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nigel

Brake Problems

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Hi all,

 

What a great site, wish my very first post wasnt to ask about a problem.

 

My 2004 Corolla which I have never had a problem with, now has a problem with the brakes. The brakes initially work fine and bring the car to a halt no problems. But as your waiting at the lights or stop sign, the pedal slowley but surely travels all the way to the floor. The brakes will still hold the car stationary and work fine on the next application,then slowley work its way to the floor again.

 

I have checked the reservoir and the fluid level was correct. Checked around the master cylinder, slave cylinders and fittings and can't find any external leakes. If it was externally leaking I would notice a drop in fluid reservoir level and have to keep topping it up.

 

I think there may be an internal leak within the Master cylinder. Possibly past one of the cup seals. Would like to know what other mechanically minded members think. If I can be sure its the master cylinder, I can refit a complete unit or kit as I have done this kind of work before on my old Honda Civic.

 

Cheers guys, any advice much appreciatted.

 

Merry Christmas to you all.

 

Nigel

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i have the exact same problem in my ke70 but never bothered to ask about it.

so what parts do i need to get to fix this?

 

1st Dismantle the master cylinder,

 

2nd hone and inspect barrel if there are no scratches order a seal kit and reseal,

 

3rd If the cylinder is scored and wont hone out the cylinder will need to be re sleeved or a new cylinder fitted.

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Sure you have no air in your brake lines? What colour is the brake fluid? Majority of brake fluid is Blue, there is some clear kind of fluid as well. Brake fluid is hygroscopic which means it absorbs moisture. More moisture it absorbs, the shitter the brakes feel.

 

 

Change your brake fluid and bleed all brake calipers. Starting at L/H/R then to R/H/R then L/H/F to R/H/F if your master cylinder is on the drivers side.

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Turned out to be one of the cup seals on the master cylinder piston. The seal had a slight crease in it and was letting fluid fast under pressure. Also as the seal was allowing the piston to touch the master cylinder wall, there was some obvious scratching to the side of the piston where it has contacted the cylinder wall. No obvious damage to the cylinder itself, so we took a gamble and just did the kit (pistons spring, cup seals and O rings) as the kit is $180 while the complete master cylinder is $580.

 

Quick easy job to overhaul the Master cylinder. Put it all back in and bled the brakes and clutch as the clutch shares the same reservoir and you can't help but let air into the clutch feed hose when removing the reservoir.

 

The brakes now work fine. Will post picks of the damaged cup seal and piston when I get the chance. Seems strange that this component should fail on any 4 year old car let alone a toyota. Maybe write a letter to Toyota Australia if I can be bothered.

Edited by nigel

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the wrong brake fluid apparently eats things in master cylinders, toyotas seem to run a dot 3, NOT a dot 3&4 compatible fluid.

 

seems pedantic, but we have been using either toyota genuine (dear as sin, as are all toyota bits) or valvoline dot3 (blue) fluid. We had a grj120r prado with the same problem, couldn't get an aftermarket master cylinder or rebuild kit, and genuine one was poisonous, around $780 i think, if i remember right.

 

Robert.

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