Definitely worth reading this post Nick.
https://www.talkmorgan.com/ubbthreads.php/topics/834133/1For cleaning my plastic header tank I used Sterident tablets, actually I tried many different chemicals including drain cleaner, however, the Sterident tablets certainly worked best
Before embarking on the cleaning process I would see how much a brand new plastic header tank is on eBay, there are lots of options available for very little money, you just need to establish what car the original came from? For example, a brand new tank for my 2012 Duratec Plus 4 was less than £20, I belive it's for a Mk1 Ford Focus. Given how cheap a new one is, and had I not been so succesful cleaning my original with Sterident tablets, I definitely would have just replaced it.
Prestone coolant is the way forward in my opionion, they also offer a good flush treatment that works really well. Obviously the Prestone flush chemical is compatable with their coolant, so if you do the full Prestone flush and refill process with their coolant you know it's done right, you're also left with a cooling system that doesn't need another coolant change for a full 10 years
Dave.
