You don't. The water is pressurised to 13 lb/sq in and 90deg C. If the cap is plugged ther is no safety pressure relief and the cooling system can explode. Without the pressure cap the water boils off and damage to the engine is inevitable. Get a new one
If you have a threaded cap on your coolant reservoir that is your " radiator cap "
No , the " radiator " cap / pressure cap is the thread on cap on the engine coolant reservoir
The radiator cap is on top of the radiator.
the radiator cap is on top of the radiator you idiots
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 )
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 radiator cap is located on top of the radiator.
On a 2004 Ford Freestar : The thread on cap on the engine coolant reservoir is the pressure cap / radiator cap
where is the radiator cap on a 2002 tribute
The thread on cap on your engine coolant reservoir is the pressure cap / radiator cap