Hitchcocks Forum

Hi having problems bleeding enfield disc brake changed brake hose for braided one have put app half litre through system still cant get air out of system or lever to go hard Got me stumped no leaks on hose conections, even pulled caliper off fork leg so bleed nipple was on top.
Have bleed brakes on other bike ok so I know the procedure no leaks at caliper end. Bike has only 50klm since kit was fitted couple of years ago and was ok til we changed hoses anyone can help.

Missing copper washers on the banjo bolts?

Make sure you have the master cylinder completely released as if the is any compression on the piston it will block it off. There needs to be actual flap in the lever in my experience. Then bleed from the caliper/s up by putting a reservoir as high as you can (well above the master reservoir) with a long hose connected to the bleed nipple/s. Set it up so you don't have to hold it as it can be quite slow.

Try draining down and refill from the calliper end, blows the air upwards into the reservoir.

I use a horse syringe obtained from the local vet, refit bleed with a turn or two of PTFE just to seal the thread whilst pressurising

Think i once used the clear vent tubing from the battery to connect syringe to bleed nipple..

Try tying the brake lever back against the handlebar as far as it will go and leave it overnight. Normally a thick elastic band doubled or trebled will be sufficient
On a lot of bikes this will allow the air to find its way back through the master cylinder

Thanks all we pulled the master cyl apart appears to have a gritty substance in cyl and one piston stuck in caliper looks like they used grease on the pistons usual lack of q/c, glad this was found now rather on the road where you need the disc, now just need to source parts and give houseings a good wash in meth. Who would have thought this with a new item. Thanks again.

Clear tube and jam jar to provide non-return 'bubbler' for air - have the clear tube loop up so you can see air bubbles coming out, and not going back in.

They can be a Bugger!


Use a small syringe to inject brake fluid into the master cylinder. Clearing that initial air lock in the mater cylinder can be a test of ones patience
b
Other-wise, pump the fluid up from the bottom via the bleed nipple fitting. Either way it is good to have a thrid arm/hand.

Valsp has the solution. Tiny air bubbles will, for reasons known only to people from another galaxy, sometimes form in the brake fluid. By increasing the pressure applied to the fluid there will be a significant increase in the pressure in the air bubbles and this causes them to gather together and thus form bigger bubbles which will rise through the fluid and break surface in the reservoir. Why the bubbles elect to co-join under increased pressure is known only to people of a different galaxy from the one mentioned above. I apply a pressure equivalent to that which you would use when the red and yellow striped van in the layby ahead comes into sight and secure the lever with a sturdy cable tie. Works every time. Adam

A small addendum. The bubbles will, of course, settle against the master cylinder piston overnight and break surface in the reservoir when the lever is released.