Will it work? What are the dangers?

[T-Cut]

Originally Posted by Heddy

Replying to a 'blocked matrix' thread, I thought I might break into the heater hoses and tip a bottle of kettle descaler in. Pure madness? Or could it actually work? I've tried rad flush with no improvement. Your thoughts please.

If a standard hose flush doesn't work and you want to keep the matrix if possible, then kettle descaler is the way to go. Descalers contain strong acids like propionic along with inhibitors to stop it attacking metals. This dissolves the calcium carbonate scale releasing carbon dioxide. It won't harm the matrix per se, and will shift a lot of the bound-on scale. If a potential leak is being sealed by limescale, then the matrix is scrap anyway.

Logically, heater matrix scaling to the point of blockage is the result of hard water top ups to a cooling system that's not fully watertight. Obviously, using deionised/distilled water is ideal. Scaling won't happen so severely in a watertight system with the correct coolant formula. Antifreeze contains calcium ion sequestrants to minimise limescale formation, even when using hard tap water. It's similar to Calgon in washing machines - a preventive but not a cure.

Limescale deposition is a temperature dependent equilibrium reaction between calcium bicarbonate, calcium carbonate and carbon dioxide in solution. Carbonate and bicarbonate are more soluble (safe) in hot water than cold, so the matrix tends to focus scale deposition because of the falling temperature across it. The antifreeze keeps the balance to the soluble calcium side of the equation, minimising the problem.

TC

[Heddy]

Thank you, some great answers. I was just concerned about the effect of descaler on rubber hoses, after all, it is a form of acid. Gonna do it

[T-Cut]

Most rubbers are resistant to acids - certainly the ones used in kettle descalant. But without removing the matrix, I'm not sure you'll get adequate contact unless you have a gallon of it.

TC

[roverbarmy]

Take off both rubber hoses. Pour in via highest hose using a funnel until it starts to leak out of lower hose. Lift each hose in turn to move descaler back and forth. Plug ends of hoses with a cork and leave to stand as long as you dare! Drain into a plastic bowl from lowest pipe. Backflush with water via a hose pipe. Refill and bleed system to test. Save the drained descaler/flush in case it needs another session. ( I hasten to add that I have never done this on a Rover but have done it on several other vehicles to good effect.)