.....although from what Andrew says I suggest that Renault after a while found that the Brown cap on the Turbo...due to higher engine temperature...was releasing the pressure too soon, so they fitted a slightly higher rating pressure cap ...the Blue one...in their later models...... thats assuming the Blue one is the higher rating, which to me makes sense. I just cannot see why they would fit a lower pressure cap to an engine that gets hotter, and therefore requires a higher pressure cap, noting that the higher the pressure, the higher the boiling point will be.
