Car is a standard Caterham Roadsport A 1600 K series.

In the current ambient conditions of 0º to 4ºC on a medium to hard run on the road the oil temp never goes above 30/40º and the water temp is similar.

I took advice that in really cold weather to block off part of the radiator so i put a piece of card half covering the nose cone grill. Took it for a drive and low and behold the oil will reach 70 to 100º depending on how hard the driving is. The water will head northwards of 100º and when the fan kicks in the indicated water temp on the Caterham gauge is about 110º. The fan drops it to an indicated 100º or thereabouts before cutting out.

My questions are:

It seems I might not actually have a stat fitted? Being an ex race car what are the chances that it has had the stat removed? It might be the reason that it doesn't warm up (when I don't have card over the nose)?

Is my fan switch coming on at too high a temperature? A lot of what I've read has mentioned that people like to have temps holding around 80º but at the moment I'm all over the place depending on what I do.

Thanks,
Oli

i would check your thermostat, sounds like it just either always open, or, like you said, not there at all.

Yeah logically sounds like that is the issue. The racers seem to remove the stat firstly as its one less thing to go wrong and secondly when you're racing things heat up very fast anyway which negates the need for a stat?

Either stat stuck open or not fitted. Rather than fit the standard one behind the pump, you might be better off fitting the later in hose type. British Triton is your man for more info.

You may find that the cardboard trick might be the best winter option, and when the weather warms up again things will revert to normal. My polo rad seems too efficient for my V6 in winter and I need to block some off to get normal temps back. In the summer its fine though.

Normal thermostat temp for the K series starts to open at 88c but coolant the thermostat has little effect on oil temp, with the alloy sump the oil temp tends to stay very cold in winter weather. In its natural Rover habitat the K series has (or at least leaves the factory with) an undertray that covers most of the sump and makes the oil run at significantly higher temp.

Because of the low oil temps I usually recommend fully synthetic a 5w40 or 5w/50 for engines that get hard use or a 5w/30 synthetic pottering.

The cooling fans when installed in MG-Rovers are controlled by the ECU only cut in at full (3rd) speed at at an alarming 115c.

It is possible your car has a thermostat fitted but it is either a lower temp stat fited and/or has been drilled.
The best thermostat for the K series is to convert to the PRRT from the Landrover TD5 as this allows the thermostat to open when the engine is revved hard even if not up to full temperature.