My truck sprung a leak somewhere near the back of the motor. I was driving for 45 mins or so and when I got home, I put the truck in the garage and when I turned it off, rad fluid spewed out from somewhere near the back of the motor by the firewall.

I looked in my Haynes book and the only thing that I could think of being the culprit would be one of the lines going into the cab for the heater core. I couldnt really see it from all of the steam.

So, now I have replace one of these blown lines, but I guess flushing the core to see where the block it. The temperature guage never went above 1/2 level.

Is it possible to have a plugged core to make one of these lines burst, or was it just one of these line giving away to age that could have caused this?