My car is over heating when i shut it off the coolant resivoir is boiling and brown in color

check fan operation
if viscous fan hub --replace the hub
if electric fans , check coolant temp sensor , 2 fuses , fan relay and fans
When an engine is shut down , the coolant temp will rise as the heat is still in the cylinder walls and heads and the water is not being circulated
when it goes to instat boil , the engine temp is close to boil anyway

bubbling noise is the radiator boiling. If you have a viscous fan hub the have it replaced as the engine is getting too hot. When you stop an engine thee is still heat being transferred from the combustion chambers into the coolant. When the engine temp is close to boiling , this heat will cause the coolant to boil when you shut the engine down

If the fan is working ok there are still a number of things that will cause your vehicle to run hot and have the fluid from the radiator boil over into the resivior. It is possible that the thermostat is not opening up and allowing the coolant to flow through the motor and radiator properly or that the water pump is not working properly also causing the same issue either due to a missing belt or warn out bearings that have locked up. It is really impossible to tell you exactly what the problem is with so little information but those are the first two things that I would check out.

If you have eliminated as a cause:-

- silted up radiator
- fans not running (if they are running the temp sender is OK)
- leaky head gasket putting gasses into the water jacket
- radiator hose going soft and closing up

then that leaves the thermostat being stuck closed. Also if the coolant is disappearing this may still be a hidden leak. The V6 has a joint under the inlet manifold which is prone to leaking coolant, and on a hot motor the water disappears quickly.

First of all, don't "disable" the thermostat, It is an important part of the cooling system. Without it, you could crack the cylinder head from coolant boil-over! Ok, the most obvious sign of a cracked/warped head, or gasket failure is white smoke at the tail pipe, air bubbles in the cooling resivoir, milky, thick, coffee with cream colored oil, or external coolant leaks. If you just have an overheating problem, you should investigate the cooling system first. Check the fan(s), there may be a belt driven and an electric fan for your truck, make sure they both are operating. (turn the ac on with the engine warmed up) Check that when at operating temperature, shut the engine off and make sure the belt driven fan has resistance when you turn it by hand. If it turns and spins freely, replace it. Flush your radiator with a good coolant flush chemical and follow the directions. When flushing, look for water flow in the radiator cap. Replace that thermostat with a new one! replace the coolant cap also. Check for debris on the radiator fins like leaves, plastic bags, mud and bugs.

A flush and a thermostat is never a bad idea, but it sound like your radiator cap is worn out, not holding pressure, replace it, should have a 16 lbs rating radiator cap.

I assume the coolant is not actually boiling and that the coolant is bubbling even when the engine is relatively cold. If so this would indicate a blown head gasket. Exhaust gases are escaping from a cylinder into the coolant passageways at the head gasket junction

Keep in mind that there are some things you wouldn't want to substitute on your car when it comes to fluids and maintenance but you should be safe to use an aftermarket anti-freeze. Most anti-freeze is a form of alcohol since the boiling and freezing points of alcohol is much higher and lower than plain tap water.

Hi,
A common problem with overheating that get's overlooked, is a sticking thermostat. As inexpensive as it is, and as easy as it is to replace, I would strongly suggest replacing it. An overheated engine could be catastrophic and a huge expense. I hope your problem is resolved...