Overheating and now not starting

[leonvr]

I have a Jeep Grand Cherokee Ltd 4.0L 2001 model.
We drove up into the mountains to stay at a resort for a few days, where there were sub-zero temperatures.
Now the Jeep was perfect getting there, but on leaving, it started overheating, going into the red, the water was boiling, and I had to stop a few times for it to cool down.
I managed to get back home allright after a really rough descent down the rocky roads of the mountain and then back onto the freeway, where it seemed to stay coolish all the way - hotter than normal - between half and three quarters way up the temperature gauge - where normally it rides at about one third way up.
Once ariving home and letting the car cool down a bit, I decided to check the cooling system and found that it hadn't used much water at all - i pressed the pipes and ran with the cap off to make sure there were no air-locks, and all seemed fairly normal. I did add some coolant anti-freeze/anti-boil additive to the system.
I took the car on a drive for about 3 miles after that, and suddenly it stopped - i could not get it restarted after that. It cranks, and seems to have spark, but won't start - the same sort of conditions you would have when it's not pulling in gas.
My first thought was that the head gasket had blown from the overheating. But on checking the oil colour, it appears to be allright - normal oil colour - or even perhaps a bit darker than normal. Coolant water colour seems to be fine too. With the cap open I am able the press the top pipe and the bottom pipe ok - bottom pipe is stiff, as it seems to have an anti-collapse spring in it.
I checked the fuses and relays - all seemed fine. I checked the wiring loom and connectors all around, and especially the connector to the crankshaft position sensor, as I thought there was a possibilty that could cause it not to start. Still no go. Help??!!

[GTP Dad]

Welcome to AF!!

The first place to start is with the basics. Make sure you have fuel and spark. Without either the vehicle will not start. I don't like doing it but try spraying some starting fluid into the throttle body while cranking the car. If it starts you have a fuel issue and you may need to replace the fuel pump. If not the next place is to check spark, I don't know that much about the location of the ignition module on the Jeep but it is possible that the extreme heat may have fried it and it will need replaced.

Since the car overheated I would pull all the plugs and do a compression check on the engine. Just because there is no water in the oil doesn't mean that the head gasket did not blow. This is a cast iron engine and it doesn't have the same issues as an engine with aluminum heads when it has overheated but the gasket could have gone just the same. Also if the engine got as hot as you indicated there may be an issue with the valves. If they are stuck open there would be no compression as well.

I have a question about your coolant. You stated that you were in sub-zero conditions, I am assuming that is Celsius given the fact that it is July. What is the strength of you coolant. Is is pure water or do you have antifreeze mixed in. If the coolant is water there is a possibility of freeze up. If you have a 50/50 mix then I would suspect the thermostat being stuck in the closed position regardless I would replace it just in case once you get the vehicle started.

[leonvr]

Thanks GTP Dad
Good solid advice there.

After trying all as you suggested, I suspect I may have cooked a valve.
I will have to open it up tomorrow

Will post back once I have found exactly what went...