[MadGus]

Recently, after a very spirited ~100 mile backroads drive in Virginia, I parked the Z4M and smelled what I thought was coolant. Closed garage, went on with life that day… next morning, the garage distinctly smells like coolant. No puddles or drips, engine bay looks completely clean, but the expansion tank level is close to MIN (float is up a little bit, but nowhere close to MAX). I’m suspecting a hairline crack in the tank at this point.

I have checked the coolant level every oil change and it has never needed a top up since I bought the car in 2019 with 45k miles on the clock. I have not flushed the coolant, and that was already on the list to do sometime this spring.

So, with that context, I have done a lot of preventative maintenance on the ‘06 Z4M which currently has ~76k miles on the clock, and am now wanting some advice about:

What level of cooling system refresh should I undertake prior to a ~2k mile road trip to the Smoky Mountains in two weeks?

1) replace all radiator hoses and expansion tank, flush coolant, keep driving with remaining original cooling system parts
2) above plus replace water pump and thermostat
3) above plus replace radiator with CSF 3055 all aluminum performance radiator

I have all of the parts on hand to do #3, and have the time these next two weekends to do everything, but I don’t want to prematurely change things if the consensus is that mileage is more important than age for these parts.