The most common use of a pressure cap is on the cooling system.
This is to allow :
another location are the fuel cap on most modern cars and trucks.
On a 1994 Lincoln Town Car : The thread on cap on the engine coolant reservoir is the pressure cap / radiator cap
On a 1997 Lincoln Town Car : The thread on cap on the engine coolant reservoir is the pressure cap / radiator cap
On a 1994 Lincoln Town Car : The thread on cap on the engine coolant reservoir is the pressure cap / radiator cap
On a 1994 Lincoln Town Car : The thread on cap on the engine coolant reservoir is the pressure cap / radiator cap
On a 1997 Lincoln Town Car : The thread on cap on your engine coolant reservoir is your pressure cap / radiator cap
On a 1993 Lincoln Town Car : The threaded cap on the engine coolant reservoir is the pressure cap / radiator cap
On a 1999 Lincoln Town Car : The thread on cap on the engine coolant reservoir is your pressure cap / radiator cap ( 16 PSI )
On a 1999 Lincoln Town car : The thread on cap on the engine coolant reservoir is your pressure cap / radiator cap ( 16 PSI )
Either the cap is defective or too much pressure is building up in the system. I would replace the cap is it does not appear to be overheating. answer you have a defective radiator cap replace with a new one with same pressure rating as old one
You attach a pressure test kit to where the radiator cap goes, and pressurize the system. If it holds pressure, it's good.
Apply a downward pressure on the cap while twisting it counterclockwise. When the cap assembly is off there will be an opening, this is where you stick the pump nozzle to put gas in the car. Be srure to replace the cap when finished. Apply a downward pressure to the cap assembly while at the same time twist it counter clockwise, the cap assembly will come off at that tiem leaving the fill tube opening exposed. This is where you place the pump nozzle to put gas in the car. Be sure after fueling to replace the cap assembly!
On the rightside of the car. The low pressure line with the blue cap.