Coolant system a3 1.8t 8L

[Derren]

Hi when I purchased my Audi A3 1.8t 2001 (about 3 years ago) I noticed the coolant was a rusty colour. Drained the system and washed through with a hose until clear, but didn't run engine. Filled with g12 and it's been fine

but I noticed it has gone a rusty colour again, I have now drained it again and flushed with water and running engine until warm about 5 times but keeps coming out the same colour. I have changed the radiator hoses and expansion tank now and the old tank has got a brown gritty substance in the bottom,

when I hold a magnet to it, it attracts to it!! I am guessing someone has been running it with just water? Does this mean there is internal damage or can this be flushed out eventually? It doesn't over heat and the grit isn't oily its rusty. Thanks

[Das Ponto]

Hmm that definitely is a bit of an odd situation to be having. If there is no mixing into the oil I don't see what exactly that could even be. Could be coming from the Rad itself perhaps?

If the system is still contained (not getting into the engine, which would cause milky residue in the oil) then there are only so many places it could come from. The water only could be a possibility perhaps?

Now that you have flushed it really good and replaced a few items perhaps see if it continues first? Then more investigation will be required of course.