bleeding brakes - problem

[Dave20046]

Hi guys having a real F around with my bike.
Stripped a caliper but it back together; went to strip the other and there wasn't enough pressure to pop out the pistons. I've bled the brakes both via the nipples and via the syringe method but there is still no resistance on the lever. Any Ideas???



(sorry if this is a repost but I need my bike for tomorrow morning and no one takes notice of posts at the **** end of old threads)

[flymo]

here's where you'll get 100 different ways to bleed brakes.

in my own experience I've found the best way to do this is with a clear plastic tube connected to the bleed nipple. Raise the tube up into the air and fasten it to something. Open the bleed nipple and leave it open. Pump your lever slowly for a few secs. If you're lucky you'll see the fluid and bubbles make their own way out into the tube. Keep the fluid topped up in the brake res.

After you can see the fluid appear from both nipples, nip them up and bleed conventionally. Tube on one nipple, spanner at the ready. Apply pressure to the lever and open the nipple, close the nipple before you release the lever pressure. Repeat until you get no further bubbles.

Swap calipers and do the same.

It may well help if the bike is on its side stand to expel any air at the master cylinder up near the bar.

[maviczap]

Maybe the seal has gone at the brake lever end. I can't for the life of me remember the technical term at the moment, but symptoms of no pressure in the system must start from here.

[Dave20046]

Cheers flymo before I attempt your way I'm actually startign to think there's a problem else where if I open the bleed nipple (no tube on it) then squeeze the lever what should happen?

At the moment the occasional jet'll spray out a few cm then nothing or it's dribble a few drops then nothing.

[Dave20046]

Originally Posted by maviczap

Maybe the seal has gone at the brake lever end. I can't for the life of me remember the technical term at the moment, but symptoms of no pressure in the system must start from here.

That's what I've been starting to think

[Dave20046]

I can't see how there can be any air in the system as I've pushed fluid up from the nipples to the reservoir.

By the sounds of it the brake system isnt fully full of fluid yet. If you have a syringe then try filling it with brake fluid, open the bleed nipple, connect on the syringe then push fluid through the system. You should see fluid with air bubbles coming into the res, eventually it should just be fluid, when this happens bleed it the conventional way.
I'm doing my brakes soon, i hope it goes well!

Damn you posted whilst i was writing, did you make sure it was just fluid coming through?

[flymo]

if the seals at the lever were ok before then no reason why they wouldnt be fine now. more than likely air in the system.

Every time I've ever had trouble bleeding brakes its always been trapped air, never a dodgy seal.

[Dave20046]

Originally Posted by SVDragRacer

By the sounds of it the brake system isnt fully full of fluid yet. If you have a syringe then try filling it with brake fluid, open the bleed nipple, connect on the syringe then push fluid through the system. You should see fluid with air bubbles coming into the res, eventually it should just be fluid, when this happens bleed it the conventional way.
I'm doing my brakes soon, i hope it goes well!

I syringed fluid up the system via each caliper (through the nipple) until I saw the reservoir level raise near to the top. At this point I assumed their couldn't be anymore air in the system as fluid had made it's way to the top of the reservoir (was I wrong??)


incidentally does it matter if I get a bit of brake fluid on the front tyre?