Hello,

I'm just after a bit of advice regarding replacing the electric motor part of the rear caliper which operates the parking brake. The brakes work fine when driving, but the parking brake on one side (left) is inoperable and does not engage (and last time it did it struggled to disengage, which I resolved by repeatedly engaging and disengaging parking brake until it actually worked; haven't used the parking brake since). I suspect the electric motor is seized. If I wanted to replace it, is it as easy as taking out two screws, unplugging the wire, and then simply attaching the new electric motor and plugging it in? I do not intend to replace discs or pads as part of this process. 

Are you certain the motor is seized? It is more likely that the mechanical parts of the brake linkage have seized on a twenty year old car.

When you say brake linkage do you mean the mechanical parts inside the motor housing?

I mean every part that is connected between the motor output shaft and the pad, whether that be rod, cam, lever, gears etc. It may simply need some penetrating oil followed by cleaning to get things moving again which will cost nothing. It's worth trying before spending on new parts.

4 hours ago, Marcin Z said:

When you say brake linkage do you mean the mechanical parts inside the motor housing?

Hi it could well be a seized piston that side, take the motor off and put it in lining change mode if the motor works its the calliper thats seized, all the water in the fluid collects in the piston chamber and rots the pistons.

Steve.

Thank you for your replies and suggestions. I took the motor housing off the caliper. The caliper/piston works fine and nothing is seized in that part of the system. I then plugged the motor to 12v output and it spins. So the mystery deepens. I will try to connect the motor to the plug and see if it activated when I press the parking brake button, but this will have to wait as I have run out of time now. How loud should the electric motor be? When I connected it to 12v it was spinning (both ways), but sounding quite loud. Not overly loud, maybe like a drill on a very low speed. Difficult to explain in words I guess. 

5 hours ago, Marcin Z said:

Thank you for your replies and suggestions. I took the motor housing off the caliper. The caliper/piston works fine and nothing is seized in that part of the system. I then plugged the motor to 12v output and it spins. So the mystery deepens. I will try to connect the motor to the plug and see if it activated when I press the parking brake button, but this will have to wait as I have run out of time now. How loud should the electric motor be? When I connected it to 12v it was spinning (both ways), but sounding quite loud. Not overly loud, maybe like a drill on a very low speed. Difficult to explain in words I guess. 

Hi since you have established that the motor works and the piston moves the next port of call would be the rear calliper slide pins as they seize along with the pad slider surface, you can buy aftermarket repair kits for the slide pins for about £20 could well be a build up of old rubber on the pins which means the rubbers are probably shot. And yes the operation of the motor is fairly loud like a clockwork toy.

Steve.

Thanks for the suggestion Steve, but I've checked the pins and the movement and all is as it should be. However, I have also plugged the motor back in, but without attaching it to the caliper and got another person to activate the handbrake while I was under the car. The motor did not activate. The one on the other side did. I then attached a voltage meter to the plug and again had another person activate the handbrake. The meter shown no voltage coming through. I assume in that one or so second when the handbrake is being activated there should be 12 volts coming through the plug. Similarly, no current was registered when the parking brake was being deactivated. So I am inclined to think the problem is with the wiring. The wire from the motor goes up somewhere, but I'm not sure what it connects to further up. Any suggestions would be helpful. Also, is there by any chance a separate fuse for the left and for the right parking brake?

35 minutes ago, Marcin Z said:

Thanks for the suggestion Steve, but I've checked the pins and the movement and all is as it should be. However, I have also plugged the motor back in, but without attaching it to the caliper and got another person to activate the handbrake while I was under the car. The motor did not activate. The one on the other side did. I then attached a voltage meter to the plug and again had another person activate the handbrake. The meter shown no voltage coming through. I assume in that one or so second when the handbrake is being activated there should be 12 volts coming through the plug. Similarly, no current was registered when the parking brake was being deactivated. So I am inclined to think the problem is with the wiring. The wire from the motor goes up somewhere, but I'm not sure what it connects to further up. Any suggestions would be helpful. Also, is there by any chance a separate fuse for the left and for the right parking brake?

Its highly probable there is a fuse for both L/R as if you think about it the way they do it could cause safety issues if they both worked from the same fuses try that before attacking the wiring as the way its routed it goes places you wont want to.

Steve.

Checked the fuses. They are ok. I suppose it could be a relay, but I've done some reading that seems to suggest a corrosion in the parking brake harness is not uncommon. Though the only way to check would be to cut the harness open. I think you can buy a replacement plug (the end that connects to the motor housing) with 30cm of wire or so attached to it and then do some surgery on the harness. Maybe that is the answer. In the meantime there is the red flashing parking brake warning on the dash at all times. Foot brake operates as normal (and works on the affected wheel too; I've checked with the wheel in the air). I left the left parking brake disconnected. The one on the right still works fine. 

I've accessed the wiring harness in the boot area. I've stripped a very short section of the two wires that supply power to the parking brake motor. My car is an SE model and there are only four wires in that part of the harness (two for parking brake and two for abs sensor I guess? not sure if the esp and abs is the same sensor?). I have bypassed the harness from that point and used a length of spare wire to connect the parking brake motor through an open boot lid. The parking brake engaged and disengaged as it should. I am assuming that the harness is faulty somewhere between the point where it enters the boot and where it connects to the electric motor. I was going to fashion a more permanent bypass, but found a cheap replacement harness (not OEM) and am tempted to get it and replace the whole thing. It does not look too difficult and I already have access to it from the inside, so just need to remove the wheel arch i think and then it should be fairly simple. 

One thing I will add is that even with the bypass and parking brake working, the fault on the dashboard remained. I don't know if you need to delete the fault code or should it disappear automatically once everything is working correctly? I don't have a code reader so will need to ask the garage.

4 hours ago, Marcin Z said:

I've accessed the wiring harness in the boot area. I've stripped a very short section of the two wires that supply power to the parking brake motor. My car is an SE model and there are only four wires in that part of the harness (two for parking brake and two for abs sensor I guess? not sure if the esp and abs is the same sensor?). I have bypassed the harness from that point and used a length of spare wire to connect the parking brake motor through an open boot lid. The parking brake engaged and disengaged as it should. I am assuming that the harness is faulty somewhere between the point where it enters the boot and where it connects to the electric motor. I was going to fashion a more permanent bypass, but found a cheap replacement harness (not OEM) and am tempted to get it and replace the whole thing. It does not look too difficult and I already have access to it from the inside, so just need to remove the wheel arch i think and then it should be fairly simple. 

One thing I will add is that even with the bypass and parking brake working, the fault on the dashboard remained. I don't know if you need to delete the fault code or should it disappear automatically once everything is working correctly? I don't have a code reader so will need to ask the garage.

Hi the fault will have to be deleted.