Hi,

There's an old saying, "When you hear hoof beats, think of horses before
zebras."

Yes, it's normal for pressure to build up a little in time, and yes,
that pressure should be vented to the overflow tank, but let's remember
that Nature generally prefers the course of least energy expenditure, so
your coolant will find and try to escape from any tiny leakage point
BEFORE going to the trouble of traveling to the overflow tank. So:

Step 1--check the clamps and tighten as required...

Step 2--if that doesn't work, replace the hose. If it's the original,
it's very likely getting stiff and may not seal well. While the hose is
off, inspect the connection to make sure it's clean (no buildup of scale
and such) and not damaged. If it is, repair as required (as long as the
connections are smooth, I generally don't use sealer on hoses, but IF
there's some roughness due to corrosion, etc., one may benefit from a
sealer between the connection and hose. I've tried several that work,
but usually go w/ Permatex High Tack if the parts store stocks it.) If
you replace ONE hose, seriously consider doing them ALL at the same
time. It will probably mean time and money saved later...

Step 3--if neither of the above work, think zebras and start looking for
more complicated causes...

Good luck!

Rick