Cracked Block? Head? Headgasket?

Hi, My Toyota Tacoma's coolant froze, and I am trying to determine what has happened to my engine (2.4 2RZFE). In the cold my truck would not turn over. I put a space heater under it for about four or five hours, and tried again. This time it ran for about five minutes before dying. I have heard about the cold cracking engine blocks, so that was my first suspicion. I checked my oil and it looked like milk.

I have two theories about what might have gone wrong:

1: I cracked my block with the temp change

2: My hoses might not have been completely thawed and I may have blown my head gasket. The truck will not run right now.

How do I determine which has happened? If the block is bad I will be in for a new engine, but if it is only the head, then I will just fix that. I just don't know how to test? What else could have gone wrong? Thanks

Oil that looks like milk is a sign that coolant has mixed with the engine oil. This can happen from a head gasket leak, a cracked head, or a cracked block. If the coolant was allowed to freeze, any or all of the above could be the result.

First, determine why the engine will not run. If the engine turns over, then check for the basics - air, fuel, and a source of ignition.

The way to check is to pull the head, examine the head gasket for signs of leaks, and send the head to a shop to be checked for cracks. If the head and the head gasket are OK, then start shopping for a new engine. If the head gasket and/or head do show signs of leaks, you may still need a new engine.

You have probably learned your lesson, but just in case, always check the condition of the coolant and do not use straight water in the cooling system.