You need at the very least a coolant backflush, switch to green coolant and a new radiator cap. However you stated that you are loosing coolant, you could have a crack in black plastic radiator side tanks, but since you said your coolant is nasty and you have a leak, it sounds like your intake manifold gaskets are leaking and that's a big $ repair and will result in engine damage if you don't repair it.
A crack in a side tank would result in the truck heating up rather quickly, as there would be a severe loss in pressure. If it's a hose, the leak is most likely only going to be apparent when there is LOTS of pressure, i.e.: when it's already warm. And on the intake manifold gasket comment... You're an idiot. The intake manifold gasket makes not contact with ANY fluid. The only gasket that could cause a coolant leak AND mix fluids is the head gasket. Otherwise, if it is a gasket, then it's a cooling system gasket or seal. And intake manifold gasket are NOT a pricey repair, and they hardly ever go bad, unless they're re-torqued repeatedly. In the event that it is a head gasket, it's ALREADY a big repair bill, the motor will hydrolock sooner or later, because there is coolant seeping in the cylinders... and coolant doesn't compress. (Bent rod, cracked piston, blown rings, warped/cracked head, or any combination of those things will result, just to name a few).
You might also check to see if the car has a fail-safe thermostat. If it does not, it can fail and lock into the closed position, creating tremendous back pressure on the open loop section of the cooling system. That results in cracked hoses or other leaks. If it is a fail-safe, then the vehicle would take quite some time to get warm, and the entire cooling system would be open, making it difficult for the system to heat up.
on the bottom of your water pump is a wheep hole you could be loosin coolant from their check all your hoses and clamps if its a head gasket sell that chit to a dumb sob lol you will know if its a head she will smoke like a train
Jeez... Read your post. Again. Now think about the qualifications required to call someone a "dumb sob". I'm ashamed that you're from Texas. A blown head gasket does not always smoke. Smoke is created by oil getting into the cylinders, steam is from the water in the coolant burning off. Most of the time, with coolant in the cylinder, you will get a stream of coolant at the exhaust tip. Also, the color of the smoke can tell you a lot. White/Blue smoke is not smoke. It's steam. It's from water. Darker colored smoke is usually from oil. But again... A blown head gasket DOES NOT always smoke.
This place is the blind leading the ****ing blind.