Best way of cleaning / flushing a filthy cooling system?

[larrylamb11]

I'm working on a classic that's been imported from a warm dry state in the USA at the moment and whilst it's wonderful how all the bolts come undone and there's really no corrosion anywhere, the cooling system is woeful!
It's clearly not had any coolant change or maintenance of the system in decades and the stuff in it looks like mud soup.... I'm pretty sure it hasn't had any antifreeze and has been run on just water too.... it's properly grim......
Having pulled out the radiator and flushed and back flushed it on the hose I've finally got the water coming through the radiator running clean... but it's still pretty grim inside.... I'll complete the same process with the engine, flush and backflush, but what clever tricks and tips have people come up with to help flush cooling systems?

I will be putting it back together and re-filling with just water to begin with in order to keep flushing it through - run the engine, drain the water and crud, re-fill with fresh, repeat etc.. but is there anything anyone has found I can add to the water that will make a decent job of flushing out the crud and cleaning the internal galleries and passages? There is bound to be limescale build up to remove as well seeing as it has been run for years on just water...

Is there a cheat like Coke or denture cleaner or something?

[kimducati]

If it was me, I'd start with white vinegar. That'll work on the limescale in particular.
Do they still sell 'Radflush' in Halfords? Have a look at the tin if so, to see what the active ingredient is.
Kim

[healeyneil]

Haven’t tried it myself, but a dishwasher tablet is said to work wonders. Pop it in and run the engine for a while

[larrylamb11]

12L of white vinegar inbound.....

Researching proprietary 'flush' products.... If anyone has any specific recommendations, I'd like to hear them!

[paintman]

You could try: https://www.forteuk.co.uk/product/bio-degreaser-co...

[centralscot]

Citric acid?

[RazerSauber]

The go-to video for your situation would probably be ChrisFix

[MDMA .]

paintman said:

You could try: https://www.forteuk.co.uk/product/bio-degreaser-co...

Forte is good stuff. I always used it on MK2 Golfs (dreaded heater matrix) and they did the trick of unblocking them without removing the dash.

[v8250]

As above, white vinegar or a dilution of 10-15% critic acid and leave to work ~30mins. Then flush and reverse flush. Have used both before with equal results.

[Lotobear]

centralscot said:

Citric acid?

This is a very good recommendation. I recently cleaned a Ford (LTC) block that had stood full of water for 30 years. A strong citric acid solution worked brilliantly and removed all sludge and encrusted rust so that the water jacket looked like a fresh casting after a few treatments. Hot water helps when making the solution and leave it for at least 24 hours, flush and re treat.

The crystals are available from Wilko for a few quid.