Ok...so I'm not too bright...but here is what happened:

I was replacing my front brake pads.

removed the caliper from the fork and squeezed  the brakes too see how the pistons work.

when it came time to put the new pads in...in pressed down on the pistons and of brake fluid started gushing out of them.


Here is what I have done so far. cleaned away all the dot4 fluid spilled all over the place.

installed new calipers and remounted on the fork.


What's my next step  :dunno:

I'm going to have to bleed the brakes I'm sure but I have no idea how.

Any help is greatly appreciated...and yes...please make fun of me, as long  as you help me get out of this one


Jonah

Yea pushing in the slave cyl will tear out the seals ... The best bet is to clean the ooutside of the piston before sliding it back ... WD40 and clean with air followed by narrow brush ... its gotta be clean and smooth and oiled ...
BTW you'd have to buy O rings and re build it ... It cannot leak the obviously... and get rid of Dot 4 it will eat paint and hurt plastic and go to Dot 5 ... silicone based fluid ...and get a bleeder pump ... or borrow from raylarrabee If he will give ya ...
Cool.
Srinath.

QuoteBTW you'd have to buy O rings and re build it ... It cannot leak the obviously

Hmmm.... what are the O rings for?

Thanks,

Jonah

The O rings keep the brake fluid in ... Ask someone who's done more calipers ... I am under some sorta memory block ... I did my one and only one back in 97/98 ...
Cool.
Srinath.

Does anybody care to help me with this or know any good pages on the net about this..I'm in LA ...I'll pay you for an hour of labor...get you lunch...we could even go riding if down.

I don't know what the hell..I'm doing...I have a Clymer manual but I can't make any sense out of it.  I'm just trying to bleed the system.  

Jonah

update:

I followed communter guy's technique for draining and replacing the brake fluid.

Now I have to squeeze a lot and it feels very rubbery.
Could that be caused by air in the brake line?  The strenght of the new pads feel fine...just the squeezing feels wrong and has too much travel.

Jonah

put a small pipe on the bleed nipple on the top of the caliper, use an 8mm spanner and loosen the nipple about quarter of a turn, make sure the pipe is soft plastic or rubber, and a good tight fit.

put the pipe in a bottle that has brake fluid in, keeping the pipe immersed in the fluid at all times, stops air going back up.

fill the resovior with fluid,

pump the hell out of the brake lever, fast as you can till it starts to pump fluid, takes a while as they are a pain to bleed, once fluid starts, keep an eye on resovior, so as not to go to low on fluid, keep handle bars straight and do it on the center stand

once the fluid has pumped through one resovior full, then keep lever in and tighten nipple , press lever half a dozen times till its hard, then that should do it.

they are a pain to get the fluid through at first go.

another way is to do the same, but instead of a rubber pipe, use an old bysicle pump, and suck the fluid through, it comes through quik that way, so be carefull and have someone watch and top the fluid up

knowsley,

Ok I did that....it help a little.  The brake lever is a little firmer...but I'm still 80% sure that it travels more and is a little spongy.

I put dot 4 automotive oil in the brakes...that shouldn't make a difference, does it?


Also...when I squeeze hard I hear a tiny little  sound coming from around the caliper area. Like a little tiny, farting bubbly sound.  :mrgreen: sorry not the best description but that's all I could think of.

Jonah

do you get the noise when stood still or when braking as you are on the move, if its when you are stood still there must be still air in the system, especially if its still spongy, check to make sure those calipers are not leaking or a piston is not seized

Quote from: VersOneI don't know what the hell..I'm doing...I have a Clymer manual but I can't make any sense out of it.  I'm just trying to bleed the system.

Well Jonah, when you work your way through this, you will have experience for the next time. I applaud your willingness (or curiosity, or poverty, or masochism) to attempt this critical, but manageable task.

At this point, assuming you have no leaks or puddle forming, it sounds as though you are only dealing with air in the system. If you remember your physics, the reason the brake feels spongy is because you can compress a gas (not the fuel type), but not a liquid. You will have to bleed the brake system until it is free of air (gas). Do it again, recyle the fluid (new clean), then do it until NO BUBBLES emit from the drain tube.  BUBBLES = BAD

It sounds like you are relatively new to self wrenching. The Clymer manual is best for experienced wrenchers. For you, I recommend the Haynes. The procedures are very well photographed and many pictures are in color.

I usually have my buddy check over and help with with my work...he has taken many bike repair classes.

Just me and Clymer this time...


So I'll bleed the brakes again, although I'm 90% sure I did it right.
Re-check the calipers for leaks and pistons.  I'll go real slow double check everything.

Starwalt: I would say...99% poverty 1%curiosity.
which brings me to the following question: how much would a bike shop charge me if I took it in right now too have them use a bleeder pump and get the air out (assuming that's what it is)


Respectfully,

Jonah

Bleeding The System

Open the bleed nipple slowly - you should only need half a turn and at the same time slowly and smoothly squeeze the brake lever in (or push the brake pedal down). Hold the lever in and you should see air bubbles or fluid being expelled into the jar. Old brake fluid looks foul and can be any colour from dirty white to brown or black. Movement of fluid and/or bubbles will continue for a second or two, close the nipple and then release the brake lever. Check the fluid level in the reservoir and top up if necessary. Repeat this operation until no more bubbles appear and the fluid coming out is clear.

If you have a twin system repeat this process with the other caliper (it's best to do the furthest away from the master cylinder first) If everything has gone okay you should now have a brake system with a good solid feel to it, the lever will travel a short distance and then a solid resistance will stop it moving any further.

If when you continue to apply pressure you get a slow movement or spongy feel to the lever it's a good sign that there is still air in the system. There are a number of possibilities not least that you didn't get all of the air out of the system so you should start bleeding again. Tighten all parts to the correct torque setting and then check the whole system to see that the lines are not trapped on full lock, no fluid leaks from anywhere etc

Troubleshooting

Not all calipers have there bleed nipples at the highest point on their anatomy. This means that if there is a small pocket of air trapped above the nipple it will be hard to remove (air always goes to the highest point of the area it is in) and make the system spongy. You can get around this by taking the caliper off and making sure the nipple is at the highest point but remember to put a spacer in between the pads to stop the pistons popping out and making it easier to refit the caliper.

A similar problem occurs with some racing bikes which have steeply angled handle bars - the brake hose arches up above the master cylinder and a small pocket of air can get trapped here. Again you can rearrange the layout or you could inject brake fluid using a syringe very carefully and slowly in through the bleed nipple in the caliper bearing in  mind that the fluid in the reservoir may overflow. Fitting a banjo bolt which incorporates a bleed nipple to the master cylinder and bleeding this first before the rest of the system is another way to fix this problem.

If you are unable to remove the sponginess no matter how carefully you bleed the system you may have a sealing problem which you will need to consult your local dealer about.

The master cylinder is fed from the reservoir by a tiny hole and this hole easily gets blocked which is why cleanliness is so important when bleeding brakes. If you cannot bleed your brakes yourself make sure you talk to your local dealer and get them to do it for you.

Don't be tempted to use any of the 'self bleed' gadgets unless you really, positively, nothing else for it, have to. These things allow the nipple to be kept open as they incorporate a non return valve to stop air re-entering the system. But the bleed nipple has a threaded end which screws into the caliper - air can be sucked into the caliper along this route if the nipple is loose in the threaded part of the caliper - it will only be a small amount but why do it in the first place as we are trying to remove air...

When you have successfully bled your brakes make sure both bleed nipples are done up tightly, all banjo bolts are done up tightly and top up the reservoir. Do not overfill the reservoir as this can cause hydraulic locking of the system preventing the pistons in the caliper from fully retracting - this causes binding of the brakes.


Re check the system visually before test riding - and we mean test riding. Just go forward a few feet slowly and apply the brakes then bring the bike back into the workshop to check that their is no fluid leaking from the system, everything is done up correctly and the brakes have a good solid feel to them.

Quote from: VersOne... how much would a bike shop charge me...

That would vary by market and business owner. You could pick up the phone book and let your fingers do the walking, but at the very least expect minimum shop charges of one hour, maybe even two.

Those people are in the business to make money by wrenching. Even when they do warranty work on a bike they sold, it gets charged back to the OEM, albeit at a reduced rate from what you would pay in a no warranty situation.

Cycle shops, like auto repair shops, come in all flavors. A reputible shop will call you with costs before doing anything to the vehicle that you did not previously instruct them to do.

thank you so much for all the input.

I had somebody top up the fluid for me while I handled the rest...made the whole job much easier.

I even took it to my local bike shop and one of the guys there offered to take a look at it for free.  He told me the system was fine..which is reassuring.

I'm glad I did, it was a good learning experience.  I ordered a back brake pad too...so I will be able to change that one too when time comes.

Thanks too all you GS mechanical gurus.

Jonah