Brake bleeding issues

Right, I've got myself a Motrax Big brake bleeder. It's a vaccum pump with a variety of hoses and what not.

Had it for a while and used it before to renew brake fluid... simples. The other day I used it to completely drain all brake fluid from the front. I did this because my original goal was to replace the hoses for new braided hoses. Just after doing this though I decided to go for a whole new USD front end from a gsxr.

So today I wanted to refill the and bleed the front brake system.

-I filled up my front reservoir and used the vacuum pump on the bleed nipples of each calliper individually to draw the new fluid through the brake system.

-I only undid the bleed nipples by half a turn as stated in the haynes manual

-I made perfectly sure the reservoir didn't fall below the lower line.

-However, after nearly a litre of brake fluid there were still constant air bubbles emerging from the bleed nipples.

Is this to be expected or have made a bit of cluster f***?

try bleeding them the old fashioned way and see if there's any difference.

h.

[Sid Squid]

Do it the manual way, (ie the way that works), by pushing the fluid through the system rather than dragging it, and air through the threads of the bleed nipples - which is what your problem very likely is.

If you must use the vacuum thing, try sealing the nipples with PTFE or perhaps some heavy grease on the threads.

That was my thinking as well, obviously after I had run out of brake fluid. I'll have a go tomorrow.

Cheers Guys

[yorkie_chris]

And stop buying crap from motrax while you're about it.

Is the lever firm?


When doing any bleeding, if it doesn't work after a couple of tries then you have some problem, like missing a bleed point somewhere. It does make me cringe when people say "it still feels the same after 14 gallons of brake fluid!!!!!1!!"

[fastdruid]

I've had very good results by once I've got enough fluid into the system just pumping the pistons out and then pressing them back in, prevents any chance of air entering the system and moves enough fluid in each squrt to move most air pockets.

Also uses a fraction of the fluid.

Druid

Hey yorkie. Are you the same yorkie guard commander from the guard room a Waterbeach with the SV?

[yorkie_chris]

Originally Posted by Chris Bird

Hey yorkie. Are you the same yorkie guard commander from the guard room a Waterbeach with the SV?

Nope, I'm from Halifax and not in that job

A little tip that might be useful to peeps
After bleeding satisfactorily leave the bike overnight with a cable tie holding pressure on the brake system,this would normally expunge any tiny amounts of air still in the system to an area where it can be easily bled

[embee]

I use the Mityvac, same principle as the Motrax one.

The thing is you don't need to worry about the bubbles at the bleed nipple, as said it is simply air getting in past the threads, but it can't get into the brake system because of the pressure differences, the pressure in the clear bleed pipe to the vac pump is lower than the pressure in the brake system so the flow can only be out of the brake system.

Just pump it until enough fluid has come through to purge the brake system, then nip up the nipple while it is still under some vacuum. That's it.