Brake trouble

Hello,
Having some trouble with my front brake. I just rebuilt the caliper and mc and the brakes are still soft. I'm planning on vacuum bleeding them which hopefully should fix it but I noticed fluid pushing through the reservoir gasket when I squeeze the lever. I realize I should replace the gasket and clean the fitting but I'm concerned about the pressure that's building to push it through. There's no reason there should be pressure in the reservior is there?
Thanks!
Ken

 

no, shouldn't get any pressure in the reservoir part.
did you over fill it,
when you rebuilt the master cylinder, did you replace the seals? and did you put them on the correct way round?
did you clean out the tiny holes in the bottom of the cylinder?
stu

 

Yes, I replaced the deals correctly and cleaned the relief hole. The fluid level is a little high, but would that cause pressure? Either way, I'm hoping to get to work on it tonight so I'll bleed it, get it sealed, and adjust the level and see if that solves it.
Thanks!
Ken

 

Actually, I was wondering if the relief hole could be worn and allowing too much fluid back too quickly. I don't really understand exactly how that bit works.
Thanks
Ken

 

the relief hole is just that!
it allows fluid to return back to the reservoir, AFTER the brake lever has been released, and the caliper pistons push back in,
if the relief hole was worn, it still shouldn't pressurise the reservoir,
I'm inclined to think its just overfilled.
stu

 

look at the diagram on this page
http://www.caferacer.net/forum/vintage-motorcycle-racing/22923-rd350-front-pad-thickness.html
if the piston were farther to the right, it would pressurize the reservoir then the lines. are you sure the rebuild kit had the right parts ?

 

Compressed air doesn't move like compressed brake fluid. You must remove as much air from the line and caliper as possible. I use the over night gravity pull method to get fluid through the line. Then i re-connect the line and bleed the caliper. After 100 miles or so inspect everything and bleed again. Hope this helps.

Gary H.

 

I just rebuilt my calipers, master cylinder and replaced the brake lines. I took a large syringe--like you can get at Tractor Supply or a farm feed and seed--attached a 1/4 inch tube to the tip, pumped fluid in through the bleeder valve until fluid reached the master cylinder, did the same thing to the other caliper and then bled the brakes in the normal manner. I was finished in less than 30 minutes. On a rebuild I think reverse bleeding is the best and quickest method. Or--perhaps I was just lucky.

 

I don't have anything to offer but wow, that reverse method is great.

Good luck!

 

this sounds a good way to bleed air out, but is there a danger of introducing more air when the syringe is filled?
stu

 

"this sounds a good way to bleed air out, but is there a danger of introducing more air when the syringe is filled?"


With a 60 ml syringe I didn't have to refill during the bleeding of the caliper, and I refilled after completing the first one. That said, it is almost impossible to hook up the tube without getting some air in it. But simply holding the syringe above the caliper allowed the air bubble to float up the tubing into the syringe.

 

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With a 60 ml syringe I didn't have to refill during the bleeding of the caliper
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ah! I see, that's a big syringe!!
stu

 

Yep, it's not for the flu shot, thank heavens! I got mine on ebay, but I think they can be found at places like Tractor Supply or farm feed and seed stores. The one I used was not made for needles, but for squirting medication in the mouth of animal. 1/4 tubing fits nicely on the tip. It is referred to as a catheter tip--ouch! Here's what mine looks like. I only bought one or two so it was about 2-3 dollars.

http://www.exmed.net/p-1817-covidie...jf29EpmSSKJuHOdsnoGAmwABRjkurTQdwLBoCefTw_wcB