Why does a coolant container with a loose hose that appears to have been welded off on one end, require that the thermostat housing unit be replaced.

To locate the thermostat follow the upper radiator hose to the point where it enters the engine. The thermostat is located below the coolant inlet that the hose is connected to.

To change it:

You're going to lose some coolant, so have a bucket or other container, and some fresh coolant ready. Follow the upper radiator hose to the point where it's connected to the engine. The hose is clamped to a metal housing (water inlet) which is bolted to the engine. Remove the bolts (not the hose) and lift the housing to expose the thermostat (may require a little prying with a screwdriver or similar tool). Note how the old thermostat is fitted (which end is up), lift it out of the engine, and then remove all traces of gasket from the housing and the engine. Install the new thermostat and gasket, replace the bolts, add coolant as necessary, and you're done.

Before you start the job though, check the condition of your upper and lower radiator hoses. If they show any signs of wear, fraying, or fatigue, you might as well replace them too.

BillB

You're going to lose some coolant, so have a bucket or other container, and some fresh coolant ready. Follow the upper radiator hose to the point where it's connected to the engine. The hose is clamped to a metal housing (water inlet) which is bolted to the engine. Remove the bolts (not the hose) and lift the housing to expose the thermostat (may require a little prying with a screwdriver or similar tool). Note how the old thermostat is fitted (which end is up), lift it out of the engine, and then remove all traces of gasket from the housing and the engine. Install the new thermostat and gasket, replace the bolts, add coolant as necessary, and you're done.

You're going to lose some coolant, so have a bucket or other container, and some fresh coolant ready. Follow the upper radiator hose to the point where it's connected to the engine. The hose is clamped to a metal housing (water inlet) which is bolted to the engine. Remove the bolts (not the hose) and lift the housing to expose the thermostat (may require a little prying with a screwdriver or similar tool). Note how the old thermostat is fitted (which end is up), lift it out of the engine, and then remove all traces of gasket from the housing and the engine. Install the new thermostat and gasket, replace the bolts, add coolant as necessary, and you're done.

You're going to lose some coolant, so have a bucket or other container ready. Follow the upper radiator hose to the point where it's connected to the engine. The hose is clamped to a metal housing which is bolted to the engine. Remove the bolts (not the hose) and lift the housing to expose the thermostat (may require a little prying with a screwdriver or similar tool). Note how the old thermostat is fitted (which end is up), lift it out of the engine, and then remove all traces of gasket from the housing and the engine. Install the new thermostat and gasket, replace the bolts, add coolant as necessary, and you're done.

You're going to lose some coolant, so have a bucket or other container ready. Follow the upper radiator hose to the point where it's connected to the engine. The hose is clamped to a metal housing which is bolted to the engine. Remove the bolts (not the hose) and lift the housing to expose the thermostat (may require a little prying with a screwdriver or similar tool). Note how the old thermostat is fitted (which end is up), lift it out of the engine, and then remove all traces of gasket from the housing and the engine. Install the new thermostat and gasket, replace the bolts, add coolant as necessary, and you're done.

You're going to lose some coolant, so have a bucket or other container ready. Follow the upper radiator hose to the point where it's connected to the engine. The hose is clamped to a metal housing which is bolted to the engine. Remove the bolts (not the hose) and lift the housing to expose the thermostat (may require a little prying with a screwdriver or similar tool). Note how the old thermostat is fitted (which end is up), lift it out of the engine, and then remove all traces of gasket from the housing and the engine. Install the new thermostat and gasket, replace the bolts, add coolant as necessary, and you're done.

You're going to lose some coolant, so have a bucket or other container ready. Follow the upper radiator hose to the point where it's connected to the engine. The hose is clamped to a metal housing which is bolted to the engine. Remove the bolts (not the hose) and lift the housing to expose the thermostat (may require a little prying with a screwdriver or similar tool). Note how the old thermostat is fitted (which end is up), lift it out of the engine, and then remove all traces of gasket from the housing and the engine. Install the new thermostat and gasket, replace the bolts, add coolant as necessary, and you're done.

You're going to lose some coolant, so have a bucket or other container ready. Follow the upper radiator hose to the point where it's connected to the engine. The hose is clamped to a metal housing which is bolted to the engine. Remove the bolts (not the hose) and lift the housing to expose the thermostat (may require a little prying with a screwdriver or similar tool). Note how the old thermostat is fitted (which end is up), lift it out of the engine, and then remove all traces of gasket from the housing and the engine. Install the new thermostat and gasket, replace the bolts, add coolant as necessary, and you're done.

Follow the lower radiator up to the engine. It's in the housing at the end of it.
If you're overheating/loosing coolant, you may have a leaking heater core.

You're going to lose some coolant, so have a bucket or other container ready. Follow the upper radiator hose to the point where it's connected to the engine. The hose is clamped to a metal housing which is bolted to the engine. Remove the bolts (not the hose) and lift the housing to expose the thermostat (may require a little prying with a screwdriver or similar tool). Note how the old thermostat is fitted (which end is up), lift it out of the engine, and then remove all traces of gasket from the housing and the engine. Install the new thermostat and gasket, replace the bolts, add coolant as necessary, and you're done.