[Mjr_Trbl]

I have a 1971 302 with rust in the cooling system. I flushed the system several times and the rust keeps coming back. Is there anything I can do or use keep the rust out?

[tripleblack]

The rust is coming from the iron block, heads and (probably) intake. This is a natural occurance, particularly on older cars.

If you flush out the whole system and fill with the correct mixture, that's about all you can do.

Some modern brands of coolant are ph neutral, which helps slow down the corrosion. Mercedes coolant is famous for this.

[SVT1995]

It coud be your radiator thats rusting from the inside.

[joe69]

Radiators are made of copper and brass, they don't rust.

Joe

[andrewmp6]

Make sure you use distilled water not tap water and they sell a coolant system filter too.Yes the rust is from the block and heads radiators are brass copper and alum none of them rust like iron.

[Tobben]

I'm using water with 50% coolant fluid. I don't have discolouring in my coolant water