Pressure Relief Remote Thermostat
A Pressure Relief Remote Thermostat (PRRT), or sometimes just PRT, is used to increase the amount of coolant flowing around the engine. The PRRT has a bypass valve opening when the coolant pump is flowing too much coolant for the radiator circuit. This valve is reducing pressure difference inside the whole circuit, achieving at the same time a more constant temperature inside the engine.
PRRT Colours
- Cream is 87° With Medium Spring
- Black is 82° With Hard Spring (Not suitable for Rover K engines)
- Grey is 82° With Light Spring
Land Rover Part number for cream stat (including all the hoses and clips needed to make it fit) is PCH001190
Land Rover Part number for grey stat (full hoses kit, similar to PCH001190 but with a non useable plastic elbow with small takeoff) is PEL500150
MG part number for PRRT kit is PCH003320. This kit is for the MGF wich cooling system is very close to the Elise's so it should require less modifications than the Land Rover kit. It comes with cream (87°C) stat.
Land Rover part number for grey stat (standalone) is PEL500110
Rover part number for both Black and Cream stat (standalone) is PEM101020 - the fact two different thermostats share the same part number could cause some confusion.
The downside with the cream PRRT is that the stat won't open below 1500-1750 rpm due to the sping rate.
For DIY instructions on fitting please see the how to fit a PRRT guide.