Do I need a new expansion tank?

[Griffo46]

Car - 2007 3.0si
So yesterday I checked the coolant level and the float was well below level. I topped it up and completed the bleed process. Float still remained at the bottom and the stick was definitely there.
Today, I checked level again and the stick has vanished, float there and coolant visible.
Shall I just consider getting a new tank and sensor?

 

[JamesClements]

Its a fairly easy replacement - although when mine split it was spraying out the back of the tank after less than a mile and all over the engine - have you tried removing the plastic cover thingy (technical term ) on the radiator and checked for any staining/residue with a torch?

 

[colb]

Since you topped it up and its gone down since it must be leaking away somewhere, odds on the tank has a split that opens up when hot so probably best to put a new one in. As to the indicator stick not moving is that the case when you top it up it stays at the bottom?
Maybe the float is punctured and filled with coolant and causing it to stay at the bottom instead of floating. Best all round to replace the tank.

 

[Griffo46]

I haven’t experienced any leaking yet, unless the amount is so small I can’t tell. I’m more worried about where the stick is, it’s not attached to the float in the ‘after’ photo. I think I’ll get a price on a new tank and consider a full flush too. Thanks for peoples feedback