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[PeteT]

Hi, after spending more time than is really healthy investigating how to remove a stubborn bleed nipple I found a method that worked [for me anyway].
First job is to find a metal insert for the centre of the bleed screw that will fit inside all the way to the bottom ( a drill bit is ideal). Job two is the liberal application of WD40 to the thread of the nipple and while that starts to work its magic use a blow torch to heat the metal shank (drill bit). Once the tip is hot  insert it into the bleed nipple - this introduces a high heat source deep within the item rather than superficially heating the outside of the caliper. Leave the shank in place for a minute and with it still in place attempt to turn the nipple - I don't have to tell you to be gentle do I ?

Once loose remove the drill shank / wire / whatever you used.

As I say it worked for me on all the screws I tried it on. Please let me know if you use it and what level of success you have.

Cheers

[jonnyboyws6]

Intresting idea, but how can you objectively say it works? How can you say for sure that the nipple wouldn't have come out without doing this?

I don't mean this to sound arguementative, just a discussion.

In my opinion, the only way you can get enough heat to free off any seized fastener is with oxy-acetylene, a blow torch (butane?) doesn't get hot enough, especially not if you are relying on the heat to transfer from the drill shank to the nipple. But then my ideas are just opinions too, maybe you are introducing enough heat and my torch is a "lump hammer to crack a wallnut" style overkill! If it works for you, keep doing it.

[Webby the Bear]

Intresting idea, but how can you objectively say it works? How can you say for sure that the nipple wouldn't have come out without doing this?

I don't mean this to sound arguementative, just a discussion.

In my opinion, the only way you can get enough heat to free off any seized fastener is with oxy-acetylene, a blow torch (butane?) doesn't get hot enough, especially not if you are relying on the heat to transfer from the drill shank to the nipple. But then my ideas are just opinions too, maybe you are introducing enough heat and my torch is a "lump hammer to crack a wallnut" style overkill! If it works for you, keep doing it.

He did mention it worked for him and for others to try to see what results they got

[jonnyboyws6]

Yes, I didn't mean it to sound contradictory or arguementative, sorry if it came across that way.

[PeteT]

As with all ideas the proof comes from experimentation. Having freed the screws on my car will I ever have to do it again? With previous vehicles I've planned to carry out the simple task of bleeding brakes to put the ring spanner in place and then, well you know the feeling, do you feel lucky? Well do you? This was the if it doesn't move when I think it should -do something before I break it approach.
Oxy acetylene will certainly apply a lot of heat but with quite a few risks. Even a standard blow torch pointed in the wrong direction is going to cost.
I actually think applying extreme cold to the centre of the bleed screw would be better and "shrink" the screw, it would also make it very brittle. If I get  another chance and some liquid nitrogen I may give it a try....

[jonnyboyws6]

My mate the tool rep keeps promising me a sampler aerosol of a freezing spray which is supposed to shrink stuff to free it. Hasn't turned up yet but if it ever does I will report back.

My general plan of attack with bleed nipples is wire brush, penetrating oil, then bang the caliper with a hammer a few times as near as possible to the nipple, and keep my fingers crossed! French stuff is the worst, they often have ally calipers/cylinders with tiny diameter bleed nipples which once the corrosion starts (dissimilar metals) you haven't got a hope in hell with. I have had much more success (luck?) with Vauxhalls.

[Webby the Bear]

My practise car has been sat for ages. bleed nipples undid with no fuss.

i'd personally, like you, go down the penetrating oil route first. then wire wool. then if still not budging sell the car and get a new one