pinched hose somewhere? meaning fluid can get pushed towards the caliper but isn't moving back out from it quickly?
Another thought on this , I've seen the seals on the master cylinder replaced the wrong way round . That definitely keeps the brake on .
I’m my case, I have a brand new rear caliper. Same thing happened again. I had a thought, does air expand more than brake fluid when heated? If so, if there’s air in the pipe near the back of the engine it will expand, pushing the pads into the discs, generating more heat, etc etc. ?
worth having a peruse through this lot, it's an age-old topic, if you lived nearer then would be happy to pop round. :- https://www.ducatiforum.co.uk/search/273266640/?page=9&q=rear+brake&o=relevance&c[node]=91+115
The problem with air or any gas is that it compresses so instead of the pressure pushing the piston it squeezes the air. If expansion was an issue the fluid would expand more than air.
If you are brave (and it fits) you can try swapping around. try the rear caliper on the front master and vice versa. Could prove which part of the system is the issue.
Well thanks guys but just to clarify a few useless reply's ! (joke appreciate the input) No kinked hoses Seals correct way in master -wouldn't get pressure if not Air is easier to compress than oil, hence taking up the expansion when over heating not allowing brake to drag. The cap isn't blocked design is that expansion is held in the system, grooves in cap and taken up by rubber bellows. I'm not riding the brake with my foot !! I tried forcing fluid back in to reservoir by pushing pistons, i couldn't, no blockage as it bleeds perfectly, no non return valve so odd.(maybe amount of fluid in system ?) I replaced pads with genuine Brembo, bled on top of disc, reduced fluid to just over minimum and left about 10mm of free play in pedal. Been out for 20 miles and so far so good. Thanks all
@P1mao is everything still good, two months later? I haven’t dealt with mine yet, been running in my new bike, but I have a trackday soon so need to sort it out.
That's the root of your problem ..... right there . It is not normal for hydraulic systems ..... when you find the reason you'll fix the problem
"The cap isn't blocked design is that expansion is held in the system, grooves in cap and taken up by rubber bellows." not sure what this bit means.
We had this with my lads MX125 rear caliper no amount of reverse or conventional bleeding worked. Ended up purchasing a cheap £15 vacuum bleed set from the the bay of E, worked a treat. The master cylinder on the Aprilia is on the opposite side of the frame to caliper and has a very convoluted route it has to follow so unfortunately the raising the caliper trick was not possible.
The grooves on the cap allow the bellows to retreat if the fluid is at the correct level, the system is sealed by the bellows and expansion and contraction acts in a sealed system, fluid wouldn't last 5 mins if air was allowed to come in contact as its hydroscopic.
This is an old thread now, been working fine stripped cleaned and all ports clear, new seals in all, lots of free play and genuine Brembo pads.
Still confused and wasn't sure if it was linked to something I posted earlier on the thread, but as long as the collapsible rubber void bellows and cap within the reservoir (0000.61078) are all in good working condition then you can cross this off the list. As said, if not working correctly e.g. positive air pressure rather than neutral air pressure above the collapsible bellows, then symptoms can be as described with brake locking on. I can add "ask me how I know this" at this point. The occurrence is highly unlikely, but can't be ruled out, just depends how thorough you want to be.
Had a similar issue this past Sunday that left me and my 998 stranded. At first I thought the engine had seized up but turns out the rear brake seized up without it even being used. Rotor glowing red and bleed nipple cap burst off with the pressure. For safety I had the bike towed. Working on the rear calipers now to try and diagnose the issue.
