Bleed nipple problems

davetherave · Unread post by **davetherave** » 07 Aug 2009, 14:07

I have just removed the hydraflush that i put in and replaced with LHM, but cant get the bleed nipple undone at the rear brakes, it just shears, anyone come across this or got any ideas?
Cheers

Unread post by **Paul-R** » 07 Aug 2009, 14:23

If you've sheared the nipple off then your options are limited. You may have to take the caliper (or cylinder - what car are we talking about?) and send it a machine shop for drilling out and thread chasing. This might cost more than a replacement one so get prices first - especially for a s/h item if you don't mind using one.

You may be able to get the remains out by hammering an Allen key into the central hole of the nipple. Don't try unscrewing immediately but try giving it a little tweak to tighten it up before unscrewing. The idea of this is to break any rust seal round off the internal hole in the "closing" direction so that you can apply full force in the unscrewing direction.

There are commercial broken bolt/stud extractors available that work on this principle.

steelcityuk · Unread post by **steelcityuk** » 07 Aug 2009, 15:46

Any chance you could MIG on a bolt, this could work well because the heat could help break the corrosion 'seal' but to be safe I would want the caliper on the bench and drained as well as possible. The rear calipers tend to 'weld' themselves to the rear arms too due to corrosion.

Let us know how you get on.

Steve.

Unread post by **CitroJim** » 07 Aug 2009, 16:02

This used to be a big problem on 205GTi alloy front calipers and not helped by that horrible brake fluid stuff they use.

I used to drill the remains of the old nipple out and tap it the next size up. M6 to M8. This often upset the seating of the nipple and off-times the seal would be poor.

In that case, I'd turn up a brass adaptor to take the original size nipple.

Like this:

I apologise for the picture quality.

Xantidote · Unread post by **Xantidote** » 07 Aug 2009, 18:51

When you say it just shears, do you mean the exposed part of the nipple has sheared off, or is the nipple turning in the caliper, suggested it's stripped the thread in the caliper? If the latter, then as Jim says, you could have it drilled out and tapped to a larger diameter, or (my preference) find another caliper.

When I decide to flush/change the LHM on my car, maybe I should check all the nipples function correctly, before anything else.

Martin

steelcityuk · Unread post by **steelcityuk** » 07 Aug 2009, 19:04

I usually finish any work off on the hydraulics with a smear of grease/coppaslip around the threads to try and stop moisture ingess.

Nice work that Jim.

Steve.

Xantidote · Unread post by **Xantidote** » 07 Aug 2009, 19:49

I also do the same as Steve, applying copaslip around the nipple's thread where it disappears into the caliper

Good luck - Martin

davetherave · Unread post by **davetherave** » 07 Aug 2009, 20:14

Thanks! all good sugestions!
It is just the nut that has sheared not the thread.
Im off to spain tomorrow

(in the xantia!) so xill have another crack when i get back to blighty! Perhaps ill try molegrips and a bit of a wd40 soaking and hope i can get them off and replace with new/ second hand ones!

uncle buck · Unread post by **uncle buck** » 07 Aug 2009, 23:21

A good tip when tackling bleed nipples is to use a close fitting ring spanner....holding a steady amount of pressure on the spanner to undo the nipple start tapping the end of the nipple with a small hammer keep tapping it as you hold the pressure on the spanner....most of the time this will crack the nipple free.
Make sure you tap the nipple square on or you may snap it off!

A dose of Plus gas penetrating fluid before you try this will help.

As recomended by others if you apply copper slip to the threads of the nipple it should loosen easy in the future.

Cheers.

Unread post by **Old-Guy** » 08 Aug 2009, 10:01

Personally I use Wynn's PTFE-based 'white grease' rather than copperslip on brake nipples. My thinking is that as the callipers don't get very hot and white grease is intended to lubricate and protect exposed mechanisms it ought to be better than copper-slip which is intended for high-temp use.

I also use white grease liberally on the mechanical bits of the height control system.

Guy