E30 Zone

On my m40, I have noticed that the top coolant hose is sometimes real hard when squeezed. I mean like it's under slot of pressure.

When I take the rad cap off the coolant pipe becomes squeezy again.

The car had been driven a few miles home and was properly warmed up.

Is this normal and if not, what's wrong?

Should imagine it is normal, the system will get under a bit of pressure due to the heat and steam involved, whence why it advises you do not take the rad cap off when the engine is hot.