Discoloured coolant, rust?

[prelude]

Recently I noticed that the colour of my coolant had started to change. I reckoned it was time to replace the coolant and this dropped it all and decided to clean the radiator in the mean time. A bit of mud in the bottom from offroading that needed to be removed so what the heck.

When the coolant was all out I noticed how the radiator looked a bit brownish, I flushed it with a hose and a whole heap of rust started coming out! This worried me somewhat since I had the coolant and radiator replaced when I got my rebuild engine ie. everything was new and clean, including the water pump. The only thing I have not touched is the heater core but I would not think that to contain or cause so much rust. I never topped up with water and the system did not have any leaks. How on earth can all that rust be in the system, what can I do about it and how do I prevent it?!

Cheers,
-P

[Tombie]

How olds your coolant?
Have you topped it up at all since it was changed? And if so with what?
What coolant did you use?
What radiator are you running? Alloy or Copper?

[prelude]

The coolant would be coming on close to 6 years old and around 50K's driven.
I have topped it up at most with a few hundred mil if that with the same coolant I filled the system with
The coolant I used is the recommended stuff from kroon (local brand) here is a link: Coolant -38 Organic NF productinformatie. - Kroon-Oil (https://www.kroon-oil.com/en/catalogue/product/185/coolant-38-organic-nf/103/)
I have an alloy radiator.

PS I use the same coolant in my alloy honda engines without any trouble whatsoever. :confused:

-P

[Tombie]

I note that it specifies a 3 year replacement period :)

I'd suggest it had lost its effectiveness

[prelude]

[bigwhistle] I missed that one, then again, the car did not move during lockdown but I guess it's like food: it just stops working eh?

Well, here is hoping that it will stop further rusting and I'll put a reminder in my agenda about the age of the stuff!

-P