Bleeding brakes II......

After bleeding the rear brake so easily (after being told how to do it!) I was pretty damn confident that the front brake wouldn't pose a problem at all...

So, the problem this time is brake fluid is leaking out around the base of the bleed-nipple rather than the end of it when I loosen it off and, I think, air is getting into the system at the same time and the stupid thing won't bleed...

A bit of reading on the web seems to point at the bleed nipple either needing some sort of sealant applied or the thread being damaged or the caliper being damaged somehow.  It only leaks when I loosen it, so is it knackered or am I doing it wrong (again)?

Any thoughts would be much appreciated...

Thanks for your continued help/patience...

That's a bit wierd, are you just cracking the bleed nipple open? Also does it make a good seal when you tighten it up?

Yes to both...and the bleeding it I'm using makes a good seal on the nipple, so it's not fluid leaking from there, it's definitely coming up the thread

That's a bit odd. Is it possible the shaft of the nipple has got blocked causing the fluid to be forced around it instead?

That's a thought worth exploring - if I take the nipple out altogether, is it easy enough to put back in?

Shouldn't be any more difficult than screwing in a standard bolt.

It'll give you a chance to check the state of the threads too.

Worth a look. Does seem odd behaviour.

Remember that DOT fluid acts as paint thinner... keep things clean and away from DOT liquid ; covering parts at risk with rags is a good idea.

Also, remember bleed bolts are not to be overly tightened. No idea about the torque values, but it really doesn't take much to close it. Overtightening can damage threads.

Lastly - remember to explore bike parts websites to check the diagrams of the caliper ; sometimes that can help to make sure everything is in "normal" working order!

For info: Over-tightening your bleed nipple really isn't a good idea, not just because it might snap - it's actually worse if it doesn't - the end of the nipple is a cone shape which seats into a suitable cone shaped seat at the bottom of the hole, if you over-tighten it this seat will be damaged and you will only then have the tighten it more next time.... eventually you will need a new caliper or to get the seat ground, which (I guess) won't be easy and will cost money.

Anyway, I'd guess that the thread is knackered or your bleed nipple is blocked, which I think you'd realised already.

<bodge>

try and wrap a bit of PTFE tape around your bleed nipple

</bodge>

Don't really know what PTFE tape does when it comes into contact with brake fluid, but you could find out Might just seal it for long enough to get it coming out of the nipple properly and the brakes bled. Might not also....

Take the nipple out and give it a good clean out, check that you can blow air through it before trying any bodging.

Thanks for your help - I took the bleed-nipple out and there was a bit of surface rust around the head, so I gave it a gentle clean with a wire brush, put it back in and started the bleeding orocess all over again.

This time, the air bled out as expected and the brakes are working fine - hooray!  I think I bled most of the air out of the banjo-bolt at the reservoir end, the same way I did the rear brake, so that's certainly a method worth knowing about

Now it's on charge and tomorrow will be getting the coolant level right...

Thanks for your help!