Friday, 30 March 2012

Reintroducing a Thermostat

As I am not happy with how the cooling system is working (over-cooling) I am going to re-introduce a thermostat.  One option is to add a lower water rail and connect this to the bypass outlet of the thermostat housing.  Only problem with this is that the sensor for the coolant temperature is mounted in the main cooling pipe and would not read properly, especially during warm up.  I've read that the thermostat housing can be drilled and tapped so that the sensor can be mounted here, but I don't want to take a chance trying to do that with something made of plastic.

In the end I've gone for the option some other Tiger owners have adopted: a thermostat with a bypass hole for the warm-up phase.  I've used a 88oC thermostat from a Ford Focus 1.8 diesel (part # QTH316K).  Prior to fitting a 4mm hole was drilled through the outer edge.

The Tiger provided radiator fan switch was a 87oC type, so that was changed for one that operates at 92oC (Intermotor part 50200, used on Alfa 33's, Audi 80's, etc.).  I took the car out for a spirited drive yesterday afternoon.  55 miles approximately.  Once warmed up the coolant stayed very steady at 88oC.  When I stopped in traffic it rose to 92oC, at which point the fan was running.

So far I am very pleased.  I'd just like to test the car in colder and warmer conditions, with a bit of time stationary to make sure it's not going to get too hot.  I've got the temperature warning light on the Acewell digital dash set to 95oC so that should alert me if there is a problem.  There's also a coolant overheat warning displayed by the ECU warning light.  This is via the temperature sensor that is screwed into the engine block.  I don't recall at what temperature this activates.

During this whole process one thought did occur to me: if your car does not have a coolant warning light it would be easy to add one by using the second (higher) temperature setting on a dual-temperature radiator fan switch.

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