Temperature control of the cooling system in my V8?

[Miel]

Recently I tried to understand the management of the temperature control of my engine.
The engine is a 4.0 litre V8 manufactured by TVR Power and installed in a Ginetta G33.
The radiator is a Ford Sierra Cosworth radiator (V86BB-8005-AB), which has the following connections:
1. The lower hose connected to the cooling water pump and probably transporting cooled water to the cooling water pump;
2. The upper hose connected to the thermostat in the inlet manifold and probably transporting hot water from the engine to the radiator;
3. A hose connected to the cooling water header tank; connection at the radiator is at approx. the same level as the lower hose, however, at the other side of the radiator;
4. Below this connection probably a radiator fan otter switch (temperature sensor?).

[/img]Sierra Cosworth Radiator.gif

[Ian Anderson]

First thing I would check is to disconnect the otto switch.
Short out the contacts in the wiring loom and tour fan should run.

If it does not run then you have an electrical problem.

Depending on what switch you have it could be that it makes an earth connection ( fan live is permanent) and when hot it makes the connection and the fan runs. If the switch is mounted in a hose or even on the radiator which is rubber mounted it does not make contact to the chassis / earth.

Ian

[Ian Anderson]

Next

If your fan runs, which way is it running?
It should move the air from the front of the car to the rear

If it is connected incorrectly it pushes air the wrong way.

Ian

[Miel]

Hi Ian,
Thank you for your reaction.
I shall try and follow your suggestions. The fan seems to operate normally. It starts running when engine reaches a certain temperature and stops automatically when temperature comes down, also when ignition is switched off. Furthermore, there is an override switch which also operates very well.
I am not an experienced mechanic nor electrically educated, so I may have to seek assistance as I do not want to ruin my present set-up, which now seems to work. The only thing now is that I try to understand the way it works and seek opinions whether it has been set up correctly. Your remark regarding the direction of the airflow puzzles me as well. I shall check that next week.
Kind regards,
Miel

[ramon alban]

Now, I notice three devices that somehow control temperatures:
1. The thermostat in the inlet manifold;
2. The radiator fan otter switch at the radiator;
3. The inline thermostat switch in the lower hose.

My questions are

1. Which device manages which system?;
2. Is the inline adjustable switch located in the correct radiator hose?
3. It is clear to me that you can not do without the thermostat in the inlet manifold, but what are the functions of the other two devices? And how do the interrelate?

Hello Miel, I am not at all familiar with the system you describe, so I can only address some fundamentals.

In response to the questions my understanding is an electrically controlled cooling system really only requires two controls. Thermostat and radiator cooling fan switch.

1) The primary purpose of the thermostat is to block the flow of coolant to the radiator until the engine has warmed up as fast as possible to minimize engine wear, deposits and emissions.

After that its next purpose is to block off the flow of coolant when the temperature of the coolant falls below the temperature at which it opened, if the combination of the radiator and the cooling fan are over-cooling the system.

In reality its not a true 'on or off' situation, but one that depends upon partial opening and closing of the thermostat to try and maintain a steady temperature situation.

So if - for example - an 88 degree thermostat is fitted one would expect the engine temperature to be maintained at something a little higher than 88 degrees, lets say 90 to 95 degrees - providing the cooling fan and radiator do their jobs properly

Of course the thermostat is not the only active component, it works in harmony with the cooling fan switch:

2) The primary purpose of the cooling fan switch is to make the fan cool the radiator if the engine/radiator temperature get too high (say) 5 to 10 degrees above the thermostat at 88 degrees.

The secondary purpose of the cooling fan switch is to switch off the fan to prevent over-cooling - again at a temperature perhaps equivalent to the closing temperature of the thermostat - give or take a little bit.

In reality this function is a true on/off situation and as a result fairly crude- unlike a viscous controlled fan unit that is more subtle in its control.

Conclusion - between the thermostat and the cooling fan switch the temperature of the engine and radiator should remain reasonably stable within a small range of (say) 5 - 10 degrees.

For the best possible control of radiator cooling effect the cooling fan switch should be located at hottest part, usually in or near the top hose inlet.

As for your third switch, I have no idea unless it is there to control the fuelling/mixture function of carburettors.

I can offer you some reading material in 3 articles I have written, that address the typically conventional RV8 cooling system as fitted to an SD1.

http://www.vintagemodelairplane.com/pag ... ing01.html

http://www.vintagemodelairplane.com/pag ... emp01.html

http://www.vintagemodelairplane.com/pag ... ant01.html

You may find further clarification of your temperature control issues there-in.

One of the issues you may have to address is to ensure the whole system is clear of deposits in the block/radiator/matrix that impede coolant flow.

Another issue may be that coolant flow is compromised by worn impeller blades on the water pump.