Hey guys, I have a 95 3VZE 4X4 that is getting hot for no apparent reason. I was driving in town in stop and go traffic and watched the temp needle jump up close to the red. as soon as i started moving again it went back down, but the next red light i was sitting at it shot back up. I pulled over and took a look under the hood. everything looked fine, no steam, no lost coolant. I started driving again and it was fine all day, even at idle. then a couple days later it did the same thing while at idle, except this time i shut it off and heard hisses, like coolant hitting the headers. but again, no steam or lost coolant. I tried diagnosing the problem today, so i let it idle in the driveway for about 10 minutes and the temp never went past half way! the water pump is exactly a year old, the rad is 2 years old. is the thermostat or rad maybe clogged? Also, the heater only blows hot air when im driving. sitting at idle it only blows cool air. should i drain the coolant and replace with new? is there a way to bleed the air out, maybe there is a void somewhere in the system. thanks for any help.