04-12-17
Brake Fluid Fail
Working with the brakes has been the most time consuming aspect of this build so far. Shimano documentation leaves out many steps in the bleed process and the practicalities of this particular application required a bit of creativity.
The bike went up in the stand sans wheels. Brake pads were removed and yellow bleed blocks put in their place. The fluid port at the top of the brake levers needs to be the highest point and so the bike was rotated in the stand with the bars up. This nose-up orientation required securing the bars with string so that they wouldn't flop over. In retrospect I probably should have loosened the face plate on the stem and just rotated the bars but that would have been way too easy and wouldn't have looked nearly as rediculous. I clearly wasn't at my best mentally.
Nevertheless, the fluid port on the brake lever was opened with care taken to ensure that the o-ring isn't lost. The funnel from the Shimano
TL-BT03 bleed kit was screwed into the fluid port's threaded opening. Down at the caliper, the rubber dust cover was removed from the bleed port, a 7 mm box wrench was placed over the port and the hose from the syringe was placed over the nipple. The hose is secured on the nipple by way of a black plastic tool which gets jammed against the nipple. Unsure of how much fluid the system would take, I filled the syringe all the way.
Fluid was pushed up through the system until the funnel filled. The syringe was then replaced with a different hose connected to a plastic bag and the fluid allowed to drain back down through the system into the bag as per Shimano documentation. Several iterations of opening and closing the bleed port while depressing and releasing the lever followed, also as per Shimano documentation. No bubbles were seen in the fluid either up top at the funnel or down below at the caliper and so the fluid port at the lever was sealed, bleed nipple at the caliper closed, oil cleaned up and pads/spring reinstalled along with the orange Shimano brake block.
The brakes felt horrible with the levers going almost all the way to the bar. I repeated the entire process to be sure that there wasn't still air in the system but results were the same. The classic definition of insanity prompted an evening of rereading documentation, watching videos and looking at message boards in an effort to determine what I missed or did incorrectly. Bleeding brakes isn't theoretical astrophysics and something is clearly missing from the process I am using.
One thing my reading revealed is the presence of a free stroke adjustment on the brake lever. Apparently this is set to the minimum setting from the factory and according to the internet, has to be set to maximum for bleeding. The publicly available Shimano documentation does not make mention of the free stroke adjustment as part of the bleed process but according to some the Shimano S-Tech website available to dealers and technicians does. It's worth a try. Feel free to post your ideas.
-Tim-