New Water Pump or Just Low Coolant Level, What Does It Mean When?

[Michael K]

On the 1988 300SL (R107, M103) the low coolant idiot light has come on twice in the last week. Both times it's been while going around a long, sweeping turns with high lateral forces. Both times, as soon as I exited the turn, the idiot light went out. The only symptom is the idiot light coming on twice, both times briefly (only while in the high load, extended turn). Is it time for a new water pump or is it something simpler like the system not holding enough pressure (like from a worn out expansion take filler cap)? No other symptoms other than the brief idiot light.