2010 Avensis loosing Brake Fluid

[toolapcblack]

Hi all about a month ago my Avensis needed a top up of brake fluid after the dash light came on, i put this down to pad wear but on further examination of pads they aren't worn that much, less than 50%,  as i had wheels off i thoroughly examined the calipers and brake lines under the arches and could find no sign of leaking.

Yesterday the light came on again and it took over 100ml to fill it back again so i checked underneath again this checking all visible brake lines and found nothing ( i assume the straight lines under the covers would be one piece and as the the entrance and exit points were all in good condition therefore i didnt remove the covers). At no point did the brake pedal become anything but rock solid so i am now thinking this may be cylinder related as if there was a leak in the main system surely any expelled fluid it would draw air back in? leading to spongy brakes. There is also no visible leaking around the Master cylinder, or where all the pipes gather over the opposite side in a block, therefore could it  be leaking out the back into the booster unit?

Any ideas?

Thanks

[toolapcblack]

i just tried holding the pedal down with the engine off, there was no movement i must of held it for 20-30secs

[Stivino]

Double check the whole system for a leak and if you can't find one, keep an eye on the level. 

[toolapcblack]

further developments have found a leak in the rear drivers side caliper fluid is seeping out the back end where the handbrake pulls on the caliper not the pads side, are these hard to change? 

[avetoy]

If you mean the whole caliper, answer is no. It is quite easy to replace.

But fixing "back side" leak... I don´t know.

[jimtaxi]

Just replace the caliper they are relatively inexpensive, replacing the seal that's gone involves stripping the whole caliper, not worth it. Buy from a known source UK rebuilt, some cheap new items from the internet play havoc with the EPB if you have one.