Parking brake problem

[Jaykay70]

I could smell a burning smell as I slowed to park in a car park after a short drive and when I came back to the car the park logo was showing in the centre of the dash and the orange P sign is on the dash. The electronic parking brake now doesn’t work…

The brake isn’t on so there’s no binding.

I’m guessing something has burnt out…

My question is…is it safe to use? It’s still under a BMW used approved warranty but it will be a few weeks before I can take it in?

It’s an 09 E89 23i bought from a BMW dealer in Warwick a few months ago.

[B21]

No it’s not safe…you need to have a fully functioning secondary method of braking in case the primary (foot pedal) system fails…

So technically the car is in a do not drive state..

At the very least till the parking brake system is checked out by a competent person….

[flybobbie]

Electric park brake motors are not the emergency brake as such.
When i had one motor fail, i could still use the emergency function, as i tried it.
You just lose park brake function.
Good our early cars have hill start assist.

Just take it back to dealer.

[Jaykay70]

Thanks!

The car passed a BMW ACU (approved used cars) test a few months back so is under BMW warranty. It would be unusual for this to go AND the brakes to fail…plus I have no idea how you’d use the electric parking brake as a handbrake? And I’m in the motor trade! I’ve never been told that on any training course! Is there a way?

I’ve used it all afternoon without issue, the burning smell has gone…so I’m guessing the motor burnt out - I only use it every 2-4 weeks as I work abroad.

I’ll book it in for next time I’m home so I can get a loan car.

Thanks

[SV8Predator]

No it’s not safe…you need to have a fully functioning secondary method of braking in case the primary (foot pedal) system fails…
So technically the car is in a do not drive state..

What?

[B21]

Electric park brake motors are not the emergency brake as such.
When i had one motor fail, i could still use the emergency function, as i tried it.
You just lose park brake function.
Good our early cars have hill start assist.

Just take it back to dealer.

You are incorrect see posting later in this thread..

[B21]

No it’s not safe…you need to have a fully functioning secondary method of braking in case the primary (foot pedal) system fails…
So technically the car is in a do not drive state..

What?

See extract from E89 technical training manual, a short extract that clearly explains that the electronic parking brake system functions as the emergency brake..

As stated faulty parking brake equals a do not operate the car until fault diagnostics and corrections enacted..

[SV8Predator]

During dynamic emergency braking, hydraulic braking pressure is built up at all four wheel brakes.

But the hydraulic brakes have failed!

[B21]

During dynamic emergency braking, hydraulic braking pressure is built up at all four wheel brakes.

But the hydraulic brakes have failed!

The emf motor pushes directly on the back of the pad via the hydraulic piston...so no fluid required to activate rear brakes..

[flybobbie]

The emf switch operates the abs unit to apply the brakes, i tried it.
Drive along and pull lever, all four brakes come on.
Must be why there is an abs pump, that needed bleeding when i changed the master cylinder.
Reason to have four brake lines and anti skid system..

I then realised it doesn't operate the emf motors otherwise the car would skid and turn as my cars right motor had failed and P came up on the dash.
OBD said fault right motor.

Read bit on Dynamic emergency braking.

[SV8Predator]

During dynamic emergency braking, hydraulic braking pressure is built up at all four wheel brakes.

But the hydraulic brakes have failed!

The emf motor pushes directly on the back of the pad via the hydraulic piston...so no fluid required to activate rear brakes..

But, but, it was you that said "hydraulic braking pressure is built up at all four wheel brakes", and obviously that cannot happen with no fluid in the lines.

[flybobbie]

Old brake systems would have a moderator or reducing valve, so front and rear brake circuits were independently regulated.
If front or rear leaked moderator would then only allow just front or rear wheels to operate as a pair on the non leaking functioning system.

One assumes a similar set up was needed via the abs system, otherwise car would spin on asymmetric brake application..

My cars rear brake system master cylinder seals went.
Bit scary having only the fronts working.

[Pondrew]

This thread has become very confusing so I would like to condense it and make sense of the question:

According to the information posted, the 'handbrake switch' also acts as a supplementary emergency braking system if the car is moving, to stop the vehicle if the pedal fails or the driver can't use it....yes?

if the car is moving then it is only the hydraulic system which is activated by the 'handbrake switch', not the electric motors on the rears.....yes?

If I have got the above correct then the answer to the OP's question regarding the electric parking brake, as long as the button still functions in the above scenario, is yes it is fine to drive with one (or both) motors not working....yes?

How you would secure the vehicle on a hill, though, is another matter.

[flybobbie]

Leave it in gear, wheels into curb..
Bit tricky setting off if no hill assist function.

My car is daily drive so carried on driving until the new motors arrived and fitted.
Surprising how often you use the handbrake, when you realise it's not working.

[Jaykay70]

Thanks for all the answers! Used it all weekend without issue. It’s an auto and didn’t park on any hills so all good. I’ll book it in at the dealer