i'm working on a 2006 R53 that i just bought. the parking brake doesn't hold the car in place properly. so, before i go much further i'm soliciting input.

i lifted up the rear end and took off one of the tires. what i found was that when you pull up the parking brake lever, the driver side cable pulls down significantly more than the passenger side. however, the passenger side holds the wheel tightly while the driver side does very little.

restated:
driver side - cable pulls more - less stopping power
passenger side - cable pulls less - more stopping power

i don't think it's a parking brake cable itself because the parking brake lever on the caliper is depressing more. that said, i'm looking at culprits outside of adjusting or replacing the parking brake cables.

i'm kind of wondering if it could be the caliper itself, but i don't know enough of how this car's braking system works. is there something internal that could fail for the parking brake?

the other thought i had was to bleed the brakes. the brake pedal is a bit soft and i was already thinking it might need to bleed them. however, i don't know how the caliper on this works. if the parking brake is mechanical, i would think it would work regardless of any air in the lines.

that's where i'm at. any thoughts or insight?

 

 

My apologies in advance for I don't have an answer or experience for the right fix.
I can only share one incident which occurred many years ago when we had an indie garage (non BMW) replace the rear brakes on my 2004 R53.
The mechanic had improperly preformed the brake pad replacement by not dialing back the rear calipers as required. I had moved (from FL = flat terrain), to another state (a mountainous region) just a few days later only to discover I had no Ebrake.
I located a Mini dealership in the area and had to have the calipers replaced due to damage caused by the improper brake pad replacement procedure....at a ($tealer$hip) cost of $1,100.
I don't know enough to suggest that this may be your problem.

Since then I've purchased the proper brake/caliper kit and have been replacing and servicing my own brakes without a problem.
Perhaps it might be a stuck piston/caliper?

 

The mechanical parking brake mechanism in the caliper can seize up. I've had to replace countless numbers of rear calipers in my cars (many makes, including MINI) over the years because the parking brake mechanism froze up. I've also had to replace the parking brake cables on my son's R50. I lived in heavy snow (and road salt) areas.

Your brake calipers don't look very corroded, especially the drivers side. The passenger side parking brake mechanism in the caliper could be partially seize and it does look older than the driver's side. It could also be one of the cables that is corroded and not moving smoothly.

There is a balancing mechanism (circled in red in the image below) just behind the parking brake lever. Both parking brake cables attach to it and it pivots freely. It might be worthwhile looking at that to see what it's doing when you pull the brake lever. My guess is that both cables aren't moving equally. Start by investigating the side that isn't moving. My guess is that the problem is with the passenger side caliper or cable. Because the passenger side isn't moving the full range the driver's side is moving more, but the driver's side can't move enough, because the passenger side won't let it, to tighten the cable and therefore the brake. I hope that is a clear explanation.

You access this mechanism from above. I think you need to remove the center trim around the parking brake to get at it. Its been a while since I serviced my sons.

Also check to see if the passenger side brake/rotor gets warmer than the driver's side after driving and braking some. This would indicate that the parking brake isn't fully releasing, either due to the caliper or the cable not moving freely.

Also make sure the calipers are sliding freely on the guide pins. My son's car built up a thick white corrosion under the rubber boots and the guide pins wouldn't allow the caliper to move to apply equal pressure on each brake pad. Uneven wear between the pads would be an indication the calipers aren't sliding freely on the pins.

 

i appreciate the input.

the passenger side is working properly as i cannot spin the wheel when the parking brake is on and is free when the brake is off.

the driver side, i actually pulled the cable out of its normal location and propped it up on top of that bracket to get a little more leverage, poorly illustrated below. it still didn't tighten up.





i have not pulled the passenger wheel, but i could still see the brake pads a little bit. driver to passenger side, they look to be worn fairly evenly (as much as i could eyeball) and are close to needing to be replaced. you can see how little material is left on the driver side if you look at the pics. all of the cars that i've had for extended periods of time are rear drums. all of the rear disc brakes have been newer and i kept them shorter - so i've never had to deal with a failed parking brake on a disc brake car before.


i guess i'm getting somewhat tripped up mentally of the concept of the mechanical parking brake failing inside the hydraulic caliper. but, having slept on it and reading y'all's responses, i'm kinda honing in on a potential caliper failure on the driver side. what i do not enjoy doing is throwing parts at a problem. i'm more into diagnosing first.

 

Most of the time the cables will rust or stick and not retract. The other cases are the piston itself on the caliper will stick and the spring back will not pull back tension on the cable. Mine had so many miles i just replaced both calipers with ATE brand. We have bremmen parts also.

https://www.northamericanmotoring.co...in-an-r53.html

Rear calipers:

https://www.ecstuning.com/Search/Sit...h/34216763729/
https://www.ecstuning.com/Search/Sit...h/34216763730/

 

Well... It's definitely the caliper. I did a little bit e testing today. I can activate the parking brake by hand on the passenger side enough to stop the wheel. On the driver side, I can pull the lever and see the piston move slightly. That was when I noticed the problem... The piston doesn't push the pad into contact with the rotor. And with someone inside the car pushing the brakes, the piston kinda tries to come out but not much. See the picture below.

So, new caliper time. And, I'll be doing the rotors and pads, too, because they're on their last legs. That's not an expense I wanted to face as I've run out of money getting this car put back together. But I gotta have brakes. The worst part is bleeding them. My God have a lost my patience with bleeding brakes. Hahaha.....

 

Sounds like you've gone through a process to identify the problem. I've never seen a failure like that. Just seized mechanisms and cables from corrosion of living in the salty north.

FYI - Here's a video of a rear caliper with integral parking brake. It's European and should be similar to the MINI caliper. You can get an idea of what's inside if you're interested. You'll notice that the person moves the parking brake lever and the piston moves.

 

well, long story short - it was the caliper. i replaced the caliper and did new pads/rotors. after bleeding the brakes the parking brake works perfectly. and the car stops way better w/4 wheels braking instead of 3.



wagner pads and durago rotors plus a new caliper from @ECSTuning




give the rotor a little tapa-tapa to separate from the hub...




and done. (i remembered the caliper spring later)

 

Late to the party but the same thing happened on my R53 and it wouldn't pass state inspection here in Texas (has to hold the car up to 1,200rpms). Ended up being a seized caliper piston. A $50 Frenkit rebuild kit (comes with new piston) solved the problem (easy install).