Spontaneous Max Overheat during Idle in Hot Nebraska Parking Lot
I have asked another board but just wanted to ask you guys to, so forgive me, if you follow both.
I am already freaked out that this is a cracked cylinder head but let me just post what happened. I am driving through Nebraska and got a call so instead of staying in the restaurant and taking the call, I jumped into the car and idled and had the AC running for 20 minutes in the noonday heat. I noticed the AC was off and just the blower/fan and then noticed the temp was not in the middle, like always, but in the red, with the light on. All the way in the red. Instead of turning the car off, I started driving to get some air in it and it got worse, so I stopped the car, opened the hood, and there was coolant all over the inside of the hood/bonnet. The temp gauge went all the way to hot and turned off, actually. And stayed all the way right. I had a rural mechanic come over and look at it and it had cooled but there was no coolant in the reservoir. I drove 1/2 mile to the garage and their first diagnosis is a crack in the Radiator Coolant Overflow Tank, which I will replace, so they can do the test to see if it is, in fact, just that crack or if the pressure backup from a cracked cylinder head. What is your intuition. I know that I should not have been idling in 100F heat in the car with the AC on -- and I also know that I should have turned the car OFF when I saw the overheat and left it there for at least 1/2 hour. But I didn't. But I will do from now on. What does your intuition say? Replace the Radiator Coolant Overflow Tank or the whole engine?