Thermostat bleed screw stuck solid - any ideas

[Spion]

I need to loosen the thermostat bleed screw but it is stuck sollid and rounding off. I've tried swearing at it, and have applied some WD40.

If it's stuck fast how can I get it out?

Or is there another point I can bleed the cooling system?

[Simon]

Some big grips, and don't overtighten it when done. Replace with a new one when appropriate.

[Spion]

Freezer spray and big grips did the trick

Had to toghten it down hard to stop weeping after bleeding tho

[robbo86]

Duck oil,the penetrating stuff i mean, doesnt it penetrate more than wd.

Or cant you just remove the bottom hose?