As mentioned before, HGF failures are attributable to an unfavourable temperature gradient either side of the thermostat, this is due in the most part to overcooling via the long radiator run.

This is not a new phenomenon but has been experienced in just about every mid-engined car.

There are three possible modifications that one can make:

1. Install a remote thermostat
2. Drill the thermostat ring to allow coolant flow, even through a closed thermostat
3. Install a temperature and pressure sensitive thermostat.

1. The remote thermostat

The remote thermostat solution was first implemented in the 1980s on the Ford RS200 rally car, which had a mid-mounted Cosworth BDT turbo producing upward of 400BHP. The cycling effect in the cooling system destroyed a few engines before Hart moved the thermostat to a remote location. This has been common practice on many mid-engined cars since.

For Carl's remote thermostat solution, click here.

2. The drilled thermostat

This solution was highlighted by friends and competitors in the MGCC MGF Cup series. Because of the remote nature of the radiator causing larger than 'normal' [compared to FWD applications] changes in coolant temperature entering the engine causing thermal cycling. This phenomena was found to be significantly damped by drilling small holes in the thermostat ring.

Drilling the thermostat does lessen the cycling problem to an extent (and is data available, captured from thermo-couples in the cooling system, to show its effectiveness). It is not a complete solution however.

For Dieter's drilled thermostat directions, click here.

3. Temperature and pressure sensitive thermostat

Not much information available on this innovation, but this new type of thermostat is currently being fitted to Landrover Freelanders. By extrapolation, one might reasonably expect them to find their way onto MG and Rover models in due course...