coolant problems

2000 Chevy Blazer. I have recently been loosing coolant through the overflow. Does this mean that I should replace the radiator cap? The coolant temp is fine. Also the cap I have is plastic and says closed system and is rated at 15 lbs. I looked up the cap on the Napa web site and they list a 16lb cap.Is it alright to use a higher rated cap? Any input please. Thanks

Is the coolant coming out the top of overflow tank or is there a hole in it or is the hose leaking?

Has the coolant ever been changed?

Yes get a good rad cap first thing.
Use what the book calls for on the lb of cap.

The coolant comes from the overflow tube. The coolant hasn't been changed since I have owned it. Is it OK to use a 16lb instead of a 15lb cap?

Use what Oem chev parts specs call for.
If the coolant has not been changed it may be a good time to change it.
M