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No brake fluid movement in MC

  • Thread starter Thread starter eran_k
  • Start date Start date
E

eran_k

Guest
Hi all,
I'm rebuilding a suzuki GSX 400.
Iv'e rebuilt the front caliper and the master cylinder (all with suzuki OEM parts)
i wanted to bleed the system and ran into a problem, no matter for how long i pump the handle no pressure is being built and the fluid doesn't go down from the "cup" to the pump body.
I left the handle "pulled" for couple of hours but it didn't made any difference
i feel no resistance when pumping and the surface of the liquid does not move.

Any ideas?

and just as an option, can i fit a GSXR master cylinder to my bike but stay with my caliper?

Thanks
Eran
 
Have you got all your brake lines plugged in or are you just testing the MC?

The GSXR MC will fit but you'll have to figure out a bracket to hold the reservoir.
 
Remove the brake line from the MC. Squeeze the lever, block the port with your finger, release the lever. Squeeze it again, keeping you finger blocking the port, but if any fluid moves against the finger let it out, repeat as needed. You are basiclly using your finger as a one way valve to let fluid come out but not back in.
 
If you had a syringe and a hose handy you could draw the brake fluid thru the lines from the bleeder and overcome this problem.
 
tkent02 said:
Remove the brake line from the MC. Squeeze the lever, block the port with your finger, release the lever. Squeeze it again, keeping you finger blocking the port, but if any fluid moves against the finger let it out, repeat as needed. You are basiclly using your finger as a one way valve to let fluid come out but not back in.
Click to expand...

That's the ticket. Make sure you cover your paintwork up to avoid splashing with fluid.
 
Tried that, i got little fluid at the MC exit but not a "Flow"
My MC is a one piece unit and there are two holes at the bottom of the reservoir.
thru one i can see the piston moving and that's where the bubbles came from, i guess the other hole is where the fluid is drawn into the cylinder,could it be blocked?
 
It can, and it common is. That's the compensation port, the one that can kill you if it clogs up..

You said you rebuilt the MC???
 
Rebuilding: cleaned it as best as i could inside and out and installed new internals (piston,spring and seals)
i might have missed that hole,is it tiny? (like a very small pinhole)
 
any good method to make sure it's open?
should a hair from a wire wheel go thru the hole?
 
Easiest method I've found is to use a syringe connected to a clear hose, if you have only changed the hose I assume you still have fluid in the caliper, fill the syringe and push out any air bubbles connect to the bleed nipple and undo the nipple (note anymore than half a turn on a bleed nipple can let air back in the system and you'll be at it forever and a day) slowly syringe fluid into the caliper and up in to the MC you will see how much air is pushed up into the MC, repeat a few times, then bleed as normal from the caliper.
This method worked perfectly on my XJR last weekend after changing the hoses.

As stated cover any previous paint work, and don't on mad using the syringe all you'll have brake fluid all over the place.
 
Last edited:
eran_k said:
any good method to make sure it's open?
should a hair from a wire wheel go thru the hole?
Click to expand...
A hair from a wire wheel is probably WAY too big. :eek:

You can examine some of your electrical wire to see if any of them have fine strands. Poking one of them down the hole might do the trick.

One more tip: Before re-connecting the brake line or the handle, use a screwdriver to push the plunger as far as it will go. Sometimes there is a pesky bubble of air that stays at the top of the bore, just inside the outlet to the hose. The piston usually is not pushed very far into the bore, using a screwdriver will push it farther, usually expelling that pesky bubble.

.
 
eran_k said:
any good method to make sure it's open?
should a hair from a wire wheel go thru the hole?
Click to expand...
There are different sizes of wire on different "wire wheels"....
I used a strand from a very-common cheapo wood-handled wire brush. These Wire brushes are good because the wire is stiff and the right size....even a strand from a brass barbecue cleaner brush would not work for me.
 
I just rebuilt my caliper/MC and ran into the same scenario. Remove the handle and use a flathead screwdriver to push the piston; you'll see tiny bubbles coming out that second hole...that's the air being released and fluid making it's way through the line.

I also used a pump you can see in this thread: http://www.thegsresources.com/_forum/showthread.php?t=216696&page=3

It has a reservoir so pumping in wasn't too messy. Take a look at some of the notes eil wrote. Good luck.



Ed
 
If you can't get a wire through the hole keep in mind it might be blocked permanently. I had an MC a few years ago without a hole in that port and needed a machine shop to drill it out. You'll need them as you won't be able to find a bit small enough available in the regular world.
 
Tiniest Hole Ever

Tiniest Hole Ever

Man, that sucks if you have to poke the tiniest hole ever with a wire. The only way I was able to see it was during the time I pumped the brake handle after using the suction tool.

What I did was soak the MC in Safety Kleen for 8hrs.....4 days straight! So any residual elements were washed away. Is this something you would consider?

I had the time because I rebuilt the Caliper & MC and installed a braided line. I will tell you the change has made a GREAT improvement to my stopping power.

It took me several Weeks to complete this task but it was worth the wait.



Ed
 
Torch tip cleaner or the tiny metric drill bits that are for sale on Ebay?
 
Gentlemen, we have braking!
A big syringe and some Teflon tape did the job.
when i started pulling liquid with the syringe i realized the bleeder is not sealing 100%, so iv'e wrapped some Teflon around it and then the air bubble dance relay got going, after sucking about 3 50ml syringes i got just liquid.
the handle feels great and i'll see if it keeps pressure for couple of days before testing on the road.
Again, thanks for all the good advice i got here
Eran
 
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