bleeding brakes

[handsomejackuk]

Hi,

I have been trying to bleed my brakes with no joy as yet. any tips ? I have completely emptied my master cylinder hose and caliper because i wanted to clean caliper and paint up my master cylinder and hose. I now have fluid up to the master cylinder i know because i have take off the hose. but i am having difficulty geting fluid to come through the hose. i may try reverse filling from the caliper end with a syringe of brake fluid to see if i casn get fluid thoruigh that way and advice ?

Alun....

[Fil]

I was just going to suggest what you have already - use a syringe and gently push fluid into the system via the caliper.

I had the same problem as you in that it's very difficult/ time consuming trying to get any kind of volume of fluid through the brake system by pumping the lever.
It was so much easier with a syringe and some silicone hose to connect it to the bleed nipple.

[handsomejackuk]

Fil,

I just phone my missus, she works in a hospital and asked her for some syringes she asked what for i said for my habit.... she gonna bring some different sizes home tonight i'll give it a go then .........


THanks Al.......

[Fil]

Nice one Al.
You just need to get some tubing that will fit on the syringe and the bleed nipple.

Good luck with it mate! Hope it works Ok.

[handsomejackuk]

Spent two hours today with syringes and pieces of plastic tubing trying to fill up hoses and caliper got most of the brake fluid over my patio and consequnetly tipped a 1/2 full carton of syntheitc fluid all over the patio real pisser of a job and its still not done... what ive noticed is that the rear brake hose goes from the master cylinder and loops arounf top mount of rear shocker which is higher than the master do you think there could be an air lock here do all bikes have the hose going aroung to top mount higher than mastr cylinder ? did paint my hose ends and bleed nipple in a nice black but now my hoses lok worse than when i strated originally may take it to a local bike shop and get them to do it as iam pisst noww....

THanks Al

[DAVID THOMPSON]

the rear unit on my rt125 was a real pain

but i noticed i could get the whole system off the bike in one piece

so did it off bike
put a wood wedge between the disc pads and hung the whole mess
from the over head then pumped new fluid in from the brake pad end
works now but still feels funny

guess i will give it a go again this winter



ar dave

[Fil]

Spent two hours today with syringes and pieces of plastic tubing trying to fill up hoses and caliper got most of the brake fluid over my patio and consequnetly tipped a 1/2 full carton of syntheitc fluid all over the patio real pisser of a job and its still not done... what ive noticed is that the rear brake hose goes from the master cylinder and loops arounf top mount of rear shocker which is higher than the master do you think there could be an air lock here do all bikes have the hose going aroung to top mount higher than mastr cylinder ?

Don't give up just yet mate!
I'm sure you're doing it right, but I'll just explain what I did with my front brake:

Take the cap off the brake master cylinder reservoir, along with the rubber diaphram.

Get your syringe and fit a suitable hose over the end.

Use the syringe to suck out as much brake fluid as you can from the reservoir without uncovering the hole(s) in the bottom of the reservoir.

Discard the fluid you sucked out, and fill the syring with clean brake fluid.

Push the syringe plunger down until the hose on the end is also full of fluid.

Stick the open end of the hose onto the bleed nipple on the caliper and make sure it's a good tight fit - try using a zip tie if needed.

Open the bleed nipple and gently but steadily push the fluid in through the bleed nipple until it comes out into the master cylinder reservoir.

Keep going until the reservoir is as full as you can get it without it overflowing - keep a close eye on it as brake fluid will strip paint.

You also need to keep an eye out for any bubbles. You will hopefully see bubbles to start with in the reservoir, and then they should stop once you've pushed enough new fluid through.

Before you stop pushing on the syringe plunger or run out of fluid, nip up the bleed nipple.

If you were still getting bubbles, you will need to repeat the process. Just remember that because you are reverse bleeding, each time you stop and remove the syringe/hosepipe, you will probably get a little bit of air in the system when you re-connect the hose, so it pays to have a decent sized syringe, and if you can, get another syringe and a helper to remove fluid from the reservoir if it gets close to overfilling. That way you should be able to keep going until the job's done without having to stop and reconnect the hose/syringe.

Apologies if I'm teaching Grandmother to suck eggs, but I hope it's of some help

Regarding the rear brake line - yes it's a heck of a long line! I guess that was the only way they could keep it far enough from the exhaust to prevent the fluid being heated up...
If you reverse bleed the rear too, you shouldn't have to worry about airlocks in the loop over the shock. I also found it easier to unbolt the rear fluid reservoir so that I could try and keep it level and to get better access for removing fluid/refilling.

[jimc]

Couple of things that might help:
Is the lever return travel restricted? if the master cylinder piston seal doesn't clear the reservoir port, it will never work. At rest, fluid should slowly drain thru the master and out the hose
Try pumping fluid thru the hose disconnected from the caliper. Hold the lever down while reconnecting to the caliper. to prevent draining.
When bleeding, return the lever slowly.
Synthetic (silicone based) brake fluids are more difficult to bleed than conventional DOT3 or 4 fluids. Even after bleeding, these fluids are more compressible . I can see the need if you have really high brake temperatures or expect to ride in the Arctic. Silicone is also good for show cars or garage queens.
You might try positive pressure bleed - cob up a flat plate ( or butcher a spare cover) to cover the reservoir with a tube fitting & rubber gasket - fill the reservoir, add less than 7 psi air, and bleed. Do not pump. Do not let reservoir run out.
The syringe setup is also useful as a vacuum bleeder - crack it and pull fluid out - no pumping.
Maybe you have some bad seals?
Good luck.

[handsomejackuk]

THanks for info on this topic guys,, Think i will try fils idea 1st to see how i ge ton. One question should my pistons be fully out i.e. pads almost touching disk, or pushed back ? at the moment they are fully back i.e. pads loose.

I did try vacuum pulling fluid through and this seemed to work but I was in such a mess i gave up and went for a spin on my other bike.

Fil, when reverse bleeding where should the brake pedal be on or off ?

thanks Al..........

[Fil]

I've only tried this on the front brake, but it should be the same - the brake should be in the 'off' position.

jimc's idea with positive bleeding from the level end would also be a good solution if you can make up a suitable plate and seal it properly (for the front brake). You could try doing the same with the back, but you'd need another resrvoir cap to modify. Also, when I tried this on my car, it didn't seal properly and I ended up spraying the engine bay with brake fluid

You'll get there in the end...

I forgot to say - the pistons will be out - ie pads against the disc when you've finished, because when you pump the pedal to check for spongyness/ feel the pistons will push outwards until they push the pads to the disc.

[handsomejackuk]

Hi,

Seem to have solved my brake problem. Reverse filling the hose seemed to work I pushed the pistons completely out against the pads using a cycle track pump connected to the inlet to caliper with nipple closed. then filled the caliper with fluid from the nipple side then proceeded to fill the hose from brake nipple side. I then made sure I had fluid up to the master cylinder outlet, put my finger over the outlet of the master cylinder to keep fluid there, then connected the hose. Filled the master cylinder with fresh fluid and bled the system. took a while to get all the air out but think I am there now. Only problem seems to be my pads are not very good. I did clean them up but think I need some new Pads...


Thanks Fil and others for advice....seems to work M.O.T. today then Tax beginning of August...


Regards Alun

[Fil]

Cool, glad you got there in the end mate.

Hope she passed the MOT today!

[handsomejackuk]

yeah flew the m.o.t. no probs taxed him for a year god i'm treating myself....

went for a spin to the Brecon Beacons yesterday met up with a guy with a KTM 640 and went for a spin with him his bike sounded great with akraprovic can on cant wait to get my vampire sent and put on .........

Thanks for now guys...

Alun....