Blocked Nipples!

[Descolada]

I was performing a brake clean on my wee today when I realised that the rear brake reservoir fluid was looking a little brown and in need of change.

Some time ago I did a rebuild of the front brakes and invested in a vaccuum pump. I unboxed this and attached it to the rear caliper nipple, created the vaccum and unscrewed the caliper nipple. Nothing happened so I unscrewed the nipple a little farther - still nothing (yes, I had removed the cover and rubber gasket from the brake reservoir). I gently depressed the rear brake peddle and brake fluid began to seep from the threads - but not the end of the nipple.

The brake nipple has a protective cover but I checked that nothing had made it's way down the core and then reset and tried the whole operating again. Same result. Sepage from the threads but nothing from the end of the nipple.

So the question is this. Is it possible for the brake nipple to become blocked below the threads somewhere. What's the usual course of action - replace or remove and clean?

As far as I am aware there is a simple hole in the end of the nipple (where it locates in the caliper) and not a ball type one way valve?

Thanks for any advice.

[Mr Nick]

Hi mate,

There's usually a hole on the side at the bottom of a bleed screw & they do tend to block up.

Pull it right out & poke a wire through the hole and down the core.

Like this:

[mr_diver]

First time I clean the calipers on any bike I wrap the treads on the bleed nipple in PTFE tape.

Stops them seizing into the caliper body but also stops fluid seeping through the treads when bleeding.

[Descolada]

That's a nice tip Mr Diver - thanks.

Mr Nick - I'll take it out today and have a look. Do you know if I can clamp the rubber brake pipe to stem the flow of fluid or will it crush the pipe?

[UK_Vstrom650]

If you don't remove the master cylinder cover then the fluid won't pour out - you'll just get a bit of fluid come out. I was watching a video last night on YouTube where they swapped brake nipples and were saying you should do with a full brake system. Just use a rag. Alternatively you can release brake line and turn the end upside down so gravity holds the fluid in.

[Descolada]

Wow Mr Nick - you weren't kidding about these things getting blocked. After removing the bleed nipple this is what I found;

Before:



So I gave it a good clean with a wire brush and this is what it looked like before I put it back;

After:



After completing the drain and refill of the rear brake fluid I took a "before and after" pik just to compare the difference - It put me in mind of a visit to the Scottish Motorcycle show a few years back. Mr Nick and I sat on the Ducati's on show and noticed that one of them had non functional brakes - the brake fluid in the reservoir looked worse than this  

The good stuff is in the reservoir  



That job is now complete.

But I have another question for anyone who knows anything about how the wee exhausts are constructed?

I removed the exhaust coverings to get at some rust that needed seeing to and was fascinated by what appears to be mig welds on the casing - I am trying to figure out that these are holding onto inside the can that requires mig welds?

Strange welding patterns;



.... answers on a postcard please?