Vinegar.

[AlanS]

I was treading fairly cautiously as I had a part that was alloy around the thermostat region and was obviously scummed up pretty badly, so I began by just bunging the holes and filled with vinegar. After a day or so, if you rubbed it hard with your index finger, it seemed to just slightly discolour the liquid. I kept a close eye on things in case it started discolouring or showing any other signs of chemical reaction, but when I poured it out and wiped it over, there was not enough effect to make it appear viable. I had also filled the radiator at the same time and found if I ran my finger around the neck where the hoses fit, then a bit came off. When I gave it a couple of hits with bi-carb being added, that was when the results got spectacular.
I'd say as has been suggected, a combination of a sudden change to the ph coupled to the agitation caused by the foaming does the business.


Alan S

[Brian]

Hi Alan,

It seems that you have used the vinegar straight from the bottle, on parts off the car.
Like most chemical reactions they work faster when the temperature is increased.

So with cooling systems, they have to be run up to temperature, then you will observe the effect.
May require 2 or more applications to get any benifit, left in for a couple of days or more, drained, flushed and refilled with new vinegar/bi carb.

If the system is seriously scaled up, then this method will be of little use.