Header tank coolant level - why is there a 'min' level?

[Pootle]

I've always believed the header tank should always be FULL to the brim under all circumstances, cold or hot. Excess coolant transfers to and from the burp tank.

My garage say that it's okay if there's some air above the coolant in the header tank "that's why the 'min' level is marked on there sir".

So why IS there a "min" level marked on the header tank?

[Hacksawbob]

I have never seen a min level, Is it in line with the sensors level?

[1664]

probably means the tank behind the number plate flap = 'expansion tank'?

the garage man I mean

[Pootle]

probably means the tank behind the number plate flap = 'expansion tank'?

the garage man I mean

I was pointing to the header tank... he knew which one I meant. Although maybe he thought that one WAS the expansion tank, hadn't thought of that.

[Pootle]

I have never seen a min level, Is it in line with the sensors level?

A little bit higher, the sensor tip is quite low in the tank. Click for bigger pic:

[timski]

My understanding was that the header tank should be full to the brim. At least, that's what I learnt from Simon's instructions for bleeding the system, which worked for me.

Header tank, the one INSIDE the engine bay, the one with the pressure cap, this must always be full right to the top, always, forever, period, fullstop.

from

http://www.brick-yard.co.uk/forum/bleed ... 8d.html%7C

My expansion tank is normally about half full.

My header tank has a minimum level too but I can't actually see what the level is without shining a torch through it as it's not very translucent - probably needs a clean

Tim.