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I am planning on replacing the coolant in my 37, 120 and would like to know if I can use a radiator flush product like Prestone before replacing the coolant. Are there any metal or other concerns in these old engines that would preclude using a modern flush?

thanks for your help,

Rod

I know of no reason why you couldn't use it safely. But for a really effective cleaning and flush, especially if there are any rust deposits in the block, I'd rather try to duplicate the old NLA DuPont 2-part cleaner that utilized oxalic acid, followed by sodium bicarbonate as a neutralizer. Oxalic acid is particularly effective in dealing with rust residues.

Rod,

I don't have a recommendation on the type of chemical to use in flushing the cooling system, but do recommend that you back-flush the block, radiator, and heater (if equipped) separately. I recommend this method in order to keep the debris from the engine getting into the radiator and heater cores and plugging them.

Easy enough to do, just remove the radiator and heater hoses and flush the block by inserting a garden hose into the water outlet on the front top of the cylinder head after removing the thermostat (if equipped). Flush the radiator from the bottom. Probably does not make much difference which way the water flows through the heater core.

When through it is a good time to replace the hoses and thermostat with new ones.

Others here may agree or disagree, or have other suggestions.

(o[]o)

Just excellent advice from JW. Here's a snap of the flushing gun I've used often with good results. It uses fresh water pressure from a garden hose and turbulence from compressed air blasts. A nice flea market find for a couple of bucks.

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