oil sludge?

I have a 2002 4x4 Durango with the 4.7 L V-8. I have 60,000 miles on it and have had this vehicle since it was brand new. I had the vehicle heat up and I replaced the thermostat and added a small amount of coolant that was lost doing this. I pulled off the oil fill cap and found a thick brown substance with water on top off it. so much that I don't think oil could be added. I tried my best to clean it out with 20 Q-tips. I have always had my oil changed at 3,000 miles and went to Mobil 1 last year and run that about 5,000 miles. My coolant was not low and I do not loose engine coolant. When I check the oil level with the dip stick it is at the correct mark and looks like it is almost new, with no foam or water in it. I changed my oil 1/30/2009 and nothing looked out of order about it. I did at that time have a hard time putting oil in. It took a long time to pour the oil in. I cleaned the oil fill tub out then with Q-tips as well. Is this a head gasket problem or because it overheated and the filler tub is high up from the motor and condensates. Any ideas?

Check the PCV system, poor circulation causes this to happen. When the engine cools, condensation forms inside the engine and turns the oil into a milkshake-like gooo. The PCV system keeps the crankcase ventillated so condensation can not build up.

With the engine off, pull the PCV valve out of the rocker arm cover and shake it, it should rattle very freely. If not, replace it.

On the oposite rocker arm cover is hose, that hose is the intake for the PCV system. With the engine running, there should be a slight vacuum at the hole in the rocker arm cover where the hose attaches. If no vacuum is present, pull the PCV valve out and put your thumb over the valve inlet, there should be a strong vacuum. If not, follow the hose to the intake manifold and check it there. When you find and fix the problem, the rocker arm covers should be removed and cleaned out, they'll be full of that same milkshake gooo.