Getting everything together to start the conversion. I'm placing the thermostat valve at the top (entry) of the radiator, currently as many owners of the 2.5 & 3.0 know - the valve is at the bottom left (exit) of the radiator. All the pipes look way too big but they will be trimmed quite some way. The important thing is all the internal diameters are right. Just got to order a 90° pipe @ 38mm and several pipe clips. Easy really.

Is the conversion a common thing among S type owners? Presumably to make the system easier to bleed?

Are the details posted somewhere?

Sorry am new to the world of S types and haven't found an obvious answer with some googling!

Ha Ha, no what problem petrol S & X types have (excluding V8 & diesel) is overheating. It makes itself known by a water 'leak' due to over pressure, pinking on acceleration and general god awful running. The thermostat is placed 'after' the radiator and since that is rated at 87°C, the coolant post radiator is not hot enough to open it. Result no water flow, overheating cylinder heads, blown head gasket, etc. I've built up a few race engines and every time we find the thermostat post radiator it gets changed because it runs the engine too hot. No difference here so I've got a few more parts to arrive but it will all make sense once I've got this fitted. Jaguar have got a sprung blow-off valve on the thermostat housing and if the engine over revs while cold it will open and divert the excess pressure thru the radiator. Fingers crossed it will all go together nicely. Good luck finding anything about it on the net.

Getting there. This pipe 'deletes' the thermostat from the lower position. I was worried about this one tbh since the radiator pipe is secured by a metal band, but a quick grind and off it came. The tubing is wire-wound since it has a fair curve from the rad to the pump.

There it is. All put together - will have some figures on warm-up time and running temperature after the coolant is in, etc. Thermostat is rated at 87°c will have an OBD2 reading for that.

After a few drives I can say it takes a while to warm up, blanked off 1/² the radiator even so, about 10 minutes or so given 8°c air temp. Has to be a minimum flow past the thermostat to 'tell it' the temperature but this is only a 1.5mm hole in the back plate, might work on this in the future. Ignition is very stable and good spread of power now the ECU isn't having to compensate for erratic coolant temp. No leaks but filling up coolant took a while since there is the possibility of an air-lock around the thermostat. Winter running is often problematic but looking forward to summer.