e39 - White smoke when driving in freezing temps

[Arma 134]

Drove up to Turoa on Wednesday - it was below 0 and snowing quite a bit. I noticed when going up the hill some white smoke started coming out of the engine bay. Opened the hood up, saw and smelled the smoke, but couldn't notice anything else out of place except a little bit of spray (looked like coolant) on the air intake box, which generally happens when coolant falls on the belt and it gets sprayed onto the intake box - this never really happens any more since i've done my cooling system earlier this year. I let the car sit at the car park all day and checked coolant levels when I was leaving - everything looked fine. No smoke appeared going down the hill and I can't figure out wtf it was that caused the smoke going up hill. My entire cooling system is new, almost every single pipe, house, radiator, thermostat, pump etc. so I don't think it should be leaking. I also did the 4 hour drive back to Auckland yesterday and checked all levels this morning - no sign of coolant leaks or anything.

Any idea what could have triggered white ish smoke (it smelled too) when going up hill? Anything to do with the cold temp?

[lord_jagganath 421]

was your a/c running? with the heat and a/c on at the same time?

[Arma 134]

was your a/c running? with the heat and a/c on at the same time?

Yes

[Lubed 55]

Those last few kms up to Turoa are quite steep and engines are working hard, producing high exhaust temps. Possible current or previous oil leak burning off hot exhaust manifold?