Technical but not boaty - apologies!

[Haven't-a-Clue]

I suspect I'll find an answer here, so here goes: 1980's Japanese m/cycle, alloy brake caliper and, presumably, mild steel bleed nipple, which seems to be corroded in place. Having had a go on one of the other calipers with the same problem, surprise, it sheared. I really don't want to take the chance of shearing this one, as it'll mean the bike is off the road just as the MoT is coming up. So, how can I free it off safely, 'cos the caliper really needs bleeding to get through the test. Oh help, help.
Ta everso in advance.

 

[FullCircle]

Lots of WD40 over a couple of days. Put it in a carrier bag and lob it in the freezer. Leave a day, then have a go with gentle persistent pressure.
No luck? Now put more WD40 on it and then put it in the oven, gas mark 3-4 for 1/2 hour. Let it cool and have another go.

By expanding and contracting it, you should loosen the corrosion off.

If not then take it to a bike shed and get them to lob it in their ultrasonic cleaning bath.

 

[Haven't-a-Clue]

I've tried the WD40, but not for long enough, I guess. /forums/images/graemlins/blush.gif Would a penetrating oil be better? Will give it a go though, thanks for tip. What a place this is for info, nice innit.
Cheers.

 

[30boat]

Bleed nipples are a pain on Jap bikes because they corrode.My BMW has them in stainless.I don't think you'll be able to get it out with WB40 or similar
I would take the caliper off the fork and drill the remains of the nipple out.It'll have a hole in the middle and that will guide the drill.You can then have a new one turned slightly oversize(stainless this time).Tap the hole for the new thread and that's it,problem over.The piston/s will have to come out either by means of compressed air or by pumping the master cylinder with the pads removed.

 

[Lakesailor]

Tried boiling water?
You can bleed calipers by slacking off the supply pipe, retracting the pads, locking off the pipe, and pumping up.
Hard to describe, but it does work.

 

[misterg]

In extremis, MIG weld a nail across the end of the nipple. The fierce heat will break the bond of the corrosion, and the nail will give you leverage to undo the nipple without crushing it. Drastic, but it has worked for me 2 times out of 2. You do need a new nipple, though.

Just remembered - the other thing I used to do: Take the caliper off its mountings and twiddle it until the brake hose is highest, then try and bleed by slackening the banjo bolt, AND/OR push the piston back in while the caliper is in this position to send air back to the master cylinder reservior. Repeat as necessary.

Andy (A100 / TS185 / Z400J / GPz550 / VFR750F)

 

[lw395]

Try lots of heat.
Hold the nipple in a vice, then heat caliper with blowlamp or hot air gun.
Failing that,
drill out nipple with left handed drills, will often undo the threaded item.
You can helicoil the casting if necessary, the thread doesn ot need to seal.
But previous advice re bleeding via feed hose is good, take the pads out, pump loads of fluid into caliper, push pistons back to expel air all the way to master cylinder. It works on some!
You may fnd a replacement part is less expensive than you think try DK MC's in Newcastle under lyme?
Good luck

 

[elton]

The handy thing about bleed nipples is that they have hole right down the middle so they're quite easy to drill out if you happen to snap them off. Just use an increasing size of drill bit down the hole until you're almost out to the threads, then bash the remaining thread from the outside edge with a hammer and a small, sharp screwdriver and it'll peel away from the calliper thread.
I agree re. WD40. Also, a good fitting spanner is needed, along with a sharp wrist action (rather than trying to turn it gently). A gentle tap on top with a hammer (after prolonger WD40 application) will also help).

 

[rogerdog]

[ QUOTE ]
Try lots of heat.
Hold the nipple in a vice, then heat caliper with blowlamp or hot air gun.


[/ QUOTE ]

Be very careful using this technique - you can damage the seals - as to the rest spot on.

I would try the boiling water method - have a few kettles and /or saucepans ready and then pour it over the calliper (not hot - but boiling water) and hopefully it will break the seal - a good fitting ring spanner and lots of sharp taps with a medium weight hammer


I echo the good luck - been there tried it ........ 2 / 3 success -other one - calliper from scrappy!

 

[Thistle]

Remember too that corroded threads can also often be released by first trying to tighten them slightly or by tapping them in with a light hammer.

 

[cliff]

Lots of good advise above - me I prefer the BF&I method. (Brute Force and Ignorance) - good soak in plus gas then give the nipple a good smack with a hammer as if it was a nail and you are trying to drive it into the caliper then an impact driver with a good HEX socket and another good smack trying to tighten it then reverse the driver and another good smack to loosen it. If you haven't sheared the nipple off apply some more plus gas and try again - tightening and slackening. the nipple will either loosen or you shear it off - if sheared in the drill press it goes and drill the remnants out and re-cut the threads - time is money and it is often cost effective to "go for it" rather than spend hours and hours trying to gently free something off.
---------------------

Artificial Intelligence is no match for Natural Stupidity

 

[Haven't-a-Clue]

Eee, by 'eck, thanks for all the suggestions. Re drilling it out, I can say right away that the designer of this particular caliper obviously costed the price of the caliper alloy by the gram! 'cos there really isn't enough metal around the nipple to risk it again (don't ask how I know!). I will try the heat and penetrating oil trick, bleeding via the hose is how I got it to work at all after replacing the seals! Flippin' cheapskate designers, oh and just to make the job a real peach, it's Honda's inbload ventirated disc blake, with the caliper gripping the disc from the INSIDE (disc mounted radially ie outside edge, if you follow). Sure makes getting it off a pain, mind you, no-one in their right minds would try stealing it! Oh well, here we go, wish me luck! /forums/images/graemlins/frown.gif

 

[mandlmaunder]

If all else fails and it goes tits up DOA in north London probably have aworking replacement waiting to be posted overnight. Great shop and the guys know their stuff.