BKHC02 & BKHC04 Brake Bleeding Procedure

Internally we use a brake bleeding tool which is basically a vacuum pump with a line to suck the fluid through – it’s worth having one of these if you’ve got hydraulic brakes as it makes the process so simple with one person.

It can be done without the tool though, although without the tool, the job is easier with 2 people.

Open the reservoir lid on the master cylinder and top up with brake fluid. Dot 3 or 4 is fine. Close the lid.

Crack the bleed nipple on the callipers with an 8mm ring-end spanner. Open end spanners might damage the barb. Be careful with the thread as the body of the calliper is aluminium.

Pump the lever on the master cylinder by hand. If nothing comes out of the bleed nipple, unscrew it further until you can hear either air or see fluid coming out.

Once you can see or hear air/fluid coming out of the callipers, close the bleed nipple by doing it back up just enough to stop the air/fluid coming out.

Pump the lever on the master a few times and then hold pressure on it. Crack the bleed nipple on the callipers enough to let the pressurised fluid/air escape and close it off again before the lever reaches the end of it’s travel.

Repeat this step until fluid flows out of the barb without any sign of air bubbles. Don’t forget to periodically check the master reservoir and top it up – do not let it run dry! This will run out as you bleed the system as you’re pushing this fluid through and out of the end of the bleed nipple all the time during the process.

A top tip here is find a piece of vacuum hose or hose with an ID about the size of the bleed nipple barb and run it into a plastic container. Put a little brake fluid in the container – it will fill more during the process. You will be able to see if air is still coming out because the bubbles will be easily seen in the plastic container full of fluid (they will bubble to the top of the fluid). When you no longer see bubbles you’re done.