SUPER pressurised coolant system! No no no

[rjdevinett]

Hi again.
I'm sure I only come on here with my problems, but here goes.
My coolant system/tank looks low and the low level warning comes on the dash. But when I release the cap, the pressure releases and tank goes back to a normal level. But when it looks low, you can the feel the coolant pipes etc, and they seem fit to burst with the pressure. You can even here it popping back to normal size when I release the cap. Scares me!
Do you have any ideas or have had similar problems please.
Thank you.

P.S. I'm going to add some things to, what did you do today.....etc. haha.