Originally Posted by eruji
Whats the best way to verify the leaking head gasket or cracked head?
You've got some options
First warm it up real good, shut it off and check the oil cap and dipstick looking for muddy looking oil, it should be pretty obviously brownish green if it's leaking bad. However you may have a blown gasket and not have these symptoms
If nothing then start pulling spark plugs looking for coolant on them
I've heard some people test it with all plugs out except one, pull off the radiator cap as well and crank the engine, if you see bubbles the gasket is blown (I can't verify this method).
Some people will do compression tests or leakdown tests, but those can easily miss a blown head gasket
The best test (other than seeing obvious signs of coolant in the oil) is to use a chemical test kit, you should be able to find one doing a google search for head gasket test kit. It has a test tube sort of thing that sits on the radiator in the fill spout, and has a color changing fluid that lets you know if engine gasses are entering the coolant.