Hey guys, I am brand new to the forum, so go easy on me. I used to be a member of F-Body.com back when it was still up and running, but hadn't really needed to post for advice till now.
Anyway, on to my problem, and I think it's a doozy. I think I may have done some severe damage to my motor. Some back history: The car is a 2000 V6 with 137,000 or so miles. I bought it new in 2000 and it has been great to me until the last year or so. I love the car, so it is breaking my heart to think it may be done. It has had some overheating issues in the past, and was going through coolant at a pretty steady rate. I never could see any external signs of leaks, but it kept wanting to overheat at random times. I took it in to be looked at, and the mechanic told me that he had pressure tested the heads and couldn't detect a leak, and said that it was low on coolant. He refilled it and it ran fine for a few months till this morning.
I have about a 30 minute commute to work, and at about the last 2 miles of my drive, it very suddenly overheated and blew the cap loose on the radiator. It quickly dropped back down to regular operating temp right after it blew the cap loos, so I limped it the rest of the way to work and parked it. I popped the hood to see that coolant had sprayed all over the engine compartment, and found that the cap was loose. So, I re-tightened it. Out of curiosity, I pulled the oil filler cap off and noticed the dreaded "chocolate milk" crud on the bottom of the cap. I had just done an oil change and topped off the coolant last night, and wasn't sure if I had just not put the cap back on fully, so I went on into work hoping it would be OK on the drive home.
I left work and started the drive home, only to have it start over heating again about 4 miles into the drive. I quickly pulled into a gas station and bought some coolant (I had the dex cool drained and the system flushed and replaced with regular coolant about 7 years ago) Before I added the coolant, I looked into the radiator and could see that the coolant looked full of bubbles, almost foamy. I topped off the coolant again and replaced the cap, and tried to start the engine. No dice. It turned over, but wouldn't start. I waited about 5 minutes and tried again. It started but ran really rough. So, I limped it over to a parking space from the gas pump I had parked next to. I shut it down and waited another 10 minutes or so for it to cool further. I got it to start and it was still running rough, but seemed to smooth out a bit after running for a couple of minutes. I started to drive again, but only made it a few miles before it started to get hot again. I pulled over again and let it cool.
When I started it again after cooling, it was still running very rough and threw and SES light. I kept the limping a few miles at a time till I made it almost home and stopped at an Autozone to have the codes read. They were P0125: Coolant Temp is always low and P0300: Cylinder misfire detected, random cylinders.
Afterwards, I made it home just as it was overheating again. Ok, I realize now that I probably should have just parked it and had it towed home or to a garage after it started running so rough, but honestly, I just wanted to get it (and me) home so that I could research the problem and hopefully find some solution. Now I am afraid that it is probably a head gasket or an intake gasket, and possibly something worse internally from driving that way now that those codes are coming up. I am really afraid that I may have trashed the motor. I have limited mechanical skill and the thought of tackling this is pretty intimidating, but I just can't stomach spending $1000+ right now, especially considering the car is probably not even worth that much. Argghhh!!
Anyone have any ideas about what I am possibly looking at here? Do I have any hope of saving this engine by changing gaskets and partially rebuilding the top of the engine? Am I going the screw it up more if I start it again to try to use a head gasket test kit? I am so confused and stressed about it, so any help would be great.

 

Being that the PCM is complaining about temp being low while the engine is overheating, you may want to take a good look at the ECT sensor (engine coolant temp), and its wiring. It is possible that the PCM is seeing low coolant temp and not turning on fans when needed. Otherwise, there is a possibility that a head gasket has blown. The random misfire may be due to the ignition stuff having gotten wet when the coolant blew out.

 

My guess (just a guess) is that you blew a head gasket and the pressure from the cylinder is getting into your coolant system. If a air pocket forms around a sensor and coolant can not reach the sensor it will read low temp.