bleeding front brakes dilemma. PLEASE ADVISE.

[Jai466]

Hope you members can help please.

One of the pistons in my front brakes were sized and I decided to rebuild the caliper.

I brought some dot 4 brake fluid from Halfords and filled the reservoir to full, I’m using the Haynes manual and it says there that I should 1st pull the brake leaver a few times until there are no air bubbles appearing from the reservoir. The problem is that I’ve been pumping the brakes for 3 hours and the bubbles don’t stop.

I them brought a one man bleeding kit for £3.99 from Halfords and open the bleed nipple and started to bleed the brakes. There seems to be extremely small thousands of air bubbles appearing in the lube within the brake fluid, from the bleed tube. I then thought that it could be air entering from the nipple and then put some plumper tape around and retired, still same issue.

The bleeding took too long and I just decided to close the nipple and pump the brake leaver until the bubbles stop appearing.

To be honest they didn’t stop and I gave up, there still was pressure in the system as the brake would apply.

I filled the reservoir and took the bike out for a ride… hoping that the brakes would work. I was testing and trying out emergency stop and worked fine at about 35mph, fastest I could go due to road length.

How would I go about removing the air from the system as there are bubbles from the reservoir if I was to pull the leaver, is there any need?

Sorry for the long post, trying the make things clear.

Many thanks in advance.

[The Artist]

OK, those one man bleed things, is it a tube with a valve on the end? If so, put it on the nipple that has been un done about 1/4 of a turn.

Take lid off reservoir.
Top up.
pump brake lots, keep filling up reservoir
NEVER let it run out.
Watch the tube thing and make sure there are no bubbles coming out. If there are, continue.

If there are not, close the bleed nipple and make sure reservoir is full. Put lid back on and go for a test.

As you have done a rebuild, this process may need repeating in the next day or two depending on use.

[map]

Take top of reservoir (make sure turn bars to it's level). Cover with clean cloth to stop muck getting in and then tie brake lever back to the bars (with bungie, gaffer tape, etc.). Leave overnight (or during the day) but try and avoid doing this when the weathers damp/wet (or if you've got a garage no problems).

This forces the air slowly up to the reservoir. Remember to put the top back on

Another tips is to take a rubber mallet and gently tap the caliper to force air up the lines.

Another lace where air gets trapped is the banjo bolt into the reservoir. Crack this open (put a cloth underneath to prevent spilling onto bodywork/paintwork) and then tighten it.

HTH
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[Jai466]

[Jai466]

[Whosthedaddy]

Yep, no bubbles, just fluid.

Repeat, test, repeat again as it may need doing several times of you are having problems as I have had in the past.

[Jai466]

[Jai466]

[map]

[Whosthedaddy]

I believe the answer to be yes.

[Whosthedaddy]

[Jai466]

[Jai466]

Would you guys advice that I can ride my bike... or shall I bleed 1st.

I have already taken the bike for a ride as my 1st post said and it stops.

[Kickstart]

Hi

Personally I would say sort it.

Where are bubbles visable?

One problem can be that when the bleed nipple is undone air can get down the threads and into the caliper. Normally only undoing it a small amount stops this. However might be worth trying again, but pull the lever hard , keep it pulled and then slacken off an retighten the bleed nipple (ie, undo it slightly and allow some fluid / air out but tighten it as the lever reaches the bar so air has no chance to get back in). Repeat that a fair amount.

Also check the bleed nipple is at the highest point on the caliper (assume you aren't trying to use a bleed nipple banjo bolt, normally a bodge people use when they have sheered off the bleed nipple).

As mentioned above it is common to get a bit of air stuck in the top banjo bolt. To get rid of this wrap some cloth around the banjo bolt, pull the lever and crack off the banjo bolt and tighten it again, then you can release the lever.

All the best

Keith
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[Jai466]

[Whosthedaddy]

Google says:

https://www.sideways-technologies.co.uk/images/m2.jpg

I've had bubbles in the tube that may be likened to that of a glass of beer, the more you pump the brake lever, tighten the nipple, top and repeat should start to see less and less bubbles, or even just larger bubbles that are easier to get out of the tubing.

[NiteMare]

right then, do you want a cheap and simple way to sort your problem ??

my way of bleeding stripped and re-assembled front calipers works quite easily and quickly ...

you need a couple of large syringes from your local chemist (50ml) and some snug fitting pipe to connect one to your bleed nipple, fill that syringe with brake fluid and connect to the nipple...

after first sucking all the fluid out of the reservoir with the other one, after of course covering your paintwork with rags to protect it...

leave the res' cap off so you can suck more out as needed...

now slacken the bleed nipple and start injecting fluid in thru there (air goes uphill easier than down), your res' will start filling so keep an eye on it, bubbles may come up as well, once you have some fluid in the res' repeat the process with your other caliper(injecting fluid)....

now at this point you should have no air in the mastercylinder or lines but there may be a little trapped in the caliper still...

so nowyou bleed the brakes using a tube into a jar with a little fluid in it to act as an airlock, bleed as you normally would to get the remainder of the air out of the caliper being careful not to let the res' empty, repeat for the second caliper ....

you now should have shit hot brakes ...

if you still can't get it correct it's time to pay someone that can
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[Jai466]

[Jai466]

[Kickstart]

[Jai466]

Thanks

Should I open the one near the master cyclinder and the calipier only master cyclinder?

Also Keith I know you said that I should not pull the lever all the way but if I do then thats the time wen all the air bubbles come out.

[Kickstart]

Hi

Air gets stuck in the top banjo bolt. Basically you want to have the lever pulled and then crack the banjo off a touch and retighten it (use cloth around it so any fluid that gets squirted out is caught).

There are likely 2 holes in the bottom of the reserviour. There is likely one fairly large hole that allows fluid to get behind the piston. This will be nearer the lever is is pretty irrelevant. There will also be another hole further from the lever that is probably a fair bit smaller. This leads into the useful part of the master cylinder and it is from here that you want no bubbles to come from.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[NiteMare]

[Jai466]

Right guys thanks for your posts.

What I've done is took all the old brake fuild as I found out that my brother shook the bootle before he put in the brake fuild i.e. lots of bubbles.

I kept on pumping the lever untill none was left in the res and opened the nipple.

Top which with new fuild and closed nipple and kept on pumping the leaver untill no air bubble appear from the res.

ATO pressure has bulit up and there are very very small bubbles appear when the leaver is pumpped and held against the bar tight.

I've got a cable tie and held the leaver and handle bar together to let all the remaining air out.

What you guys thing would all the air be gone now?

p.s. You guys rock.

Thanks for all your help.

[rotax81]

apart from all the other techniques above. if there is still a stream of tiny bubbles coming up then i normally start the bike up and let it idle while gently pumping the lever. the vibrations help the bubbles rise.

the normal way i do it is to use an easibleed kit but fit it to each caliper nipple rather than the cap.

mind taking it out if you are unsure of the brakes. they can be unpredictable with any air in there
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