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.

Exhaust Clamp Tested and Rad Fan Switch Changed

Ran the engine again, this time with the silencer clamped to the cat pipe.  No leaks, so that job is done.

The radiator fan switch supplied by Tiger activates at 84oC.  This is a bit low for the Zetec on fuel injection so I always thought that I'd have to change it over to the higher setting.  Anyway, when I looked at the higher setting it was about 147oC so obviously no use!  I bought a replacement switch (Intermotor 50102 - for Peugeot 205/Citroen BX C15).  The lower setting comes on at 93oC and goes off at 88oC.  The higher setting is 97oC/92oC.  I installed it on the radiator and checked it in operation.  It seems to work okay.

As I have no thermostat installed I need the fan to operate at the correct temperature.  While running the engine with the car stationary the Tiger ali radiator seems to be very efficient at cooling.  I'll have to see how it performs when the engine is working harder on the road.  I may have to watch out for over-cooling, especially in the colder months.

Cooling System - Mark 3

When previously installing the Tiger alloy radiator I re-used the 'puller' fan that I had bought for the Polo radiator.  This meant that the radiator could not be angled back fully all the way to the upper horizontal chassis rail.  Now that I'm able to trial fit the nose cone I can see that the top of the radiator is not low enough.  Time to replace the 'puller' type fan with a 'pusher' type.

With the radiator angled all the way back to the chassis rail the nose cone now fits properly.

The water rail was attached to the side chassis rail.  A dab of Sikaflex and a rivet at each end have made a strong mounting.

Radiator Change

While at the Tiger at the weekend I discussed my plans for engine cooling.  Weighing up the pros and cons of the Polo radiator I had a change of mind and a further lightening of the wallet.  My car (is it a car yet?) is now adorned with a shiny alloy radiator.

This new radiator choice has also simplified the plumbing.  Now I'll just be using the two 32mm hose connections on the thermostat housing to the radiator and the 15mm connection on the bottom of the rad to the expansion tank.  Both heater outlets on the thermostat housing will be blanked and the centre of the thermostat removed.  It will take slightly longer to warm up, but as the car will not be used on very cold days it should not be a problem.

I've kept my 'puller' fan, but it means the rad has to sit a little high.  I will only know when I get the nose cone on.  There is probably a bit of room to move the rad lower with some slight tweaking of the mounting brackets.

Polo Radiator Fitted

Some simple brackets made up from 5mm steel strip.  B&Q had exactly the right piece of steel available from which to cut these.  The brackets were given a quick couple of coats of Hammerite.

Lightweight (tinfoil and plastic) Polo radiator fitted and fan mounted.  I decided to go for a 'pull' type fan in the end. This leaves the front of the radiator free for fitting an oil cooler later - no plans at the moment though.

The 12 inch fan fits in very nicely behind the radiator.

The radiator was mounted at angle for two reasons.  The first, as I don't yet have the bodyshell on I don't know how much space I have to work with, so erred on the safe side.  Second, if mounted vertically both the pipe openings clash with other things (steering rack and upper chassis rail).

The fan wiring will be connected once the wiring loom in the engine bay is properly routed and mounted.