side ebrake brake shoes were floating free and the bolts and springs were bent and mangled, loose in the hollow of the rotor and backing plate was a scratched up, bent and the mounting points were flared.
Thankfully I had the rebuild kit and managed to rebend the metal on the backing plate to get the new bolts and springs to seat. Ebrake needs some adjustment but holds reasonably well.

Now to my request, while in the process of flushing the brakes, I managed to snap off the bleed nipple on the rear caliper(likely because I was turning in the opposite direction).
It sheared completely flush to the caliper housing so I just ordered a reman rear pass caliper that should be here in a few days.
I am looking for instructions on how to remove and reinstall the caliper to the brake line?
Does anyone have any experience or guidance on how to approach this?
Many thanks!

[ayao]

The caliper will likely have a flexible rubber brake hose attached to it already. You will connect that to the hard line. In terms of specifics you might just need to trial-and-error the right-sized wrenches -- make sure you don't strip any of the fittings. Take a look at any BBK installation PDF - those will give you guidance on how to work with the lines.

Here's one for example: http://bd8ba3c866c8cbc330ab-7b26c6f3...Piston_BBK.pdf

[rbtkoz]

that's really useful thanks.
I just received the caliper but it does not have a hose. will have to reuse the old brake hose.

[Horigan]

First, ensure your brake reservoir is full.

The rear caliper is attached with two bolts, likely requiring an allen socket to remove from the caliper bracket. You need to also remove the hose and to do this you need a high quality flare wrench. A regular open ended wrench will likely slip and round off the hose fitting. I would break the hose loose first, then remove the two bolts that hold the caliper to the caliper bracket. Remove the wear sensor and pull out the pads. Support the removed caliper still attached to the hose while you install the pads into the new caliper. Once the you've swapped the pads, rotate the caliper to unscrew it from the hose.

Have the new caliper ready with the bleed screw open. The hard part is starting to thread the caliper on to the hose while the brake fluid is dripping out. Once started thread it all the way on, then start to mount it to the caliper bracket with the two mounting bolts. All this time brake fluid is filling the caliper and will eventually start coming out the bleed screw. Once that happens tighten the screw with your fingers and complete the installation of the caliper to the bracket.

The hose may be twisted being threaded in to a different caliper. You'll need to correct this by loosening the other end of the hose and rotate it so it you have a nice bend in the hose between the hard line and the caliper.

Bleed the brake per DIY procedures and re-install the wear sensor. A couple of pedal pumps with the bleed screw open and a hose on the bleeder to capture/direct the fluid should be sufficient.

Another option to the above is to remove the hose from the hard line, plug the hard line with a golf tee, transfer the hose and pads to the new caliper, install it, then reconnect the hose to the hardline with the bleed screw open. In fact, for a new caliper, I would use this second method. The first method works well when re-installing the same caliper, say, after replacing the seals.

[rbtkoz]

Thanks for this. I'll give this a go next weekend and report back.

[rbtkoz]

Just finished this. Was a very simple job to do.
Ordered a reman. caliper from Autozone for ~$50. Swapped out the pads and sensor. Used some brake cleaner and some brake grease and reinstalled.
Lost a bit of fluid when threading and swapping out the brake hose so followed with a pressure bleed and top up.
Pro-tip. Install the brake hose first and then the sensor cable as you need to twist the caliper to thread it into the hose, otherwise you will get it tangled.
Keep an eye on the tension of the sensor cable. If it's too tight you have to disconnect and run under the brake hose. Otherwise it will snap due to the suspension moving the wheel up and down.

Many thanks Horigan for suggesting a flare wrench for this job.