So yes, it's somewhat akin to -and indicative of- 'cold' and 'hot' on other vehicles, but is strictly a volume situation. As it expands, coolant will flow into the reservoir, then be drawn back into the engine as it cools off and its volume is reduced.
Ideally, it should never fall below the 'MIN' mark nor ever rise above the 'MAX' mark on the reservoir, but it WILL rise and fall as its temp rises and falls. At the risk of sounding too much like a know-it-all teacher (yeah, I was one, sorry).Īs far as I know, all cars these days (and most, since the 1960s) have coolant overflow reservoirs, as coolant will expand when it's heated up as the engine runs.
