Electrically operated parking brake.

[t-tony]

I hax to fit some rear brake pads on our Abbie's Audi A3 today. It is fitted with an electrically operated parking brake (like my E89 Z4) so I had to come up with a way to retract the calliper pistons.
What I ended up doing was to use my Snap-On power probe running from a 12v battery on my bench.

I also used a pair of large water pump pliers.

All.you need to do is un plug the wiring connector from the calliper. Then attach the Croc clips on the power probe to the battery terminals (do NOT connect anything to the cable plug).
Attach the small black fly lead to one of the pins on the calliper, then touch the probe tip to the other pin and press the feed button. You should hear the motor run. Allow a few seconds then stop. Using the large w/p pliers see if the piston will press back in. If it does repeat until it is fully in. If the piston pushes further out simply swap the connections on the calliper pins and retry.
Once you have reassembled the calliper and pads pump the pistons out. Then lastly re connect the calliper electrical connectors.
The power probe has an "overload" protection button so you can't hurt anything.
And yes I know the Z3, E85 Z4 don't have this type of parking brake, but, the E89 does and most likely the G29 does too.
Brembo pads haven't half shot up in price too.

Tony.

 

[Jack Ratt]

Good bit of brain work there mate

 

[t-tony]

Just using stuff I already had Garry.

Tony.

 

[Alan Slade]

I had a similar problem with the electric parking brake on my son’s Audi A4. I got over it by using a piston push back tool, tighten it with the parking brake off, then put the brake on and release it, you then get a gap, tighten the tool again and repeat again and again until the piston is retracted. Not very technical but it worked.
My Citroen C4 was easier, just take the actuator off two bolts and wind it back using a torx in the centre.

 

[Ianmc]

Why invent an electric parking brake? Something else to go wrong, madness.

 

[Pingu]

Why invent an electric parking brake? Something else to go wrong, madness.

It saves a few seconds (possibly over a minute) to fit at the factory.
(Cable to fit + Brakes to adjust) v. (Plug caliper into wiring loom)
From a production engineer's point of view it's a no-brainer

From a mechanical engineer's point of view, there are many things wrong with it. The worst is the safety issues.
I've had two dangerous problems with mine...

1. The brake power relaxes over time. You can see the force dropping on the diagnostics. It has relaxed so much that the vehicle started to move. Luckily, I was in it, so I was able to reapply the brake. This is probaly why you can;t take the key out unless you are in P.
2. The handbrake disengages when you apply the throttle if the vehicle is in gear. I thought I was in N, but was in R, and blipped the throttle to stop a rattle, brake came off and vehicle started to move. Operator error, but wouldn't have happened with a cable.

 

[Nodzed]

Couldn't really give a hoot whether its electric or manual but the e89 parking brake working off the calliper is a god send compared to the Z3 Z4 e85 handbrake system, which is crap.

 

[Nodzed]

My Citroen C4 was easier, just take the actuator off two bolts and wind it back using a torx in the centre.

e89 can be done the same Alan.

@t-tony
Tony I would be interested if the e89 can be wound out the same way?

 

[colb]

Electronics are a nightmare on modern cars when they go wrong and diagnostics are not that great in pinpointing what's gone wrong often leading you in the wrong direction unless you know what the diagnostics is really trying to tell you what's gone wrong. Give me the old distributor with a set of points and a coil and a carburettor maybe an electronic upgrade to the points any day over all this modern module for this and module for that. Will be avoiding an Electric vehicle for as long as possible total reliance for everything on electricity doesn't bode well for me and range they have is of no use to me.

 

[t-tony]

e89 can be done the same Alan.

@t-tony
Tony I would be interested if the e89 can be wound out the same way?

Yes, it can Niall. Just swap the connections on the pins in the calliper. I found that out as the handles of the waterpump pliers started to spread!

Tony.