seized bleed nipple

[tanto]

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hello
I am having trouble with the bleed nipple for both rear callipers for my car they are seized solid I have tried heat and a freeze spray but the just refuse to budge I cant think what else to try
I currently have them in shed replacing the seals

 

[Battoussai]

Bang them!

Hit SLIGHTY with a hammer various times (like 50) like an earthquake.
This might crack the rust inside the bolt. Then spray with WD40 or similar and hammer again just to help the fluid get in between the cracks.
Wait a couple hours and then try to undo the bolt.

And heat should expand metal so by doing this you are tightenning the bolt even more.

 

[verbal_kint]

They can be right pigs. I would get new ones in as I bet your ones will be in a state by the time you get them out.

I always use a true penetrating fluid like Plus gas, WD doesn't have enough creep ability. If you have an impact drill use that, but get one with a low max torque that will give enough shock to the rust.

 

[verbal_kint]

Bang them!
And heat should expand metal so by doing this you are tightenning the bolt even more.

That is true but metals have different thermal reactions, so from ancient memory cast steel expands less than stainless.

But the heat/freeze approach is to break the rust connection by the expansion and contraction of the metals.