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Any advice on bleeding stubborn brakes

  • Thread starter Thread starter bikerzx7r1981
  • Start date Start date
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bikerzx7r1981

Guest
So ive stripped all the front brakes, fitted the new brake switch and come to bleed the brakes an nadah;)

I took the banjo bolt out of the master cylinder and nothing was coming out of the till i put my finger over it and built up the pressure a bit. so but the botl back in.

I can spits of fluid out of the bleeders but nothing major and not enough to bleed and between the spits of fluid i can here the air pushing so it seems clear so think the problem might lie at the master cylinder.

I cleaned any bits out when i drained the mater cylinder, but not sure if some may have got through. Ive heard there a pain to bleed once dry but any help appreciated... spent two hours and nothing.

cheers all.
 
use a syringe at the bleeder to draw the air out, then the brake fluid, you should be done in 5 minutes.
 
If you have fitted the banjo bolts with the bleeders you will struggle to get the last of the air out as the bleed nipple is no longer at the highest point in the caliper...but there is a trick that helps get over this.

Undo and remove the lower caliper mounting bolt and loosen the upper a tad then swing the caliper until the bleed nipple is at the highest point. Now pop a piece of wood in between the pads to replace the space that is normally filled by the disc then bleed as normal. When all is done just swing the caliper round and tighten up.
 
I had to strap my brake lever back to the handle bar and leave it over night to get mine done right. The syringe still wasn't getting those annoying tiny bubbles through and I found I was wasting too much fluid.

After strapping it over night it was perfect.
 
I had a similar problem and used a hand vacuum pump attached to the bleeder to get the fluid started then it worked fine.
 
My friendly local mechanic will let me barrow a Pump that will fit over the bleeders, and pump the fluid up the hose, allowing the air to go Up(the way it wants to go anyhow). I've used this on my front brakes on my 550, as well as on a clutch master cylinder on my truck. Just filled the pumps reservoir with fluid, and put the hose over the loosened bleeder and pump away, keep going till the brake reservoir is full and tighten bleeder before removing hose. All done, nice and clean too.
 
After a fresh tear down the master cylinder needs to be "primed", or filled with fluid before it will pump. Drawing a vacuum on one of the caliper bleeder nipples sucks fluid out of the reservoir and into the pumping chamber and typically gets things going. You can use a vacuum pump, syringe, or even a long piece of tubing you draw a vacuum on with your mouth (clear tubing helps you watch to make sure the fluid isn't coming up too far if you catch my drift). Once the system starts to pump, then normal bleeding procedures apply.

BTW, make sure the small return port hole is open in the mastercylinder or it will never pump properly. This passage is ultra small and easy to overlook unless you play specific attention to it.
 
Nessism said:
After a fresh tear down the master cylinder needs to be "primed", or filled with fluid before it will pump. Drawing a vacuum on one of the caliper bleeder nipples sucks fluid out of the reservoir and into the pumping chamber and typically gets things going. You can use a vacuum pump, syringe, or even a long piece of tubing you draw a vacuum on with your mouth (clear tubing helps you watch to make sure the fluid isn't coming up too far if you catch my drift). Once the system starts to pump, then normal bleeding procedures apply.

BTW, make sure the small return port hole is open in the mastercylinder or it will never pump properly. This passage is ultra small and easy to overlook unless you play specific attention to it.
Click to expand...


cheers ...Small return port hole, whats that mate? is it the hole just when you press the brake ? how do I make sure its opep
 
bikerzx7r1981 said:
cheers ...Small return port hole, whats that mate? is it the hole just when you press the brake ? how do I make sure its opep
Click to expand...

Neh, you have the big hole that the fluid goes out, and then usually in the reseviour somewhere there will be a lil tiny hole, not much bigger than the point of a needle or so, that's the return port that allows over-pressure to come back to the res such as when the fluid heats and expands, etc. If this isn't clear, she won't pump well, and if she does and you take her out on the road, the calipers will eventually seize from the heat building pressure that has no-where to go but pushing the pistons more.
 
Picture worth 1k words?

Picture worth 1k words?

Lets see if i can get this up
daconover


Master-Cylinder-Cutaway.jpg

You can see that there are 2 holes in the bottom of the reservoir, one is always 'behind' the plunger, one is in front of the plunger until you pull the leaver. This front one is quite small, and can easily be overlooked if clogged with something the same color as the reservoir. Obviously this cutaway drawing is not of a GS MC. But I think you can SEE what he's say'n.
 
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