Heating Up When Stationary

[MarkDa]

Going back to water circulation I've noticed that on a standard system if I stop the engine when temp is 100c with the electric fan running within a few minutes the temp will fall to 85c.
There's obviously thermo-syphonic circulation going on without the pump running

[Craven]

What effect does turning the heater on, this will change the flow around the thermostat and sensor housing.

[disquek]

I assume that the fan on the front of the rad should be drawing in air from the nose of the car and pushing it towards the engine??

I'm not convinced that this is the case. Especially with rad mounted fans (as opposed to the un-shrouded OEM fan that was closer to the nose/grill).

Fans will pull air from the path of least resistance. Which is typically the shortest distance. The rad mounted fans are closer to the engine bay than the nose/grill. So when sitting still, I'm thinking a decent percentage of air that's coming into a rad mounted fan is coming from the engine bay.

This is where the design and size of the Elan engine bay is the issue and why the wheel well vents help.

Blocking the open area surrounding the rad seems like it might help to increase the percentage of "fresh" air from the nose/grill that the fan sees.

For what it's worth, on our race cars we'd make tin work to shroud the radiator all the way to the nose/grill preventing any possibility of the radiator seeing air from the engine bay. Far easier in a tube frame race car than in a very complex shaped OEM car. And the point of doing this wasn't the thermal runaway that we're considering here. It was to make sure that all air that got under the car was "used" for cooling and thus generated the least amount of lift from under hood pressure.

[MarkDa]

I'm not convinced that we are looking at thermal runaway.
The OP says temperature indicator rises to 105.indicated but radiator doesn't go above 90c and engine doesn't boil.
The fan is in front of the radiator and with seals all round the radiator surely the line of least resistance for air to the fan is from the nose?
With the radiator sealed there is a ram effect on the radiator because of that seal hence very good cooling on the move.

[William2]

There are a lot of Elan owners out there who have gone down the route of fitting a wide alloy rad for various reasons. I never realised that there was a downside with using different metals in the cooling system. Does that also mean you shouldn't use standard antifreeze? I find it hard to believe that my rad is choked up with much rust sediment which I guess would potentially come from the block.

[gus]

I am not convinced you have a problem

If the temp is not running away, 105 degrees is not a problem

Aluminum radiator is no more a problem than the aluminum head

fresh antifreeze is a solution to corrosion

[MarkDa]

Quite agree.