Topic

What is the difference between the white and black PRT's. I have a manual vvc that has had it's head gasket done by a previous owner that is fitted with a white one.

The situation is complicated because three or four colours - white, cream, grey and black should denote different opening temperatures, the complication being that sometimes the colour doesn't denote the temperature.

The grey one opens at 82 deg C, the black and cream ones open at 88 deg c. The other difference is the "pressure" at which they open as well as temperature. The black opens at 88 deg C,but requires a higher pressure to activate below this temp. (V8 engines) The cream and grey operate at pressures more suited to the 4 cylinder engine.
The white one appears to be interchangeable with the grey one.