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    Ben Stevens

    I’ve already flushed out the cooling system with water but am thinking it might make sense to use a proper flushing solution before filling up?

    Any recommendations for such things?

    Also, what coolant can people recommend?  I have the volume required at 4.5 imperial quarts, or just over 20 litres – does that sound about right?

    Tim Wilson

    Hi, Ben: l just use a Halfords antifreeze – the blue colour, which suits our old cars better.

    Last time l filled my Special’s cooling system from scratch, it took 32 litres! Mine is the stock Ford Pilot flathead.


    Ben Stevens

    Wow, 32 litres!!  Is that 50:50 antifreeze to de-ionised water?


    I am advised that the more antifreeze the less cooling efficiency so put in just sufficient for the temperatures the car will likely encounter.

    De-ionised water is better than tap.



    Frost Restoration produce a very good flush of their own.

    They have an excellent range of car restoration products – highly recommended – by me!


    Neil Bennett


    I think you meant 4.5 Imperial gallons, rather than quarts, ie. ~20 litres. The Ford flathead engine is the quickest way I know of boiling four gallons of water so internal cleanliness is important – use a commercial chemical scourer when the engine is running – heat is required for a good clean-out. Then add a surfactant like Water-Wetter to reduce the surface tension to the block internals.

    Unadulterated plain water is by far the best coolant (with a surfactant). However, if you are not going to over-winter your car in a heated garage or drain it and lay it up, then anitifreeze is essential, 35% minimum, but the type of antifreeze is important.

    At risk of teaching granny to suck eggs, and for the avoidance of doubt I offer the following descriptions:

    Most commercial antifreeze formulations include a glycol (to suppress the freezing point and raise the boiling point), corrosion inhibiting compounds and a coloured dye (commonly orange, green, red, or blue fluorescent) to aid in identification. A 1:1 dilution with water is usually used, resulting in a freezing point in the range of minus 37 °C to minus 42 °C, depending on the formulation. There are two basic types of antifreeze available today dependent on the corrosion inhibitors used:

    Inorganic Additive Technology
    This is the traditional coolant based on inorganic additives and is called inorganic additive technology (IAT). It is a tried and proven chemistry that provides a fast acting protective film. The additives deplete and the coolant needs to be drained and replenished every couple of years. This type can be used on all mixed metal engines with components including steel, cast iron, copper, brass, aluminium and solder without any detrimental effect.

    Organic Additive Technology (neutralised acids)
    The newer OAT coolants work differently than the older silicate based IAT coolants. Aluminium and ferrous metals form a surface-layer of corrosion in the presence of moisture, even with the little bit of moisture in the air. OAT coolants prevent this metal-oxide layer that protects the surface against this corrosion. Inherent with their design, the OAT coolants last longer than the older traditional IAT coolants.

    This category of antifreeze cannot be used in systems containing yellow metals.

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