i've had my car on the road for a year now, and haven't had a problem with the exception and replacing a thermostat and having to top off the fluid with a cup of water from time to time. i hadn't seen any leaks, and the temp has been fine. lately, it's still been running about 180, but when i stop, coolant comes pouring out of somewhere. i'm 80% it's the overflow, but it's been dark the two worst times it's done it, and i couldn't get under it to see the source. it just pours out about 12 ounces or so and stops. then, it gets a little hot if i just let it sit and idle. i top off the radiator, and it seems fine again.

i took the cap off the radiator and idled hoping to try to get it all full. as it sat there running, it began to force water up and out of the filler hole. there has to be an air pocter in the engine somewhere because i spilled out much more that it wants to hold. i had to deal with an air pocket right after i first started the engine, but it got really hot quick, and this hasn't been the case.

why is there so much pressure in the system, and why is it spilling out at 180 degrees?