Brake Bleed Nipples "weeping"

[topperuk]

Hi all,

Sorry for what might be a stupid question..

I've overhauled both front calipers today on my bike (tokico 2 pots)..

Have bled and all happy - but have just used a new (to me) trick of cable tieing the brake lever back to the bar to get the last of any air out of the system.

It's been sitting for around 4 hours now and i'm noticing slight weeping of brake fluid from the (new TRK) bleed nipples of both front calipers..

Is this normal?

They're under extreme pressure - like lever pulled solid back against the bars..

I've never ever noticed this before - but i've never left a brake system under full pressure for such a sustained period of time..

The fluid is weeping from the threads around the edge - not from the centre holes..

It really is minor - after 4 hours you'd be lucky to get anywhere near a drop, but it is there..

Cheers!!

[jeffyjeff]

Hi topperuk.
Those calipers were not designed for a full on lever-to-the-bars brake application for an extended interval like that. If very slight seepage past the bleed nipple threads is less than a drop in 4 hours, I wouldn't worry about it. I do not know who invented the cable tie trick, but I doubt is was anyone from Tokico, Nissin, Brembo, or any of the brake component manufacturers. The brake system is not designed to purge air that way.

If the weepage bothers you, apply some thread sealant (not Teflon tape) to the bleed nipples, and bleed again.
____________________
History shows again and again how nature points out the folly of men - BOC

[redeem ouzzer]

My GSXR1100 has had 48 hours of the cable tie treatment over the last week and didn’t pass a single molecule of fluid out of any single joint. It’s not ok for the bleed nipples to pass any fluid whatsoever. Bin the after market nipples and fit genuine.
____________________
Be a REAL MAN!

[Bhud]

The bleed hole (caliper side) on a brake caliper is fairly easy to damage by overtightening the bleed nipple. Hope that isn't what's happened.

[Riejufixing]

[A100man]

[A100man]

FWIW I don't the think the requirement is to pull the lever back using full pressure. you only need to open the passages to allow ar bubbles to float up. A modest but sustained pull-back usually satisfies.
____________________
Now: A100, GT250A, XJ598, FZ750

Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600

[Nobby the Bastard]

Any seepage is bad. Did you get the right nipples? The have slightly different champhering.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[sickpup]

[jeffyjeff]

After hearing the voices of reason (thank you Forced and sickpup), I stand corrected.
But I still question why anyone would cable tie the brake lever in order to "get any last air" out of the system. Once the master cylinder piston seal covers the compensating port, all path of air escape is effectively blocked. How is pressurizing the brake line going to help air float up to the top---magic? If you can pull your brake lever all the way to the handlebar, something is wrong. Either there is still air in the system, you have a leaking seal, or you have bent the brake lever.
Correct me if I'm wrong, but I have bled hundreds of brakes successfully, (including the VFR linked brakes and the BMW servo assist) without resorting to a cable tie on the brake lever.
____________________
History shows again and again how nature points out the folly of men - BOC

[sickpup]

[topperuk]

The brakes are bled and are solid (well as solid as they get on a kawasaki 650!)

I was told that applying pressure after a major overhaul serves 2 purposes.. 1. A system leak check - leave it overnight and see if you have any leaks. 2. The pressure applied can help any of the tiny microbubbles left behind to work their way out (whether this works or not I don't know, but it's mainly the leak check I'm using it for..)

Back to the original issue - the weeping past the threads (not through the central hole).. I've dug the original nipples out of the bin and they had put a wrap of PTFE around the threads - gonna give this a bash..

[Kris]

[sickpup]

[Riejufixing]

[Kris]

[Riejufixing]

[Riejufixing]

[sickpup]

[topperuk]

Thanks all for your input on this thread.

It's obviously bothered me overnight - I was worried I'd have stripped the threads in the calipers even though I was sure I hadn't overtightened them! - so I took the new bleed nipples out this morning to compare them to the oem ones.

As you can see the tapered end is completely different, no wonder it didn't seal properly..

Complaint email sent to wemoto!

Thanks all - i'll get some of some new OEM ones (the other ones came as part of the caliper servicing kit for my bike from TRK via wemoto) and swap the older OEM ones over when they arrive..

Cheers,

Dan

[Riejufixing]

Nice pic. Shows the difference and also exactly why PTFE on the threadis is useless for sealing (the fluid would go straight up the inside of the nipple anyway).

[kolu]

[sickpup]

[Nobby the Bastard]

It's nice to be right two days I a row.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[weasley]