After 376K faithful miles, the 6.5L in my Tahoe has finally had a major issue. Without any warning, she started blowing a lot of sweet-smelling steam out the tailpipe, and coolant is getting in the cylinder(s) causing it to hyrdolock after shutting it off.

Everything was perfectly normal this evening, and then I stopped for fuel. Upon filling up and attempting to restart the engine, the starter cranked her over for a second and then stopped cranking. I thought it was odd, but figured it was just the starter getting old. I cranked her again, and this time the engine started, but started knocking loudly for a few seconds. That was really odd. She started running normally, so I pulled away from the fuel pumps, looked in my mirror, and saw a huge cloud of smoke. I pulled over and got out, but by the time I got to the tailpipe, it had cleared up. I drove on home (about 4 miles), and then she was smoking again; actually, it was steam. I shut her down, checked a few items, didn't notice anything out of the ordinary, and then cranked her up again. Once again, the starter stopped cranking after a second while making a weird noise. That's when I realized something was preventing the engine from turning over. I tried again, she started up, started shaking and missing, and blowing a LOT more steam!

Here's a video right after I got home:

https://www.youtube.com/watch?v=ExXS6BNtEVM

After this video was taken, it started running horribly and smoking/steaming a lot more. In fact, by the time I drove it over to my shop a hundred yards away, I was wondering if it was going to stay running.

It takes less than a minute after shutting down the engine for the cylinder(s) to get enough coolant in there to hydrolock the engine.

My plan is to pull the glow plugs and then turn the engine over. That should pinpoint which cylinder(s) are getting coolant in them.

What do you think? Blown head gasket? Cracked head? Cracked block? At this moment, there is no coolant in the oil. I released the pressure on the coolant tank, but haven't been able to run the engine to see if there was any noticeable exhaust in the cooling system.

*sigh*

Casey