Any views/comments would be appreciated.
Hi Geof. I can concur that blocking my rad also appears to aid cooling. I had some strange goings on in my coolant system. It could just all be conjecture but I put the cause down to the coolant flowing backwards in the Duratec compared to a normal engine.
Stumbled across this a while ago whilst trying to work out why my little engine with its big Plus 8/Roaster radiator ran so hot all the time. I had been scratching my head for ages trying to work out why the cooling fan was often running with the engine cooking yet my thermostat was closed with the bottom of the rad staying dead cold. Strangely this was more so in cold weather. Sometimes the stat would not open until the engine was way beyond 100C (reading from ECU not the useless dash ornament). I’m no auto expert but this is my attempt at an explanation ….
I’ve noticed that the thermostat on my Duratec doesn’t necessarily open at a fixed predefined engine temp. The point at which it opens is dynamic with respect to the cylinder head engine temp. This might have something to do with stat’s location and the fact that coolant flows in the opposite direction to a conventional engine that I am more used to. The dual valve stat is located down on the engine’s coolant input rather than at the top on the hot output (see below). There is both the hot bypass coolant and the cooled rad coolant flowing into the stat housing so the stat appears to be controlled by the combined heat from both.
Not my motor but here’s a pic of how the coolant paths converge at the stat housing
There is a kind of perverse inverse cooling relationship going on with this engine, I think… The lower the temp of the coolant exiting the rad, the higher the engine temp has to reach before the coolant in the stat housing is hot enough to open the stat. And what appears to makes the stat opening point so difficult to predict is that the rad temp is effected by at least 3 variables. The speed of the car or the air flow through the rad, the external ambient temp and efficiency of the rad. I suspect that for this system to work optimally there is fine balance and I think that my big ali rad was over cooling. My cooled coolant appeared to be inhibiting my stat causing it to open late.
In an attempt to open my stat sooner (or at a lower engine temp) I have de-rated my rad to raise the output temp of the cooled coolant exiting it. I have played with blocking off different amounts and now I think I have it optimised. After driving around for ages with a thermocouple stuck on the rad output and an OBD reader displaying the head temp it looks very well behaved. My Burton Power 82C stat (standard is 90C) is now opening and regulating the engine temp well in advance of the cooling fan cutting in. The ECU reports the engine temp now stays down in the mid 90’s with the occasional spike over 100C when the foot is hard down or belting up a hill. Last year’s 30C plus summer weather was a good test too as the engine temp stayed remarkably steady and consistent with out the rad fan kicking in despite the rad airflow restriction.
Here is my ‘run cooler’ baffle
Baffle sprung/fixed in position with PTFE feet. Air flow restricted at the top. The baffle is spaced off a little to allow the cooling fan to draw air through if required.
I apologise for the ramble
