Master cylinder not pumping?

**nathanwhite** · 4th March 2013, 16:22

I've been making (small) steps recently to get my bucket up and running.

I have discovered recently that my master cylinder is not pumping liquid. At all.
So it's on the bench, recently reassebled, gonna test it out, just to make sure I haven't broken anything. Fill the resoviour up with water (yes, I know water /= brake fluid. Brake fluid is hydroscopc etc) stick my finger over the outlet hole and start pumping the lever.

Nothing.

I do feel some suction on my finger, but that is about all that happens. Both orfices from the piston bore to the resoviour have been checked and are clear, yet still nothing comes down.

I'm stumped, any ideas?

**bogan** · 4th March 2013, 16:43

So just not pumping liquid, or not getting pressure as well? Like, if you put a bolt instead of the banjo, will the lever go firm?

**nathanwhite** · 4th March 2013, 16:53

Lever doesn't go firm with a bolt in.

So, air leak?

**Katman** · 4th March 2013, 17:26

As you pump the lever in you need to release the pressure of your finger over the hole so air is allowed to escape.

Before letting the lever back out block the hole off completely to stop air getting back in.

Repeat the process until brake fluid squirts out instead of air.

Once the master cylinder is 'bled' you can take your finger off and screw in the banjo bolt.

**nathanwhite** · 4th March 2013, 17:50

Originally Posted by Katman

As you pump the lever in you need to release the pressure of your finger over the hole so air is allowed to escape.

Before letting the lever back out block the hole off completely to stop air getting back in.

Repeat the process until brake fluid squirts out instead of air.

Once the master cylinder is 'bled' you can take your finger off and screw in the banjo bolt.

Alrighty, I tried that. Still nothing.

**bogan** · 4th March 2013, 18:07

If you're not getting pressure with what should be a hydraulocked (sp) system, the only thing it can be is a leak, what is the seal and bore condition?

**koba** · 4th March 2013, 18:16

You knew yet you still...

Pour water (might as well now you have started) into where the banjo bold goes, make sure everything is as full as you can with fluid and try again.
If it still doesn't work replace the master cylinder or the seals. If you do replace the seals make sure the bore is in good nick.

I'm quite rough with a lot of things but I'm not comfortable with the idea of water inside brake hydraulics. I recommend cleaning that shit out as much as possible!

**nathanwhite** · 4th March 2013, 19:26

Originally Posted by koba

You knew yet you still...

Pour water (might as well now you have started) into where the banjo bold goes, make sure everything is as full as you can with fluid and try again.
If it still doesn't work replace the master cylinder or the seals. If you do replace the seals make sure the bore is in good nick.

I'm quite rough with a lot of things but I'm not comfortable with the idea of water inside brake hydraulics. I recommend cleaning that shit out as much as possible!

Yeah, will be checking everything over again tomorrow.

Water is easier to get rid of. Also I'm lazy and don't wear gloves and brake fluid is naaasty stuff.