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Nipple letting air in


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When i bleed my brakes and undo the bleed nipples, one of them looks like you are getting air out when in fact it must be entering around the nipple threads and then coming out through the bleed tube.

I am opening all my bleed nipples by the same amount it is just the one which seems different.

They are Caterham std brake calipers.

I have read a number of previous threads on blatchat and some people seem to have used ptfe tape on the nipple thread, is this an accepted solution ?

Any alternatives or words of advice welcome ? Would a new nipple make a difference ?

Thanks for any replies.

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I have finished bleeding them now so will take the car for a test drive in the next couple of days and see how i get on.

The nipples aren't leaking when shut, so that is not a problem.

I have new fluid.

The question is when you open the nipple whilst bleeding the brakes it seems like air is being drawn through the nipple as described in the previous thread. So it seems like there is lots of air coming out of the brake lines whereas in reality i think air is just being drawn in around the open nipple by the pressure of brake fluid coming out of the end of the nipple into the drain tube.

I will see how i get on.

Thanks for your replies.


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As has been said if you are using a pressure bleeder such as Esibleed there is absolutely no possibility that air is being drawn into the system via the threads.

As has been suggested the nipple seals at the bottom of via its conical shape.

Have a look at this picture of a BLEED NIPPLE

The drilling to allow fluid to bleed from the calliper is in the centre of the tapping at the "bottom of the hole whereas the escape point for the nipple is on the side.


If you are getting fluid seeping from the threads during bleeding I will guarantee that the nipple is blocked.

With nothing connected to the M/C remove the nipple completely and with a fine drill bit clean out the centre of the nipple and the hole on the side. and blow through with an airline or a bike tyre pump. Not your mouth as BF is poisonous.

Be prepared for fluid loss. Put the nipple back in re attach the Esibleed and bleed the system again.



Edited by - oldbutnotslow on 18 Jun 2014 15:06:50

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