I checking over the 2003 Forester in the garage, and shut it off after checking automatic transmission fluid level. I heard a dripping sound from underneath and saw a small puddle under the transmission pan. I put it up on Jack stands and got underneath, but the dripping had stopped. I confirmed it was engine coolant but looking up underneath, I couldn’t determine where it came from. My first thought was from a heater hose, since it was from that general area, but both heater hoses were clean and dry (they were replaced 5 years ago). Also no indication of leaking from the heater core. 

Not sure where else to look for coolant leaks near the rear of the engine. Are these are any other small coolant hoses on the EJ251 engine? I recall my old EJ22 had a small coolant hose that ran to the IACV. Not sure where else to look for coolant leak from that part of the car.

Check the coolant level in the radiator, fill as needed.  Then pressurize the system, hand pump or let it run and see where it's dripping from.

I've had water pumps leak and run back along the oil pan lip.  That's a big leak, should be pretty easy to find.

Funny thing that I started and warmed it up a couple times after and no leak at all. I found the radiator was full but the coolant overflow reservoir was empty when it was cold again.

Coolant full? Then leaking on ground after driving? Then coolant-overflow reservoir is empty?

Unfortunately, this sequence points to an EJ head-gasket failure.

I figured it out the other day. I took another look at the heater hoses and there was wet coolant residue at the heater core ends of the hoses. The clamps weren't super tight, so i tightened them down (I replaced the heater hoses and used new clamps 5 years ago). I figured I was pushing on the heater hoses when accessing the transmission dipstick when I was checking the ATF level, and the loose clamps let some coolant leak out when the hoses were pushed on. I ran the car and even pushed on the heater hoses, but the connections to the heater core are still dry.

On 1/18/2024 at 2:45 PM, forester2002s said:

Coolant full? Then leaking on ground after driving? Then coolant-overflow reservoir is empty?

Unfortunately, this sequence points to an EJ head-gasket failure.

The reservoir has never overflowed nor has this car ever had an air bubbles in the reservoir with the engine running (I had two newer Foresters with internal headgasket leaks so I knew what to check for on this one)