Trying to bleed brakes -- no pressure from master cylinder

Sackmonkey

New Member
Hello all,

I've been a daily lurker for a long time, but this is probably my first actual thread. I've learned a ton from you guys over the years, but I'm stumped on this one.

I did the R6 fork swap onto my 2006 FZ6. The swap went super smoothly (I still need to fashion some fender tabs), but I can't get the brakes bled. In addition to installing the R6 calipers, I also put on a new set of stainless brake lines. Since there is now a dedicated line for each caliper, there is no loop over the fender to get air stuck in. I've filled the MC with fluid and can't get it to make pressure no matter what I do. I've tried every combination of leaving the bleeders open, closed, and even disconnected the banjo bolts from the calipers to let some fluid gravity drain through the line (it dripped out the right side, but just a few drops came out the left).

I have a lot of experience with track days in my cars, so it's not like I'm new to bleeding brakes. I double checked and all the (new) copper washers are in place also. I'm wondering if it could be the piston seals, or maybe a defective brake line? But still, it seems to me like I'd hear some amount of pressure squiring out the leak, right? The system seems completely tight, but the MC just isn't making any pressure. Is there a hidden bleeder somewhere?

Am I more likely to prime the MC with the cap installed, or leave it off? I've tried both ways.

I also installed new pads and the pistons seemed to slide back really smoothly when I put them in.

I have a Mityvac hand pump *somewhere*, but I can't seem to find it. I hate to go buy another tool I already own (and I always thought was junk anyway), but I'm not sure what else to do at this point. Last night, I left the handlebars turned left and put a zip tie on the lever to hold it open (with the MC cap installed), but it didn't seem to make a difference this morning..

I still have to install the rear stainless steel line and I'm wondering if my process could've avoided this?

Any suggestions? I think it's funny that I was a little nervous about doing the fork mod, but it was something as simple as bleeding the new brakes that actually caused me all the trouble.

Thanks for any help,

Rob
 

Motogiro

Vrrroooooom!
Super Moderator
Moderator
Elite Member
I would first suspect the MC in this case. The master cylinder is serviceable. I have a cheapo Harbor Freight vacuum that I use that get's the job done for me I use it on my hydraulic clutch as well as bike a
vehicle brakes.
It could be there is so much volume to fill with air in it that the MC pump piston does have the volume to make a difference so you may need to vacuum it down.
 

trepetti

It's all good!
Elite Member
Site Supporter
Hello all,

I've been a daily lurker for a long time, but this is probably my first actual thread. I've learned a ton from you guys over the years, but I'm stumped on this one.

I did the R6 fork swap onto my 2006 FZ6. The swap went super smoothly (I still need to fashion some fender tabs), but I can't get the brakes bled. In addition to installing the R6 calipers, I also put on a new set of stainless brake lines. Since there is now a dedicated line for each caliper, there is no loop over the fender to get air stuck in. I've filled the MC with fluid and can't get it to make pressure no matter what I do. I've tried every combination of leaving the bleeders open, closed, and even disconnected the banjo bolts from the calipers to let some fluid gravity drain through the line (it dripped out the right side, but just a few drops came out the left).

I have a lot of experience with track days in my cars, so it's not like I'm new to bleeding brakes. I double checked and all the (new) copper washers are in place also. I'm wondering if it could be the piston seals, or maybe a defective brake line? But still, it seems to me like I'd hear some amount of pressure squiring out the leak, right? The system seems completely tight, but the MC just isn't making any pressure. Is there a hidden bleeder somewhere?

Am I more likely to prime the MC with the cap installed, or leave it off? I've tried both ways.

I also installed new pads and the pistons seemed to slide back really smoothly when I put them in.

I have a Mityvac hand pump *somewhere*, but I can't seem to find it. I hate to go buy another tool I already own (and I always thought was junk anyway), but I'm not sure what else to do at this point. Last night, I left the handlebars turned left and put a zip tie on the lever to hold it open (with the MC cap installed), but it didn't seem to make a difference this morning..

I still have to install the rear stainless steel line and I'm wondering if my process could've avoided this?

Any suggestions? I think it's funny that I was a little nervous about doing the fork mod, but it was something as simple as bleeding the new brakes that actually caused me all the trouble.

Thanks for any help,

Rob
I had the same problem when I installed my SS lines, when I rebuilt my S1 calipers and when i installed my R6 forks. I was never able to push fluid down so resorted to pulling. I use a Mytvac to suction bleed, but have also used the syringe method and the suction bleeder used with an air compressor. Pick one of those and it should be a piece of cake.

Sent from my SM-G930V using Tapatalk
 

TownsendsFJR1300

2007 FZ6
Site Supporter
Can we assume the master cylinder is the original AND WORKED before the fork change?

If so, I agree, sucking from the calipers should work, it's how I've always done it.

Also, if the master as completely dry and now full, pull the lever back and forth and you should see air bubbles coming out of the bottom orifice (where the plunger resides). You have to get all the air out of there.

*As activating the brakes takes a pretty pull of the lever for a full stop, that cylinder is pushing VERY LITTLE FLUID when you try to prime the system.


I do use a Mityvac, but the better aluminum one (that also can pressurize), (a step or two above the plastic units)..

I leave the cap off the master cylinder when bleeding, only because the Mity vac will suck it dry in three or so "pulls" and you don't want it running dry on ya... Crank up the pressure at the caliper, crack the bleeder, then close it before ALL the vacuum is gone.

Dumb question but have to ask, the bleeders are facing upwards on the calipers, correct?
 

Sackmonkey

New Member
Thanks to both of you for your comments. I definitely don't think it's the MC since it was working up until the minute I drained it. I'll break down and buy yet another vacuum pump to pull the fluid into the system (then properly bleed it using pressure afterwards). Thanks for the Harbor Freight idea.. I hadn't considered them!
 

FinalImpact

2 Da Street, Knobs R Gone
Super Moderator
Site Supporter
I'd say it is your method.
The stroke volume of the MC is just a couple of cc's.

Also, pulling the lever to the bars seals OFF the feed port from the reservoir. This is the exact opposite of what you want to do on a fresh install.

If it were mine: fill the reservoir.
Connect a large volume syringe to an open bleeder (no more than 1/2 turn open).
Pull back on syringe. Seal bleeder. Check fluid level. Fill as needed.
Repeat until there is a direct relationship of fluid extracted to MC fluid drop.
Repeat on the other side.

Once done, read tips below about tapping on the caliper for a firm air free system.
This whole process should take no more than 10min to do both sides.

JM2C but the mitty vac is over rated. Buy some 500cc petroleum grade syringes. These are direct action no messing around.


Link to troubleshooting and maintenance activities.
https://www.600riders.com/forum/fz6-technical/52536-troubleshooting-maintenance-guide-fuel-pump-battery-charging-brake-bleeding.html

Brake Bleeding....
https://www.600riders.com/forum/fz6-technical/52536-troubleshooting-maintenance-guide-fuel-pump-battery-charging-brake-bleeding.html#post593693

<< PASTE >>
***********************************
BRAKE BLEEDING, CALIPER AND PAD INSPECTION
***********************************


First off; bleed your brakes annually! Why? The OEM DOT 4 fluid is an ether glycol product which absorbs moisture at nearly twice the rate as DOT3 fluid. These fluids are hygroscopic and absorb moisture which breaks down the hardware as it converts into acids. In addition, moisture in the system reduces the boiling point (may boil over) and can induce brake drag as the pistons do not retract as effectively when there's moisture or air in the system. Granted, new synthetic fluids withstand this better than old ether - glycol based fluids, it just makes good sense to inspect the entire system and bleed the brakes annually.


The process I use to bleed brakes:
Tip number one - buy a syringe and some soft tubing. Preferred is silicone as it can stretch to any size fitting you might encounter and it very pliable. When it comes time to do a brake flush, simply suck out the old fluid, clean out the reservoir and dump in the new DOT 4 fluid. Note: A turkey baster will work to remove old fluid too. Our goal here is to NOT MIX old and new as its more fluid to pump out.

  • NOTE: Always use Fluid from a NEW UNOPENED CONTAINER!!!
    The reason being, once the seal on the container is broken, the fluid begins absorbing moisture. Also, If it possible, perform brake repairs/bleeding on low humidity days!
    PROCESS:
  • Crack the bleeders to insure they can be loosened and then snug them down FIRM. Fit a long section of hose to the bleeder and into drain pan.
  • Clean MC lid, remove it, remove old fluid (clean inside and seal if dirty). DO NOT PUMP lever when fluid is removed....
  • Fill MC w/FRESH FLUID, install cap/lid.
  • Pump lever/pedal and hold lever down with pressure.
  • Crack the bleeder and continue applying pressure to lever. When the lever bottoms, seal the bleeder promptly.
  • Repeat above steps until clean fluid is coming out. WATCH THE FLUID LEVEL! Don't allow the level to get low or it will force air into the lines!
  • Do both sides if applicable.
  • On the final bleed (both sides), seal the bleeder before the lever reaches bottom. This prevents air from entering the system.
  • Fill MC to correct level, install lid and clean everything spotless!
  • Repeat once a year using NEW DOT 4 fluid!

NEW LINE INSTALL:
If you've installed new lines and have allot of air in the system, use the syringe and open a bleeder. Connect the syringe and pull back on the plunger to pull fluid through from the reservoir.
- BEGIN AT BULLET SECTION above to obtain a firm lever!

Use a syringe to remove old fluid! It's way better than pumping it through!


If you have a long hose, run it straight into a pan or bottle. Here I was in pinch and just let it fill up the syringe.



  • Do not get brake fluid on anything as it eats paint and will/can dull powder coated items too.
  • ** DO NOT LET THE MC reservoir go empty and suck air or your brakes will be all mushy and you'll have to start the bleeding process over!! **

***********************************

Additional tips:
IMO Vacuum bleeding never gives a solid feel. Pressure bleeding forces the trapped air under pressure to condense into larger bubbles. As the bubbles increase in size, they often move to the top where the bleeder is and can be removed.
To assist the trapped air bubbles in making their way out of the brake system, use a dead blow hammer or a firm block of wood and tap on the caliper striking towards the ground. DO NOT TAP INLINE WITH THE CALIPERS PISTONS ESPECIALLY on FLOATING CALIPERS! If you choose to tap that way, do so gently you can damaged the disc and induce air into the system. This small shock (hammer tap) can remove trapped air bubbles. The momentary shock helps them condense and make their way out of the caliper. Don't leave marks or damage anything. Your tapping too hard if this occurs!

Note: The rear of both S1 and S2 FZ6's are floating calipers. The front of the S2 models are fixed 4 piston calipers. S1 front calipers are floating calipers.

***********************************
Brake Pad Replacement:

As brake pads wear, the pad backing and calipers piston move towards the rotor. With the piston out of the caliper it attracts and retains brake dust.
BEFORE SHOVING THE PISTON BACK INTO THE CALIPER and TRAPPING the ABRASIVE BRAKE DUST IN THE SEAL, CLEAN THE PISTON(S)!!!
The dust seal can only stop so much from getting past it! To extend its life and reduce wear use an old paint brush and rag & brake cleaner to clean the pistons. To get behind the piston on the S2 front caliper, use the brake lever to extend the piston. Use a shoe lace to scrub the back of the piston! When they are clean and free of debris, push them in and move on to the next one. Mine all push with my thumb. No tools were needed to force them inward. You do need to STOP fluid movement tho (Lock the Pistons).


Locking the Pistons out:
First, pull the lever a bit and get a couple pistons out. Then tie the lever down so it seals the bleed port. Now when you push in a piston, one or more will pop out because the fluid can not return to the MC!


Wipe the brake dust off. A horse hair paint brush, cotton towel, and shoe string work great for this:


No you don't have to use your feet! lol :
Hold the Shoe String against the piston on one side (while holding the caliper in same hand) and pull on the string with the other hand. WALLA! That narrow crack covering the piston is now clean. If you must, saturate the string with brake cleaner and give it tug! It works great!





When done cleaning:
- Crack the bleeder and push all four pistons in.
- Seal the bleeder and release the brake lever.
- Install pads and insert pins. Pump lever to build pressure and hold the pads in place.


Remove the pin and drop in in the anti-rattle clip. Insert the pin & keepers and its on to brake bleeding.
For Rear and Front S1 calipers, the sliding caliper pins should be cleaned and inspected for wear. The slides need greased before new pads are installed.​
ALSO: Seals do wear out / get hard.
OEM Suggested Replacement interval:
Brake Pads: If necessary
Piston Seals: Every two years
Brake Hoses: Every four years
Brake Fluid: Every Year

NOTE: Anti-rattle clips points forward!

FRONT:
Brake pad lining thickness inner & outer pad: 4.5 mm (0.18 in)
Discard Limit: 0.5 mm (0.02 in)
S2 Caliper Bolt Tq: 29ft/lbs, 40Nm
Banjo Bolt: 22 Ft/lbs, 30Nm
Bleeder Tq: 4.3 in/lbs, 6Nm

Disc Thickness:
Disc Discard limit: 4.5 mm (0.18 in)
Brake disc deflection limit: 0.10 mm (0.0039 in)

***********************************
Checking Rotor Defection:
***********************************

I'm not going to go into detail on this but if the wheel leaves my sight I inspect it. Its MY LIFE AT STAKE and I trust very few with my life!

Hint: Wheel was off and out of my sight for tire replacement so I thought it worthwhile to check rotor trueness upon installation just to confirm nothing happened that I was not aware of.

Brake disc deflection limit:
0.10 mm (0.0039 in)

Measured
Inner - Outer radius:

RS = 0.0002 - 0.0004" Less than 1/2 distance between marks.
LS = 0.0008 - 0.0013"

Each mark is 0.001" so its within spec! Steel Quick Clamp in combination with the axle bolt made the Magnetic Base on the dial stay put! :thumbup:


Needless to say the sun was evil and with a white dial, didn't stand a chance of getting a clear photo of the setup and read the dial.
LS outer....


In short, you need the proper tools for the job. In this case, I improvised creating a base and getting the needle square to the rotor so the inner and outer edge could be checked for trueness.

***********************************

Edits:
2016-02-27 restored pictures
 

bigborer

Member
I've had the same issue a few times, so I understand your frustration.

When you normally use the brakes, you only use a part of the MC cylinder's stroke. The other part is not used and might get gunk and oxidation on it. Now you use the full stroke of that piston while trying to bleed the brakes and get the (already old) seals rubbed on the nasty part of the cylinder...

Only solution for this is a installing a new rebuild kit for the MC. Do not ride with your current MC seals! Even if you manage to get a bit of pressure with the aid of syringes or vacuum pump, you still have bad seals and will likely lose pressure after a while... Been there, done that... Not the best feeling in the world to suddenly realize that you have the brake all the way down but the bike is only barely slowing down a bit.
 

weehe

Junior Member
All I can add is that it took me what seemed 200+ pulls on the lever to build up pressure when I replaced my lines. I thought I had a bunch of air in mine but it eventually built up pressure.
 

Sackmonkey

New Member
I'm finally home from business travel and fixed my brakes yesterday. Since everyone took the time to help me with suggestions, I figured I owed you guys an update.

While away, I ordered another vacuum hand pump kit from Amazon. This one came with a nice carrying case, so hopefully I won't lose it!

I had previously pulled each banjo bolt at the calipers and let them get to the point where they were dripping steadily. With everything all bolted back up, I started bleeding using the vacuum. I pulled 30 inches of vacuum and couldn't get a drop out! Finally, I slapped myself in the forehead and realized that I wasn't loosening the bleeder enough. I'm not sure why, but that one bleeder was different / longer than the rest and took a full 1 1/2 turns before it was open! Normally, you only need a quarter turn or so (as was true of the other R6 front caliper and the rear stock bleeder).

Once I realized my stupid mistake, I pulled some fluid through the bleeder, then was able to pressure bleed everything as you'd normally do. I got all the bubbles out and also swapped the rear line to stainless and bled that one. BTW, removing that reservoir cap for the rear fluid is huge pain!

All the fluid that came out was pretty clear, which surprised me, so maybe the previous owner actually bled them at some point. But the fluid had a definite stink to it, so I think replacement was probably overdue.

I rode for a few hours yesterday and all seems well. Once it warms up a little more, I'll re-bleed again as I'm sure there will be a few more bubbles to get out. The new EBC HH sintered front pads make a cool hum when you use them (only audible if I have my helmet visor open). The braking power with the R6 calipers and new pads is AMAZING. The suspension swap.. well, I guess I should put that in another thread..

Thanks again guys!

Rob
 

TownsendsFJR1300

2007 FZ6
Site Supporter
That one bleeder screw must have been machined incorrectly.... And would definitly cause issues bleeding..

Maybe order another one when you later order parts.

That'd be a PIA to bleed turning it 1.5 turns...


And thanks for the update!
 
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