Changing pads
My 2006 Prius T-spirit has covered 62,000 miles and the last MOT advised replacing the front brake pads in the near future. I would normally have no hesitation in doing this myself and have ordered a new set of Bosch pads for less than £23.
Having now read some internet stories about this task, I am hesitating as the job is not quite as straightforward as with most cars. The brake fluid is under permanent pressure, even without the engine running, and I have read that the safest way is to either disconnect the 12-volt battery or else remove two relays which will cut power to the appropriate pump. My key is not the smart type and should not need to be away from the car, so perhaps I would just need to ensure the key is not in its slot before starting work?
Would I need a special tool in order to push back the brake pistons and could I slacken the bleed nipples to allow the brake fluid to flush out while pushing back the pistons? There appears to be a risk of dash warning lights coming on following pad renewal, so would I need a special code-clearing device for this? My local Toyota dealer has quoted £95 for replacing the pads, but I hope to avoid paying this if possible and I am not sure if other garages will have the correct codeclearing device.
Alan Forshaw
As you have discovered, the brake system on the Prius is different to most vehicles in the fact that it has an electronicallyoperated hydraulic system, using direct hydraulic pressure only when the vehicle is stationary or moving below 7mph.
This system employs pressure sensors on the master cylinder and the caliper, checking for any difference in pressure through the brake lines. Another problem when working on the Prius is that, if the ignition is on, the engine may start at any time the vehicle systems determine it is needed; for this reason, the key should be away from the vehicle. Because of the regenerative braking system used on the Prius, the brake pads should last a lot longer than would be expected on a conventional vehicle, but they will eventually need replacing.
With the keyless ignition arrangement, before working on the brake system, you are advised that the ignition must have been off for at least two minutes prior to
work to allow the system to power down. Keep the remote fob away from the vehicle and do not open the doors while working on the brake system. You should also remove the two ABS relays from the fusebox under the bonnet – these relays should be blue. The rest of the pad change should be the same as any conventional vehicle.
Toyota advises gently pushing in the caliper piston only enough to fit over the new pads and shims. It is not necessary to undo the bleed nipples during this procedure and doing so could cause more problems than it solves. After fitting the pads, the brake pedal should be pumped gently to locate the pads, before replacing the ABS relays and turning on the ignition.
When first turning on the ignition, an ABS light may illuminate. Take the vehicle for a short drive and then turn off the ignition; when turning on again the ABS system should self-test and turn off the light. Toyota also says that it is possible an ABS code (C1341/2) may show up after the work has been carried out and will need to be cleared using a suitable scanner.