To raise the boiling point of the coolant.
A lot of vehicles don't have the radiator cap on the radiator , they use a thread on style cap on the engine coolant reservoir ( that is the pressure cap / radiator cap )
Look for a radiator cap and add it there.Look for a radiator cap and add it there.
No , the " radiator " cap / pressure cap is the thread on cap on the engine coolant reservoir
The thread on cap on your engine coolant reservoir is your pressure cap / radiator cap
The thread on cap on the engine coolant reservoir is the pressure cap / radiator cap
The thread on cap on your engine coolant reservoir is your pressure cap / radiator cap
The thread on cap on the engine coolant reservoir is the pressure cap / radiator cap for the engine cooling system
On a 2001 Ford Focus : The thread on cap on your engine coolant reservoir is the pressure cap / radiator cap
The engine coolant reservoir has a thread on cap which is the "radiator " cap for the 4 cylinder engine
The thread on cap on your engine coolant reservoir is the " radiator " cap
Remove the radiator cap ONLY when the engine is cold.
If it is an air cooled engine then it will not have a radiator cap.