bleeding front brake problem

5319 Views 26 Replies 13 Participants Last post by mikebamy, May 31, 2012

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Discussion Starter · Feb 25, 2011

hi all, i have just completely changed out the front and rear brake systems (calipper/master rebuilds and SS lines).

i did the rear first and all went good ,bled the brake to a firm firm peddle.

now i have done the fronts and i cant get any pressure at the lever, i have fluid without bubbles from both calipers but the pistons are not moving at all.

no leaks .

i made a sleeve to push the piston thro in the master cylinder ,so i dont think the sleal has turned over.

and i put a 3/4 block on the grip to stop overtravel as per the manual.

any help would be appreciated.

cheers mark.

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CXTURBOBOOST

· #2 · Feb 25, 2011

Hi..

This doesn't make sense... If you have fluid moving, that is what moves the pistons... If the calipers are both bled correctly and the bleed screws are snug, you should have no problems.. Are you sure you have good fluid through the calipers with air gone?

PK

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Discussion Starter · #3 · Feb 25, 2011

CXTURBOBOOST said:
Hi..

This doesn't make sense... If you have fluid moving, that is what moves the pistons... If the calipers are both bled correctly and the bleed screws are snug, you should have no problems.. Are you sure you have good fluid through the calipers with air gone?

PK

hi pk ,as sure as i can be but i had no air bubles in the fluid where as in the rear set up i got air and fluid in spurts at first then the pedal firmed up , then slowley less air to a good peddle.

but i dont have a mityvac so i just sucked on the bleed tube until i got fluid showing.

but with the fronts no bubbles just fluid ,and no lever preesure.

confussed mark.

CXTURBOBOOST

· #4 · Feb 25, 2011

CX650FAN said:
hi pk ,as sure as i can be but i had no air bubles in the fluid where as in the rear set up i got air and fluid in spurts at first then the pedal firmed up , then slowley less air to a good peddle.

but i dont have a mityvac so i just sucked on the bleed tube until i got fluid showing.

but with the fronts no bubbles just fluid ,and no lever preesure.

confussed mark.

If you close both bleeder screws you should start to get firm handle. Then you can open it after a firm grip and release some air. Then close the bleeder again before pumping up and alternate to the other side..

PK

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Discussion Starter · #5 · Feb 25, 2011

CXTURBOBOOST said:
If you close both bleeder screws you should start to get firm handle. Then you can open it after a firm grip and release some air. Then close the bleeder again before pumping up and alternate to the other side..

PK

i opened the resevoir and it was down a bit ,so i topped it up and tried the bleeders again a bubble from one side and nothing from the other and still no pressure at the lever .

do you think the 3/4 block on the grip is adding to the problem i was thinking about removing it as i was pumping the rear pretty hard with my gorilla foot (no restraint there.).

cheers mark

CXTURBOBOOST

· #6 · Feb 25, 2011

CX650FAN said:
i opened the resevoir and it was down a bit ,so i topped it up and tried the bleeders again a bubble from one side and nothing from the other and still no pressure at the lever .

do you think the 3/4 block on the grip is adding to the problem i was thinking about removing it as i was pumping the rear pretty hard with my gorilla foot (no restraint there.).

cheers mark

Explain the procedure to me that you are using? Are you closing the bleeder screws and then pumping up the master cylinder to pressure? Once pressure you can open one side of the bleeder screws while holding the pressure on the handle. Then close the screw before letting up on the brake lever. If you truely have no air in the system something doesn't make sense. I don't think you have fluid all the way through the system. If you truely have fluid you should get a brake pedal with the bleeders closed.

[email protected]

Discussion Starter · #7 · Feb 25, 2011

CXTURBOBOOST said:
Explain the procedure to me that you are using? Are you closing the bleeder screws and then pumping up the master cylinder to pressure? Once pressure you can open one side of the bleeder screws while holding the pressure on the handle. Then close the screw before letting up on the brake lever. If you truely have no air in the system something doesn't make sense. I don't think you have fluid all the way through the system. If you truely have fluid you should get a brake pedal with the bleeders closed.

yes thats what i am doing, both bleeders are clossed and i have no pressure at the lever no matter how much i pump the lever, i did push the calliper pistons a long way in to make fitting the new pads onto the rotor easier.

is it possible to push them TOO far in??.

thanks mark.

i will have to carry this on tommorow (bed time).

night night.

ramprat06

· #8 · Feb 25, 2011

Doing mine a while back was frustrating for Wootersen and I too. But we eventually got it. Granted it was just a single rotor CX custom, but the theory should be the same. I found a youtube that gives a fair view of how it is done. I would have been more explanatory myself, but at least the visual will take you in the right direction.

[media]http://www.youtube.com/watch?v=09peSQc9ROI[/media]

showmedude

· #9 · Feb 25, 2011

CX650FAN said:
i opened the resevoir and it was down a bit ,so i topped it up and tried the bleeders again a bubble from one side and nothing from the other and still no pressure at the lever .

do you think the 3/4 block on the grip is adding to the problem i was thinking about removing it as i was pumping the rear pretty hard with my gorilla foot (no restraint there.).

cheers mark

Mark,

I too spent a lot of pumps on trying to bleed the front brakes on my GL650. The traditional bleeding process of building up pressure and opening the bleed valve to get rid of air doesn't seem to always work when you've had the system completely apart. Too many places for air and not enough oomph in the master cylinder, I guess. Even though I couldn't believe it, I had an air bubble in the system and fluid at both ends. The best luck I had was to "back bleed" the whole system with a syringe in the bleeder valve. Instead of a syringe, next time I'm going with my buddy's suggestion to rig a small pump oil can of fluid with a hose between it and the bleeder valve to force the fluid in from the bottom and the air out the master cylinder. It's more trouble, but I think it's foolproof when a thousand licks on the pedal/lever don't get you any pressure. Obviously, keep an eye on the master cylinder to make sure you don't overflow it onto something expensive.

Regarding the block to prevent excessive piston travel in the MC, I couldn't see how removing it could harm anything, but I also don't think you are getting any more fluid pushed, just a little further push. If you can back bleed them, it won't matter since you don't use the lever to move the fluid and push the air.

Dude

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Salty1960

· #10 · Feb 25, 2011

The Video doesn't actually show the bleeding process!

If you have a plastic tube fitted to the caliper, the bleed open(good if it is tight on the threads, or not too far open so that air doesn't suck back in), start topping up the master cylinder. Pump the lever as much as you like to start the fluid going. (watch out for squirts out of the reservoir) keep topping up the reservoir and when you have pumped plenty through the line revert back to the traditional technique. (squeeze, squeeze and hold - - loosen the bleed screw- - watch for air - - lock up the bleed screw, then release the lever)

A couple if taps(handle of a screw driver) to free bubbles doesn't hurt to get the master cylinder going, and I always give the caliper a tap to get the final bubbles dislodged from inside ( I only do this in the final few stages of bleeding each cylinder)

This technique has worked for me on cars, go karts, and motorbikes for decades.

Rarely the master cylinder requires more persuasion. (air pressure from plastic bottle / compressor etc)and only when it has been completely cleaned and not lubed with fluid on assembly.

The technique although risking spills of fluid, allows you to see the mastercylinder working (or not) and i have found helps you to know what is happening. (ie is the fluid back flowing in to the reservoir after pumping?)

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DavidfromWisconsin

· #11 · Feb 25, 2011

This is something I wrote up for those I have mentored in the past ...

Brake bleeding

I have done a lot of brake bleeding. I have found problem bleeding the brakes several times. My solution to the problem has always worked for me. Even using a vacuum bleeder I have had this problem.

First off you want all the plastic and painted areas off the bike or covered with the contractor’s thick plastic bags so no brake fluid can get on anything. Make sure you are constantly checking the brake fluid level so you don’t have to start this all over if the master were to go dry.

Take apart the connection right at the master cylinder. Put one thumb over the banjo bolt hole and begin pumping slowly. When the brake fluid begins to squirt past your thumb reattach the hose and banjo bolt.

Go to the next connection which is the splitter on the on some bikes. Disconnect the hoses that go to the calipers at the splitter and put your finger over both sides. Make sure that fender is covered. Again pump until the brake fluid starts to squirt past your fingers.

When it does squirt, reconnect your hoses. With one hose connected and the one bleeder closed, bleed the disconnected hose with your fingers over the end until fluid is running through. Then bleed the caliper on the bled side.

Then disconnect and bleed the hose on the other side. When you have fluid there, begin bleeding the caliper on that side.

Yes, it is a long, drawn out procedure … but it has never failed to do the job.

Finally, I must add, if you use a vacuum bleeder always re-bleed the caliper without the vacuum as the last step, as the vacuum bleeder often pulls air through the threads on the bleeder screw and if you don’t pump that last little bit of air out it will remain in the caliper.

Let me know if this works for you like it has for me …

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Dan Tenn

· #12 · Feb 25, 2011

I had to use a bleeder vacuum when I added stainless lines to my bike. Pretty cheap and turned a two day debacle into a ten minute job.

DavidfromWisconsin

· #13 · Feb 26, 2011

Dan Tenn said:
I had to use a bleeder vacuum when I added stainless lines to my bike. Pretty cheap and turned a two day debacle into a ten minute job.

Just to clarify ...

A vacuum bleeder is the way I normally bleed brakes also, but once in a while not even a vacuum bleeder will do the job for some reason.

But, when using a vacuum bleeder, unless you use something to seal the threads on the bleeder screw, you are usually sucking some air down the threads.

To eliminate that last tiny amount of air (sometimes a large amount of air) forcing the last bit of air is best accomplished by pushing the fluid rather than sucking it out of the caliper.

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CXTURBOBOOST

· #14 · Feb 26, 2011

David from Wisconsin said:
Just to clarify ...

A vacuum bleeder is the way I normally bleed brakes also, but once in a while not even a vacuum bleeder will do the job for some reason.

But, when using a vacuum bleeder, unless you use something to seal the threads on the bleeder screw, you are usually sucking some air down the threads.

To eliminate that last tiny amount of air (sometimes a large amount of air) forcing the last bit of air is best accomplished by pushing the fluid rather than sucking it out of the caliper.

I use mity-vac..

10 minute job. I've never had a problem with air on any of my CXT's as long as the hose going to the mity-vac seals good to the bleeder...

However... I've heard of people fighting it for days when using nothing but gravity..

PK

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homerrod

· #15 · Feb 26, 2011

Most likely air is trapped in the master cylinder piston bore, and it needs to be removed, before doing any of the calipers. You need to "bench bleed" the master cylinder first. Just disconnect the banjo bolt & line from the master, route a hose inside the reservoir, and pump until no air bubbles are present. As you are pumping the lever, tap the side of the master cylinder with a screwdriver handle, wood dowel or small wood/plastic/rawhide mallet, this will help release the air. Here is a link, specific to a car master cylinder, but gets the point across: http://www.tegger.co...chbleeding.html

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Discussion Starter · #16 · Feb 26, 2011

Thanks to all that offered advise ,it was a combination of air in the mastercylinder and trapped air in the right calliper.

i got a "Mityvac" which made it much easier on my own.

but once i got the mastercylinder cear of air that was half the battle.

i did as sugested and went thro all the conections .

and then the vac on the calipers and a finnal purge the old fashioned way .

and now have great stoppers .

i think one of the bleeders is somewhow damaged or malformed on the seal face so i will order a new pair.

many thanks again mark.

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arydberg

· #17 · May 11, 2012

I replaced one of my bleeding screws from a standard ( old fashioned) auto parts shop.

JK McDonald

· #18 · May 11, 2012

Like several others have pointed out, you definitely have air in your front brake master cylinder. I’ve found the angle of this brake assembly on many bikes can be a real problem sometimes.

The procedure that often works best for me is to split a couple of trash bags open and use masking tape to hold them in place to protect the instruments, fairing, gas tank and engine. Have an assistant (or a willing wife) hold the handle bars steady. Remove the cover off the master cylinder so you can visually maintain the correct fluid level. Get an old T-shirt and wrap it carefully around the area of the banjo connector and electrical cables. Then just barely crack open the banjo connector on the master cylinder brake line and very gently apply the front brake lever. Hold it down while snugging back down the bandjo connector. Repeat this until the air is expelled. Once the air bubble has been worked out – the front caliper will go smoothly.

Good Luck, Michael

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CXTURBOBOOST

· #19 · May 12, 2012

JK McDonald said:
Like several others have pointed out, you definitely have air in your front brake master cylinder. I’ve found the angle of this brake assembly on many bikes can be a real problem sometimes.

The procedure that often works best for me is to split a couple of trash bags open and use masking tape to hold them in place to protect the instruments, fairing, gas tank and engine. Have an assistant (or a willing wife) hold the handle bars steady. Remove the cover off the master cylinder so you can visually maintain the correct fluid level. Get an old T-shirt and wrap it carefully around the area of the banjo connector and electrical cables. Then just barely crack open the banjo connector on the master cylinder brake line and very gently apply the front brake lever. Hold it down while snugging back down the bandjo connector. Repeat this until the air is expelled. Once the air bubble has been worked out – the front caliper will go smoothly.

Good Luck, Michael

I strongly suggest dot5 when doing a break rebuild then none of the "covering stuff up" is necessary... Unless you are riding the CXT on a track (hope you aren't anymore) dot5 performs fine and won't harm paint...

PK

DavidfromWisconsin

· #20 · May 12, 2012

CXTURBOBOOST said:
I strongly suggest dot5 when doing a break rebuild then none of the "covering stuff up" is necessary... Unless you are riding the CXT on a track (hope you aren't anymore) dot5 performs fine and won't harm paint...

PK

PK,

Do you mean DOT 5 or DOT 5.1??? Dot 5 is supposed to be the silicone that can wreck older rubber parts.

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