What does a coolant reservoir do?
Furthermore, why is the coolant reservoir empty?
Constantly low on coolant If the reservoir cracks or develops any small leaks it can cause the coolant it is storing to leak or evaporate at a slow rate. The leaks may be small enough that they may not be obvious to the driver, however, over time they will cause the reservoir to empty out.
Also, do you need coolant in the reservoir? The reservoir has a fill range marked on the side. If your engine is cold, the coolant level should be up to the cold fill line. Loosen the reservoir cap just a little, then step back while the pressure releases. If the coolant level is low, add the correct coolant to the reservoir (not the radiator itself).
Regarding this, what is the purpose of a coolant overflow tank?
A radiator overflow tank collects the expanding coolant that is heated by the engine and recycles it back into the coolant system once it loses enough heat. The radiator overflow tank works in conjunction with the radiator cap to protect the engine and prevent coolant loss due to overflow.
Can you drive a car without a coolant reservoir cap?
If you drive without the coolant cap for any length of time when the engine gets up to temp it will boil over out of the reservoir. You will lose at least half of the coolant in the system if you drive like that for a few days.