Montana 2003 radiator cap questions

Hi,
I am just looking at a Montana 2003 b4 buying but after checking engine, low coolant in reservoir, unable to remove rad cap, very tight even after pushing down on same.
Now there is 15 lbs cap on and want to know if I must use a 15bls cap or lower pressure one.
Any tricks to remove this stupid cap.

Hi, I finally remove my stupid cap and woul like to know if I should replace with a 15 lbs pressure or lower.
Hubmen

Hi, I finally remove my stupid cap and woul like to know if I should replace with a 15 lbs pressure or lower.
Hubmen

Replace with a 15 psi cap.

Be careful if removing the cap when the reservoir is full COLD (or full HOT) as the coolant will drain from the reservoir through the overflow hose. The coolant tank (reservoir) is higher than the rad cap.

HI, the reason the cap was hard to remove is that cap spring was dirty. Cap was changed with 15 lbs. Thank u.
Hubmen