air bleed screw on manifold

[alfettagtv2000]

does anybody know what the (brass) hex screw size should be for the air bleed screw on the cooling system manifold?
i think i overtightened it last time (with a metric 14 ring spanner) but now i cannot undo the hex screw with the same ring spanner as the corners are starting to round...
the hex screw has a gasket washer and a flat washer under the head...
thanks

[iachella]

It is a 14mm. Not sure what a "ring" spanner is, but guessing it's a closed end one. Try the open end of a 14mm. Or a vise-grip. If it's rounded off, you might be needing a new one, so don't worry about marring it. They are still available new. I got a couple recently.

[alfettagtv2000]

thankyou stefano...yes a ring spanner is closed all round (not sure how many points maybe 12)

[mjr]

if its starting to round, neither and open ended or ring will undo it. dress the bolt head out if you need to, then use shallow 14mm socket with a 3/8 drive ratchet, far less likeley to round it. get someone to keep some weight on the socket first and try, to stop it starting to slip. It sounds stupid, but set the ratchet to tighten first, then undo, when you have a controlled pressure on the head get someone to try tap on the ratchet head at the same time. just tap, not whack!

try that a few times, if no good try heating it and cooling it a few times?. be sure to see that the brass nut has fully cooled before you try or you will round it! dont go too hot or cool too quickly either, youre into cast aluminium. patience is the key. keep teasing it.

[alfettagtv2000]

thanks mjr...sounds like patience and perseverance is the key...
might try and use a 6 point socket to see how that goes...
is it better to try when the engine is hot or cold?

[mjr]

personally I would do it with engine cold. If you do it with engine hot, you wont be able to shock the nut by heating it, then cooling it reasonably quickly, since the nut will just continually heat soak.

I would use 6 point socket too, 12 points tend to wreck the nut, if you slip.

do you have access to air and a rivet gun with snap fitting?

heres my tried and tested for just about anything seized, works a treat.

Engine stone cold.

-Heat brass nut evenly for 15 seconds
-cool it by spraying it with WD40 or similar oil, a bit smokey, but water will cool it too quickly.
-take air rivet gun with snap, set to a lowish setting. 1 inch thick chunk of wood on the nut, and give the wood a few good 3 second zaps on the gun.
-heat again. cool again

Now undo. It should come off. if not repeat. seized nuts or bolts dont normally take more than 2-3 attempts using this method before they come free. Just be careful with too much heat on this one, being brass.