Radiator Cap Pressure

Is there suppose to be pressure when I remove the radiator cap? I know its says 15psi but it never has any pressure, hot warm or cold. Does it matter? I run between 200 and 220 with no troubles. If I put a new cap on will it bring out leaks in the system? Just need ideas, leave alone or replace the cap and hope ,,, no leaks.

Is there suppose to be pressure when I remove the radiator cap? I know its says 15psi but it never has any pressure, hot warm or cold. Does it matter? I run between 200 and 220 with no troubles. If I put a new cap on will it bring out leaks in the system? Just need ideas, leave alone or replace the cap and hope ,,, no leaks.
i have a 95' aurora.when the motor reaches normal operating temp and i remove the cap,you can hear a loud hiss for about 2-3 seconds...i don't think theres any hissing when cold..try a new cap that won't hurt anything