Morris Minor Owners Club

I'm refurbishing Vanessa's bits as I take them off , and have stripped the heater. the matrix is in reasonable condition, and appears not to be leaking, so I've flushed back and forward a couple of times, so it no longer runs brown. but i suspect there is still crud adhering to its inners ( one of the pipes was almost completely blocked with crud). Question is, what's the best for cleaning the radiator and heater matrix? Kilrock/ kettle descaler, citric acid, or other recommendations? it appears the heater matrix has steel headers and aluminium matrix, so i don't want use anything too aggressive.

It really depends on what the crud is. Descalers remove scale, degreasers remove oily deposits. They don't necessarily cover both duties.

You can ckeck if the matrix is blocked by running hot water through the cold matrix. If it gets hot quickly, there is no problem. Then it may be a case of "if it ain't broke, don't try to fix it"

Never tried it myself but hear cheap supermarket cola is good. Just fill it up and then rinise it all out a day or 2 later.

If you are not sure you can buy a brand new one for about 17 pounds on eBay.
Regards
Declan