The temperature was minus 4oC this morning after 3 days of heavy rain, flooded roads and now snow. The car was last used yesterday evening without a tyre pressure warning and was parked overnight under a 3 inch blanket of snow which was the very devil to remove this morning . It was no longer fluffy snow - instead solid aerated ice.
When I started it, I got a low tyre pressure warning on just one tyre - 24 psi when the other 3 were reading 36 psi.
I inflated it to 36 psi, went shopping, and the pressure on all 4 tyres crept up to 38 psi after driving 5 miles - which is normal behaviour.
I returned home 4 hours ago and all 4 tyres are still reading 36 psi.
It would appear that the errant tyre does not have a puncture so I am not sure what caused the considerable loss of air.
My only thought, probably crazy, is that water got inside the valve cap - it froze overnight, the trapped ice expanded, and pushed against the valve spindle. Thus releasing air
Is this really plausible?