My rear Shimano MT500 hydraulic disk brake has acting up for a while. After doing a full bleed and new set of pads it would be fine for about 2 weeks then start rapidly losing performance and screeching. I did this a couple of times to see if the problem would appear in the same way which it did, noticing oil on the pads each time.
I put a bit more time into bleeding the rear brake again - now when the brake lever is pushed fluid seeps out of the bleed port. This is happening even with the cup still on the lever and the system still open! Surely the pressure should be releasing from the top port which is open?
During the bleed I noticed when I pulled back on the bleed port syringe there as a lot of small bubbles and it felt like no air would release and the pressure would snap the syringe handle back in, though it seemed fine when pushing fluid out towards the brake lever. Could something be blocked?
I'm supposed to traveling with this bike on Saturday so I'm not sure if its worth just purchasing a new back brake now in case it's unlikely to be repaired on time? It's cheap enough to be worth it if required though I'd likely have to fit it myself in this timeframe, which I've not attempted before though does appear somewhat straightforward (though so did brake bleeding!).