Header tank water level

[Giles]

I have fitted a new header tank - one of Vmad's ones (very nice). Was just thinking about the water level. I filled it up well and have allowed it to then find its level by blowing a bit out of the overflow on the basis that it will then be full when hot. The idea being to have the max amout of water above the pump.

I was then thinking about this (always a bad move!). The old expansion bottle was only 1/3 full and the rest was air. Air will compress but water will not. The water will expand a certain amout when it gets up to running temp so will compress this air up to the 20psi of the cap before it lets any out. With the old system it may well have never got to 20psi. With only a small amout of air in the new system I am thinking it will be running a lot closer to or at about the 20psi all the time it is at full running temp. So putting more strain on hoses and gaskets.

So options -

1. This is not the case and I need to stop thinking about things !!
2. Put less water in the header tank - partly defeats the object of having it but I suppose will fill up when gets hot so perhaps not but how much of a air pocket do I leave, how do I know I have plenty of water?
3. Run a lower pressure cap. Lower boiling point,( localised boiling etc ???)

I like the sound of 1!!

any thoughts?

[Jeff]

Ask Chris (V Mad)

[V Mad]

Option 2 is ok if you want to, but the low level buzzer will soon drive you nuts.
Dont run a lower pressure cap, otherwise you might boil up on a hot day in the summer.
I would choose option 1; enjoy! Thats the whole point of fitting a proper header tank.

[Giles]

thanks Chris - said I should not think about things!! - nice bit of kit by the way