Help Bleeding Brakes

Steevwatson

New Member
After riding my bike which was upgraded to hydraulic brakes my girlfriend has decided she wanted to upgrade too. She loves a bargain and picked up a used set of Shimano brakes and levers from Gumtree for £20 they look like these ones on Ali express https://m.aliexpress.com/item/40003...hp5wtK1conrHvw1603886002833&browser_id=&is_c= they have the correct connector for the rad bikes too. I've installed the front brake and it works very well motor cut off etc all working. Now here's where I'm hoping you guys can help.

The rear brake came with the hose detached from the lever as the seller had tried to feed the cable through his bike frame. So I've reattached the cable using a new insert and olive. The brake is obviously full of air and very spongy to the point it doesn't fully stop the rear wheel. I've got a bleed kit and I'm trying to bleed the brakes but for some reason I can't push oil into the caliper and when I try to drain oil out no oil drains from the caliper. When I squeeze the leaver oil does flow out of the bleed nipple on the caliper but when I release the lever it is sucked back up the hose.

I've tried following the instructions in this YouTube video but I'm now stumped.
Any ideas before I just put the stock brakes back on?
 

smorgasbord

Well-Known Member
Region
USA
When I squeeze the leaver oil does flow out of the bleed nipple on the caliper but when I release the lever it is sucked back up the hose.

I've tried following the instructions in this YouTube video but I'm now stumped.
Any ideas before I just put the stock brakes back on?

Use the two-handed method, which is better anyway:
1) Open the top port, close the bottom port
2) Make sure the funnel is about half full of oil
3) Squeeze the lever
4) While holding the lever, open the bottom port by the hose to let oil/air out, then close the bottom port
5) Release the lever
6) Re-open the bottom port
7) Go to step 2 and repeat until you're satisfied that you've replaced all the oil in the system

None of these procedures are fool-proof, because bicycle hydraulic systems are so small it's easy to get little air pockets that "stick" to the sides of tubing or other areas. After you do the above, leave the top port open and literally flick the lever housing a few times to try to release those air pockets, which should float up and into the funnel. Then, close up and you be good to go.
 

theemartymac

Active Member
And make sure the bike is somewhat level with the lever well above the caliper. a lot of bike stands lean forward and the low spot in the line can be hard to purge with the gravity method.

If it doesn't improve, you could try the two syringe method, and push the fluid back and forth several times until the bubbles are out.