Rear brake letting air in

Northern Monkey · Jul 29, 2012

I broke my nipple off the rear brake ad replaced it with a stainless big bolt thing with stainless nipple inside it .

I can't say it didnt do iit before otherwise I wouldn't have been messing with the nipple in the first place to break it!

Basically after 2-3 months the rear pedal travels fully down and offers little or no braking effort until I re bleed it.

The question.......... Do I need to or should I have 'sealed' or glued in the stainless repair thing - or is it likely to be something else that's leaking air in and what/ how can I check?

Cheers it's a 2002 R1150GSA with the BMW clippers

JayC · Jul 29, 2012

If there is no 'O' ring/seal between the nipple and it's socket then I would expect it to leak personally.

Northern Monkey · Jul 29, 2012

Don't recall seeing one but it doesn't appear to be leaking either?!?

JayC · Jul 29, 2012

If your pads and disc are in good condition and pedal is increasing its travel and no beneficial braking performance is noted then it is leaking , whether it's the fluid or air. Is it leaking at all around the pistons?

Northern Monkey · Jul 29, 2012

Again not that I can see- does the master cylinder have seals that wear out?? The fluid level seems to remain constant :nenau

Roadcaptain · Jul 29, 2012

master cylinder will have seals that can leak and let fluid passed, keeping levels constant and poor braking

Northern Monkey · Jul 29, 2012

Think that could be the smoking gun so to speak...... Wonder how much I will be spanked for a new one! Thanks

littleredrooster · Jul 30, 2012

Northern Monkey said:
...a stainless big bolt thing with stainless nipple inside it...

So - is it a proper brake nipple for a BMW caliper or is it summat else? There's no 'glue' or 'O' rings in nipples, merely a tapered seat.

I'm struggling to believe that you would mess about with a primary safety system. Please tell me you're taking the mickey here...

Northern Monkey · Jul 30, 2012

littleredrooster said:
I'm struggling to believe that you would mess about with a primary safety system. Please tell me you're taking the mickey here...

messing around / repairing - the parts are from motorworks as a common repair for shit/siezed bleed nipples provided by bmw.

forgive me i thought not having any rear brake efficiency was worthy of particular note and attention!

when i bleed them they work fine - there is an issue somewhere where air is getting in - hence the question.

here s the part from motorworks

Stainless steel brake caliper bleed nipple holder - 2 piston sliding rear caliper ( R850 / R1100 / R1150 / Cruiser ) | SSA00475

This is a special stainless steel holder for the 6mm bleed screw fitted to the rear caliper. The nipple is prone to seizing and breaking off when removal is attempted. The nipple holder is NOT available from BMW.

littleredrooster · Jul 30, 2012

Right. If you'd said it was the repair kit from Motorworks, I would perhaps have known what you were on about. Bit different from "...a stainless big bolt thing with stainless nipple inside it.."

As it needs no sealant or 'O' ring, the problem (most probably) is that the seat has a foreign object in it preventing a proper seal being made. Take the nipple assembly out and clean the tapered end and check (and clean if necessary) the seat inside the caliper, making sure that there is nothing in the hole / on the seating area.

After reassembly, bleed the brake and press and hold the pedal for at least five minutes (find a way to wedge it) to see if any weepage occurs past the nipple. If not, the problem may lie elsewhere, although sometimes air can get in easier than fluid can get out!

Northern Monkey · Jul 30, 2012

Thanks - will give that a go

Black Rooster · Jul 30, 2012

if threads are leaking you could try some PTFE tape on them that could help

http://www.ebay.co.uk/itm/2-x-P-T-F...DIY_Materials_Plumbing_MJ&hash=item35bae1b267

Dr Bones · Jul 30, 2012

I was in the same position as you a couple of months back (bleed nipple seized in carrier). I replaced mine with a stainless one. When I took the old one out it had a copper washer fitted, so I just put a new copper washer on when I fitted the new one. I've had no problems for last few thousand miles.

(Just to be clear the copper washer goes on the carrier, not the brake nipple)

littleredrooster · Jul 30, 2012

Black Rooster said:
if threads are leaking you could try some PTFE tape on them that could help

http://www.ebay.co.uk/itm/2-x-P-T-F...DIY_Materials_Plumbing_MJ&hash=item35bae1b267

...one of the worst things you can do is put PTFE tape on a brake union of any sort. Unless you want sudden, unannounced brake failure. No part of a brake system seals on the threads; that crudity is reserved for plumbers.

Black Rooster · Jul 30, 2012

never knew that better take a wee note about that

when my SV came back from the suzuki dealers after a service and it looked ptfe around its bleed nipples , i had new hoses fitted but thats in the past aprrox 2006 or 07

Steptoe · Jul 30, 2012

littleredrooster said:
As it needs no sealant or 'O' ring,

There is an 'O' ring.
It's located on the brake nipple holder, it sits between the nipple holder and the caliper.

Northern monkey should have checked the old holder a bit more diligently when he removed it.

Northern Monkey · Jul 30, 2012

Steptoe said:
There is an 'O' ring.
It's located on the brake nipple holder, it sits between the nipple holder and the caliper.

Northern monkey should have checked the old holder a bit more diligently when he removed it.

If the nipple was seized into the holder would I / should I have seen the o ring? As all I did was unbolt the old one with knackered nipple and screw new one in

littleredrooster · Jul 30, 2012

Steptoe said:
There is an 'O' ring.
It's located on the brake nipple holder, it sits between the nipple holder and the caliper.

Northern monkey should have checked the old holder a bit more diligently when he removed it.

My reply of course referred to an ordinary nipple, not to the two-piece affair which subsequently turned out to be fitted. I should have spotted that too.

Steptoe · Jul 31, 2012

Northern Monkey said:
If the nipple was seized into the holder would I / should I have seen the o ring? As all I did was unbolt the old one with knackered nipple and screw new one in

You've just confirmed what i posted

Reread what i said.

The 'O' ring isn't on the nipple. It's on the nipple holder, the bit you unscrewed.
You might think there wasn't anything on it, buit if you look closely you'll see it.

Rear brake letting air in

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