I changed brakepads on my Felicia today, and while pushing back the pistons the calipers started leaking brake fluid.

I have previously performed this operation without problems, but this time both calipers started leaking.

I do it like this: I place one of the old brake pads on the piston, and then use a clamp to push it back. It is not a U-clamp, though.

Can anyone give me a suggestion as to what happens.

Is it because the push is not 100% straight? Is it because the seals may be old and more sensitive? Or could it be that there is something else wrong more upstream in the hydraulic system?

Please help. I have no idea what went wrong.

Regards

Stefan

If it leaks, there's a problem with the seals - the pistons are machined to a close enough tolerance that they won't really get skewed, unless they're nearly popped out. Using a G-clamp would be a better idea, though, I'm sure.

I've never made any leak, and I've done a LOT of brakes. Usually the only problem is where people have filled up with brake fluid in between and then the master cylinder overflows...

I used this method with a G clamp with no problems on my old Favorit. However, I have just read in the Haynes brakes techbook that the correct method is to clamp the hose, undo the bleed nipple half a turn (with tube into glass jar), and then do the clamping, then close the bleed nipple. I'd be worried doing this would leave air in the system, although it does seem to make sense not to force fluid back up through the system and abs pump etc when it may have little bits and contamination etc.

Thanks for the replies.

I have taken out the calipers now, removed the pistons and inspected the seals. Everything looks brand new. There is no corrosion on neither cylinder or piston and the seals have no scratches or dis-figurements (correct word in english?).

I am wondering whether it is possible that the seals will be alright if I assemble everything again, and that the leaking fluid was caused simply by pushing the piston back at an angle but without really damaging anything. What do you think?

By the way, I havent been able to see in my Haynes how much braking fluid is required if you let everything drain out. Do you know?

There's no capacity given, IIRC.

Can't see that the Haynes method would lead air to get into the system if you did it properly (i.e. with a tube attached to the nipple), although if you're going to do that you may as well flush the system with new fluid (all the way down to the nipple, as you see the clear fluid come out) and then change the pads - there will only be clean fluid moving about then, and you'll be more likely to have removed any crap from the system in the process.

Amount actually needed is probably small, 1.5 litres or less, I tend to over-do it though to make 100% sure it's flushed through and there's no crap left in, hence I buy the 5 litre bottles of brake fluid from Halfords.

^^ haha yeah i always 'forget' how little fluid there actually is in the system, i always buy the 5 litre bottles then only use like half a litre then end up throwing the rest away

same thing with the power steering fluid too, it takes less than 1 litre to fill the entire system from dry

Yeah, I think it was under a litre to do the brakes from dry on the car, in fact.