Catch 22 (EPB)

[spitz]

On attempting to drive off from my drive a few days ago I found the car stuck solid with the parking brake refusing to disengage, despite numerous pull/push attempts on the lever under the dash.

I also had two messages appear on the dash, ‘Park Brake not fully released’ and ‘Parking Brake Service Required’.

I was able to determine that it is the near side calliper with the issue just by listening for the motor activating while my wife applied/released the brake (offside sounded fine, near side silent).

I tried to release the brake on the offending calliper using the 9v battery method seen in a few YouTube videos. Doing this I was able to get the motor to operate, but not in a way that released the brake. It also sounded ‘rough’.

The only option I think left to me to be able to move the car was to manually remove the EPB motor (to gain access to the winding mechanism behind the pad) by undoing the two T30 torx bolts. However, to do that I have to remove the whole caliper as otherwise the top bolt is inaccessible. I can’t remove the calliper as the parking brake is locked on, hence the title of this post.

If you have read this far, thank you and if you can offer any help or advice thank you even more.

My car is a 2012 V70 with 91k miles. My car has had a recent full service at an independent Volvo specialist with all belts changed plus replacement of both rear trailing arm bushes.

[TeamG]

Are you able to remove the brake disc and the caliper together, then access the torx bolts? Removing the torx bolts requires a long torx bit, as the centre of the torx bolts is very close to the motor. Without this, you risk breaking the plastic tabs on the motor housing. Try a multimeter on the end of the EPB connector (car end) then operate the EPB lever and see if the voltages are sensible. If that works, it’s either the motor or EPB within the caliper that is seized or sticky.

If you find the motor is fubar, I found that replacing the caliper with motor attached was cheaper than sourcing a motor alone. Ebay is your friend, I picked one up for around £70-80.

[apersson850]

Originally Posted by spitz

Doing this I was able to get the motor to operate, but not in a way that released the brake. It also sounded ‘rough’.

Some cars suffer from rust on the motor axle. Since the splines are equivalent to XZN 8, it doesn't take much rust for them to disappear, in which case the motor will no longer turn the little jack that applies the parking brake.

If the motor is toast and hopelessly lost anyway, you do have the option to hammer it off. As the ears used to hold it in place are plastic, that's perfectly doable.

[spitz]

Thanks TeamG and appersson850 (our first Volvo was an 850 and it’s been estates ever since) fir your replies.

Removing the whole assembly I hadn’t thought of and is certainly something I will try if I can’t get access to that second bolt on the motor (I’m borrowing a long torx bit from my son today to see if I can access it with that).

I was reluctant to do any multimeter testing with the motor lead disconnected as I had read this could cause other problems (ECU ?).

My primary goal is to get the parking brake released so I can take the car to a specialist to have it checked with VIDA and the motor confirmed as being u/s. In this case I would then get a quote for a replacement.

[SnineT]

Originally Posted by spitz

Thanks TeamG and appersson850 (our first Volvo was an 850 and it’s been estates ever since) fir your replies.

Removing the whole assembly I hadn’t thought of and is certainly something I will try if I can’t get access to that second bolt on the motor (I’m borrowing a long torx bit from my son today to see if I can access it with that).

I was reluctant to do any multimeter testing with the motor lead disconnected as I had read this could cause other problems (ECU ?).

My primary goal is to get the parking brake released so I can take the car to a specialist to have it checked with VIDA and the motor confirmed as being u/s. In this case I would then get a quote for a replacement.

If you haven't already I'd attempt to wind them off into the service position through an OBD reader that has that function, if that fails do what Ap said above, the VW ones were terrible for cracking the plastic housing and letting water in so some looking on their forums might also help you avoid the pitfalls of disassembly as they are probably almost identical in their construction.

[spitz]

Originally Posted by SnineT

If you haven't already I'd attempt to wind them off into the service position through an OBD reader that has that function

I’ll look into that. My son has an OBD plug that I can try. Thanks SnineT

[spitz]

Update: Managed to get the EPB motor off without dismantling the rest of the caliper. A longer T30 Torx bit did the truck.

Looks like the motor drive shaft has rusted to the point where it was no longer engaging with the caliper. I was able to wind back the brake pad with a T40 Torx so that the wheel now spins freely.

Next to find a replacement motor. Does anyone know if it has to be coded to the car or will any motor from an equivalent make and model do?

[SnineT]

You'll need a Volvo one, I wouldn't imagine it needs coding in though however it might need setting with the OBD I mentioned earlier so the pair are balanced etc.


If you're stuck have a look on You Tube for others who've replaced the pads using the 5v battery method rather than a tool, this should help you set them equal when you put it back together, I'd imagine you'll need to fully retract the working one before doing so though.

[monkeh]

As above, as long as you set the motor to how the other one is set, you should be good.

I.E. Both wound out, with battery, then wound back in with battery so they're both "matched".

You may get a serving parking brake message once or twice until it figures out the motor positions.
It's happened to me when changing pads, but forgetting about leccy brakes in the summer after I'd had a few beers made me realise my mistake. Mini 12v pack to engage the pair of them... Golden.
(work on private ground so beer is permitted &#128521)

[apersson850]

Inside the caliper, there's the common hydraulic piston for the normal brakes.
Then there's a small mechanical jack, driven by the motor, to apply the parking brake. The two are in series, so hydraulic cylinder kind of sits on the mechanical one.
As the pads get worn, the mechanical little jack has to accomodate. The parking brake runs the motor for a certain time, or until the current gets so high that it's obvious that it has pushed the piston far enough for the parking brake to be engaged. If the time runs out before the current goes up, an error code is stored, since the system thinks that the parking brake can't be applied properly.
When you release the parking brake, it simply runs backwards for a certain time.

This means that if you put in new pads, you need to crank that jack all the way back, to allow you to push the piston in all the way too. Or you can't get the caliper to grip over the new, thick pads.
If you put back used pads, you want the parking brake to be out to the correct position, to avoid the error code.

If you remove the caliper, run the motor back (or remove it and wind the jack back mechanically), then put in used pads and just put the thing back together, you may have to apply the parking brake several times before it engages. Then you get the error code.

The option you have is either to the parking brake after putting the caliper together without using the parking brake on the car. Like with that little battery. Or you can do this (assuming you have pushed the piston back when you had the caliper off):

1. Place the caliper over the used pads.
2. Press the brake pedal multiple times, until it stops sinking.
3. Lift up the caliper.
4. Hand crank the jack until you feel that it hits the back of the piston. Now the jack is just behind the piston, ready to engage.
5. Put the parking brake motor back.
6. Place the caliper in place and put the screws in to complete the operation.