Rav4 Brake Master Cylinder

[jedmonds]

Hi,

Problems seem to be coming thick and fast for me at the moment.

I think the master cylinder has failed on my RAV4. I've just changed the front pads, all very easy, and took her for a test drive to bed them in a bit. Brake pedal very spongy. Noticed that I could push all the way to the floor if I kept the pressure on the pedal. Brakes work fine intially but with sustained breaking once pedal reaches the floor the brakes don't stop the car any more. Have bled the system 3 times in case some air got into the system somehow, but symptoms persit.... No leaks anywhere... Pumping the pedal brings back resistance and brakes recover.

Could it be anthing other than master cylinder?

Can anyone recommend where to buy one?

Is it easy to fit? Looks accessible...

Many thanks...

[Mach 1]

Hi,

Problems seem to be coming thick and fast for me at the moment.

I think the master cylinder has failed on my RAV4. I've just changed the front pads, all very easy, and took her for a test drive to bed them in a bit. Brake pedal very spongy. Noticed that I could push all the way to the floor if I kept the pressure on the pedal. Brakes work fine intially but with sustained breaking once pedal reaches the floor the brakes don't stop the car any more. Have bled the system 3 times in case some air got into the system somehow, but symptoms persit.... No leaks anywhere... Pumping the pedal brings back resistance and brakes recover.

Could it be anthing other than master cylinder?

Can anyone recommend where to buy one?

Is it easy to fit? Looks accessible...

Many thanks...

Don't be too hasty Jedmonds, I get this problem loads of times. Basically the old discs have a lip on the that stops the pads contacting the whole disc surface squarely and the pads tend to move too far to compensate. Give the car a couple of days driving and braking and the pads should bed in to where they were before. You could change the discs aswell, that will help, but try running it around first.

[jedmonds]

Hi,

Problems seem to be coming thick and fast for me at the moment.

I think the master cylinder has failed on my RAV4. I've just changed the front pads, all very easy, and took her for a test drive to bed them in a bit. Brake pedal very spongy. Noticed that I could push all the way to the floor if I kept the pressure on the pedal. Brakes work fine intially but with sustained breaking once pedal reaches the floor the brakes don't stop the car any more. Have bled the system 3 times in case some air got into the system somehow, but symptoms persit.... No leaks anywhere... Pumping the pedal brings back resistance and brakes recover.

Could it be anthing other than master cylinder?

Can anyone recommend where to buy one?

Is it easy to fit? Looks accessible...

Many thanks...

Don't be too hasty Jedmonds, I get this problem loads of times. Basically the old discs have a lip on the that stops the pads contacting the whole disc surface squarely and the pads tend to move too far to compensate. Give the car a couple of days driving and braking and the pads should bed in to where they were before. You could change the discs aswell, that will help, but try running it around first.

Ok, you may be right, I've driven it about a bit today and it seems to stop alright most of the time. I'll do as you say and give it a little more time.

[anchorman]

What do you mean the brakes don't stop the car any more? Do you do this test moving along or are you assuming they don't work because the pedal goes to the floor. Turn the engine off and pump the pedal until it goes hard. Leave it a few seconds and press it again it should still be hard. Now if you start the engine the pedal will go to the floor. It does on mine and it is normal.

[bothwell_buyer]

What do you mean the brakes don't stop the car any more? Do you do this test moving along or are you assuming they don't work because the pedal goes to the floor. Turn the engine off and pump the pedal until it goes hard. Leave it a few seconds and press it again it should still be hard. Now if you start the engine the pedal will go to the floor. It does on mine and it is normal.

haha - is that why you changed cars? Rear ended a train? :lol:

I'd a Volvo and a Jaguar that did that too!

Got the opposite problem now.... hit the brakes on number 1 and the passenger with seat flies through the windscreen!

[saffron]

What do you mean the brakes don't stop the car any more? Do you do this test moving along or are you assuming they don't work because the pedal goes to the floor. Turn the engine off and pump the pedal until it goes hard. Leave it a few seconds and press it again it should still be hard. Now if you start the engine the pedal will go to the floor. It does on mine and it is normal.

Hi Anchorman,

Have just done a brake fluid change on my Rav and noticed the same effect. Brakes work fine and the pedal is hard when engine is off but gradually goes to the floor when continually pressed with the engine running. Can't be sure but don't think it did so before I changed the fluid. I was going to take it to the dealer to have it checked out but if, as you say, it is normal I won't. Someone mentioned that this effect is due to the "compensator"?? whatever that is?

[Mach 1]

What do you mean the brakes don't stop the car any more? Do you do this test moving along or are you assuming they don't work because the pedal goes to the floor. Turn the engine off and pump the pedal until it goes hard. Leave it a few seconds and press it again it should still be hard. Now if you start the engine the pedal will go to the floor. It does on mine and it is normal.

I agree with what you are saying Anchorman, the only way to test brakes is to road test them, standing still and pushing down as hard as you can on the brake pedal proves nothing . A lot of cars i have worked on can have a little bit of creepage on the brake pedal yet the brakes are fine when braking at any speed. you could argue that the only thing that could cause the pedal to creep down (if there is no air in the system) would be the master cylinder allowing fluid back to the reservoir but I've changed master cylinders before and still ended up with the same problem.

I still say Jedmonds problem is down to the pads not bedded in properly yet

[anchorman]

What do you mean the brakes don't stop the car any more? Do you do this test moving along or are you assuming they don't work because the pedal goes to the floor. Turn the engine off and pump the pedal until it goes hard. Leave it a few seconds and press it again it should still be hard. Now if you start the engine the pedal will go to the floor. It does on mine and it is normal.

Hi Anchorman,

Have just done a brake fluid change on my Rav and noticed the same effect. Brakes work fine and the pedal is hard when engine is off but gradually goes to the floor when continually pressed with the engine running. Can't be sure but don't think it did so before I changed the fluid. I was going to take it to the dealer to have it checked out but if, as you say, it is normal I won't. Someone mentioned that this effect is due to the "compensator"?? whatever that is?

Yeh its OK. Nobody notices before they work on them but just tend to look afterwards. I can assure you mine does it and so did the red one. As Mach 1 says it might improve a tad with bedding but I can assure you it will always do it to some extent. Its a measure of how how powerful the servo is and the ABS unit reacting to what you are asking - more pressure!