Cap Wobble- Just A Check

[lfowers]

Hi,
I bought a brand new expansion tank and cap from Audi main dealer for £31. Now unfortunately i've not been able to bleed the system yet because of a leak on the quick coupling joint off the head. I've ordered one of these today and it will come on Friday from the main dealer.

My question - I've fitted the new expansion tank and just gone to screw the cap on and it screws on and locks with a click. Once it has clicked you cannot screw it any further and i'm just worried whether it will hold pressure because it still wobbles in the hole.

tldr; Cap wobbles in expansion tank despite locking with a click. Is this normal?

Thanks

 

[SmithyAG]

Mine definitely doesn't wobble once its clicked, it's tight and snug.

 

[Orange225]

Is it like a pressure safety device to stop you undoing it when there's pressure in it.

 

[lfowers]

Thanks for the replies. I know the click is supposed to be there its just the fact it has play in it once its locked in. Have Audi given me the wrong cap/tank combo and resulting in it not holding pressure?

 

[lfowers]

Ive just had another look at the cap and it appears the black plastic bit moves around in the blue clips when you hold the cap in your hand. It appears that the blue bit that actually screws into the tank doesn't screw tight in the threads because of the locking thing and the cap can never pull on the threads which if it did would cause no wobbling.
I apologise if this doesn't make sense and sounds like its coming from my behind

 

[lfowers]

Well after bleeding the system and going for a drive with the cap locked in, it turns out that it does hold the pressure and the bubbling coolant has stopped!

 

[SmithyAG]

Sounds like a result to me!