D4-d 2.0 T3-x Hatch - Soft Brake Pedal With Engine On

[razvan]

Hi! I've recently bought a Toyota Avensis D4-D 2.0 T3-X Hatchback (Oct 2003), it had 62000 miles, now is 65000 m.

Whilist I've returned from a 250 miles trip, just near home I've pressed the brake pedal at a traffic lights and I've noticed that the pedal was softer than usual, it was a 2 times longer press than usual (almost to the floor) to stop the car and it wasn't more than 40 m/hr. Released an pressed back again was more firm. I've seen the handbrake light flashing once during the trip (first time since I have the car).

I've recently change the front discs and pads, after this operation the brakes were very noisy, took it back to clean the dust, now is fine, but for three weeks probably I've used breaks more than normal because of this, first press soft to eliminate the sound and than harder to stop the car.

Anyway, second day after the trip I've started the engine and pressed the brake with car stopped and the pedal was hard till halfway an then keeping pressure on it it was slowly moving to the floor and I heard the sound of air released inside under the dash (first time I noticed that). If pressed 2-3 times the pedal gets very firm but even so, if you keep it pressed a few more seconds it starts to move slowly to the floor and you can hear the sound of air released. When engine is off the pedal is firm and remains like that.

I've took the car to the garage, tested for one day, nothing wrong in the breaking system but the advise was that the ABS unit is playing around and needs to be changed (the price is quite high even for a second hand ~ 700 £ including fitting) because it will get worse in time and it can become unpredictable.

I've took the car also to Toyota dealer and after a test drive, one of their mechanics assured me that it is normal for pedal to easily go to the floor and air sound to be heard when engine on and is nothing to worry about, in fact he says I should be worry if I will not have it. Since I don't remember how it was before the trip I can't say he is right or not.

I've done some breaking test drive on my own and ABS is working, pedal is usually firm but it happened a couple of times to be softer and it happened when I didn't expect, like first press was firm, car almost stopped then moving slowly the car (parking) and pressed again pedal was 3 times softer and I've pressed it almost to the floor.

Have anyone experienced this, is it normal to hear the sound of air released under the dash when you keep pressing the pedal with engine on and pedal to almost touch the floor? Can ABS unit be blamed for this kind of behaviour or is something else?

[Penfold]

Hi, STOP driving the car immediately. It IS unsafe. Get it to a repair shop.

What you describe is a "spongy pedal". It is a sign of air or moisture in the braking circuit. When you press the pedal the first time you are compressing the air bubbles, when you press it the second time you are compressing the air and fluid hence the brakes work more effectively.

You need to have the brakes bled and ideally new fluid throughout. MrT do it as part of the major service routine but you can also take it to Thickfit as an interim rather than travel to a main dealer.

However - it sounds like you also have a problem with the brake servo. This unit used the vacuum of the intake manifold to reduce the human effort required on the brake pedal. Generally speaking there is enough of a vacuum left in the system for a single brake application with the engine turned off. With the engine on it is unlimited. The higher the engine revs the more vacuum = more power to the servo. You should not be able to hear this servo hissing if it is in good condition.

Get an independant machanic to check the brake over thoroughly, perform a fluid replacement and a vacuum test on the servo to see if it has a split diaphragm.

The cost of this will be less than the excess on your insurance when you don't have time to hit the brake pedal twice......

[razvan]

Hi, STOP driving the car immediately. It IS unsafe. Get it to a repair shop.

What you describe is a "spongy pedal". It is a sign of air or moisture in the braking circuit. When you press the pedal the first time you are compressing the air bubbles, when you press it the second time you are compressing the air and fluid hence the brakes work more effectively.

You need to have the brakes bled and ideally new fluid throughout. MrT do it as part of the major service routine but you can also take it to Thickfit as an interim rather than travel to a main dealer.

However - it sounds like you also have a problem with the brake servo. This unit used the vacuum of the intake manifold to reduce the human effort required on the brake pedal. Generally speaking there is enough of a vacuum left in the system for a single brake application with the engine turned off. With the engine on it is unlimited. The higher the engine revs the more vacuum = more power to the servo. You should not be able to hear this servo hissing if it is in good condition.

Get an independant machanic to check the brake over thoroughly, perform a fluid replacement and a vacuum test on the servo to see if it has a split diaphragm.

The cost of this will be less than the excess on your insurance when you don't have time to hit the brake pedal twice......

The independent mechanic said everything was checked and is fine and only ABS unit is playing around (the best guess) and need to be changed! But, I have no warning lights on dash and this intrigues me, it's not easy to spend 700 £ for just a guess!