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Author Topic: Out of adjustment rear brake shoes can damage park brake actuator.  (Read 691 times)

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March 09, 2017, 08:36:19 PM

martin33100

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Just thought I should post this info up, just had our park brake actuator fault up.
I stripped the unit and it turns out as our rear shoes needed to have the slack adjusted up it allowed the actuator motor to wind all the way in and jam up.
The actuator has a load cell inside connected to the cables that stops the motor winding on the cables when it reaches a set value, as my rear shoes were worn/ out of adjustment the motor wound right up before the load cell cut the power.
With the rear shoes adjusted the motor stopped with about 10-15mm thread left on the pull rod.

March 09, 2017, 09:07:11 PM
Reply #1

X5Sport

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Re: Out of adjustment rear brake shoes can damage park brake actuator.
« Reply #1 on: March 09, 2017, 09:07:11 PM »
How many thousand miles on the car?  Just to give an idea of when to expect them to be at end of a tolerance limit?

You don't expect the parking brake to need a lot of adjustment as it should only work when stationary so wear would be minimal.  The automatic hold brake is the service brake not the parking brake after all.
:type: Never anthropomorphise computers. They hate that.

March 09, 2017, 09:36:05 PM
Reply #2

martin33100

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Re: Out of adjustment rear brake shoes can damage park brake actuator.
« Reply #2 on: March 09, 2017, 09:36:05 PM »
159k, I think the last owner may have had the rear discs changed at BMW so maybe they didn't adjust the shoes up enough.

March 09, 2017, 10:08:02 PM
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Horizon

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Re: Out of adjustment rear brake shoes can damage park brake actuator.
« Reply #3 on: March 09, 2017, 10:08:02 PM »
When I replaced my handbrake shoes on the E53 it was a PITA to adjust the rear shoes as there is so much drag in the drivetrain that you can't tell if the shoes are causing the drag or the drivetrain.
Maybe the cables stretch is a contributing factor as well. I'm sure the actuator puts more stress on the cables than a hand operated parking brake.
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March 10, 2017, 07:34:34 AM
Reply #4

martin33100

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Re: Out of adjustment rear brake shoes can damage park brake actuator.
« Reply #4 on: March 10, 2017, 07:34:34 AM »
When I replaced my handbrake shoes on the E53 it was a PITA to adjust the rear shoes as there is so much drag in the drivetrain that you can't tell if the shoes are causing the drag or the drivetrain.
Maybe the cables stretch is a contributing factor as well. I'm sure the actuator puts more stress on the cables than a hand operated parking brake.
If both rear wheels are off the ground you shouldn't feel any of the drivetrain, just the rear diff.

March 10, 2017, 07:14:06 PM
Reply #5

Nat

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Re: Out of adjustment rear brake shoes can damage park brake actuator.
« Reply #5 on: March 10, 2017, 07:14:06 PM »
Interesting..............

Every time we released the handbrake on the E70 and reversed off the drive the brakes would squeal. It would do it every time. As the car was under warranty it went to the main dealer to have it checked. Car came back with nothing wrong with it sir.
Next day same again , still squealing. Took it back a second time and said there is clearly something wrong, the shoes are clearly still binding somewhere. Again the car came back with .......all done sir , nothing wrong with the system.
next morning , guess what ? ..............like a skewered pig.

Took the car to my local indi. Explained the problem. Problem solved first time and not a squeak since.

Moral of the story ? Like the man said, check your handbrake.......oh and main dealers are shit.