Description: The reservoir, or expansion tank as it’s sometimes called, is a semi-transparent plastic bottle that may be pressurized or non-pressurized. The reservoir usually has level markings for quick checking of the coolant level.
Purpose: The reservoir allows for expansion of the coolant when the engine is warm, rather than having the coolant spill out of an overflow tube. When connected to the radiator with a properly functioning pressure cap, the reservoir enables the radiator to be consistently full, regardless of temperature.
Maintenance Tips/Suggestions: Check the coolant level at least every oil change; weekly is even better. A reservoir that consistently drops in coolant level after topping off usually indicates a leak. The hose between the reservoir and radiator may be loose or damaged, the pressure cap may be faulty, or there may be a leak elsewhere in the cooling system. If your inspection of the system provides no clues, have the cooling system pressure tested and checked by a qualified professional.
