wich coolant?

[Ivan141]

Rust can only come from the engine with an alu radiator, so a flush is indeed a good idea. It takes quite a bit of flushing to get all the rust out, probably more comes loose when the engine is ran for a while. I havent ever heard of these cars needing any specific coolant, but just switch brands if you want to test your theory.

White sludge does not sound very promising, keep an eye out for other signs of headgasket problems. Rebuilt or not, cracked heads or a leaky headgasket will allow oil to leak into your cooling system, and vice versa.