ok. no just changed the oil today, looked normal

 

ok. no, i just changed my oil today, it looked normal

 

It still may not hurt to flush the system with an additive to assist in removing scale and sludge from the cooling system.
That mud-like substance is probably all around the cooling system and it's passage-ways. Using an additive made to assist in flushing the system should help break that stuff apart to get it out.

I also agree with a leak test using a radiator pressure tester. Hopefully if you can get a hold of one, the results will come back with no leak.

 

What year and engine do you have?
We have a 2001 3.4 and the same thing began to happen and I figured a blown head gasket as it appeared oily. Finally noticed a little leak at the manifold gasket.
Read here on this great forum and found manifold gasket leaks are very common on the 3.4. No cash or time to repair properly so did the evil deed and used radiator stop leak goop and immediately stopped the leak and the muddy coolant. Soon after flushed several times over and all has been well the last 15,000 miles.
Good Luck