[csd]

I have 2003 pt touring.
Today i drove about 10 min and came to a traffic jam, after about 5 min in the jam, i got the grugling sound under the hood, near the drivers side, the temp started going up, but not to a dangerous point, just 1/4 over the middle on the temp gauge, luckly the traffic jam got away so i kept driving, now air flowing in the rad, temp dropped fast, to test it i parked letting the engine run for a while, hit the gas to get the temp, up and nothing all seems fine.
In other ocasions i've been driving a lot over 3 hrs and in heavy traffic, and no problems, last year this has happend about 4 times, but the temp has never gone up to the red zone, no steam pouring our of the engine, no serious problems, i do sometimes get a bit low in coolant but no badly, checked for leaks , there seems to be no leaks.
My guess would be that is has something to do with the thermostat getting stuck, or the rad fan, or maybe i have air in the system.

I'll check the rad fan with the A/C on
Can someone point out where the thermostat is so i can check it out.
And where do i drain the air from the cooling system?