saab 900 classic coolant

[gregcotier]

Mine is a 1992 model.
The coolant/water in the system is a yellow/brown rusty colour.
Is this how it should be?
I ask because ice caused it to split a joint in the radiator the other day in the alps when it was -20 at night.
I regularly top up with anti-freeze so was very surprised by this.
Greg

[Boosted LS1]

If you mix antifreeze types you could end up with a gloopy rust coloured mush. Or it could be corrosion from having had next to no antifreeze for a while. I'd be tempted to flush it all out and start again.