Need help with Coolant leak/overheating
My girlfriend has an 03 LE, really bare bones commuter car. She came to me today and said that her car had been overheating for awhile, I regularly check her fluid levels and the reservoir has always been full. she went to the store today, and when she came out she said there was coolant on the ground, but when she got home it wasn't leaking. I took it out to see when it was overheating, and its pretty general, but its worst at idle, however using the heater does bring it back down to normal. after I got back I parked and checked for any leaks but I didn't see any and the reservoir was still full. however I went to check on it maybe an hour later and there was some coolant on the ground, however again there was no leak an the reservoir was maybe a quarter inch below the fill line. the location where the coolant is hitting the ground is almost directly under the reservoir, I am confused on the leak, and why the car is overheating. I know the focus doesn't have a traditional radiator cap, but every car I have had has had either a locking cap on the reservoir or on the radiator, this cap seems to just screw on with no clicking or locking, is that normal?