4 replies to this topic

[Monkeh]

Hi, i have a slight problem and i have no idea whats causing it.

i recently blew a piston seal and it leaked fluid, so i changed the seals for new genuine ones and it still dripped slowly from the piston seal.

I thought that i must not have cleaned the groves inside out properly so i changed the seals again only giving the groves a good scrape to clean it out. I then proceded to give the seals and piston a good soiling in brake fluid to lub it and fitted it as the instructions state.

i put the caliper back on the car and bled it, put my foot on the brake and it still leaks lol. I can just feel the brake pedal creeping down when i apply firm pressure. i cant understand why its still leaking, deffinetly from the piston.

could it just be fluid residue from where i lubricated it?

Thanks.

[Big_Adam]

Well if the seal is still leaking then there may be a defect in the wall of the piston or the caliper wall meaning you won't get a seal.

You'll need to pull it off and check the surfaces.

[mini_kel]

Take the caliper off leave hose on,and clean with brake cleaner,Then with some help apply brakes but make sure u have something in between pads to stop them popping out!! then look to see where fluid is coming from,

I would say the piston bore is scored!

[dklawson]

Minor pitting of the seal glands in the caliper is permissible, but you have to look carefully to make sure you've removed all loose material and in particular, anything that sticks "up" from the surface. The pistons on the the other hand need to be pristine. No pitting would be permissible there. You may find it necessary to remove the caliper from the car, flush out all the fluid and carefully clean the seal glands again. Though I don't recommend this for most people, I have a micro sand blaster and I have used that to clean the seal glands on calipers. Obviously the calipers have to be 100% flushed out and squeaky clean after this!

You say you can FEEL the pedal move downward when you hold the brakes on. That would be more than a small leak. Consider how much fluid comes out each time you pump the pedal during brake bleeding. A pedal that creeps down can be symptomatic of a failing master cylinder. I know you've got enough to worry about... just file that away for once you get the seal leak sorted.

[Monkeh]

thanks ill just have to take it apart again and check it. i can only feel the pedal move downward a very tiny amount, so small that i might even be mistaken.