I have antifreeze leaking from somewhere in the front. I think it could be the thermostat housing. the leak only happens when the engine is warm and it's not that much of a leak. just enough to have to fill the reservoir once or twice a week,and it stinks of antifreeze when i park and exit the vehicle.

Clogged radiator, worn out water pump fins, oil pump failing, head gasket blown and leaking into the cylinders, thermostat stuck closed.

Break free 2 bolts on thermostat housing, loosen hose going into housing and clamp, it will leak some antifreeze. Once the housing is taken off block clean off old gasket material from both surfaces. The block and housing, be careful not to scratch the surfaces. No sharp pointy objects, aluminum is soft. Then take the old thermostat out and put in the new one. Put gasket in place ,align housing and put , bolts in by hand first, so it doesn't cross thread. Just snug bolts and top off system with antifreeze . Start engine ,put on heat and run until thermostat opens. Check for leaks, tighten bolts 1/4 turn should be fine. Add antifreeze in overflow bottle if needed.

follow your upper radiator hose from the radiator back to the engine. At that point remove the hose and replace it. Put it back together , fill up the antifreeze and you are ready to go.

what you do is go to a radiator specialist shop and have a coolant pressure test done
most probably a cracked top plastic tank
as for the leak at the back , it could be a rusty welsh plug but the pressure test will also show that

Check this diagram location...

Fig. Thermostat installation - 4.6L Engine

4.6L Engine

1. Drain the coolant to a level below the thermostat housing.
   
2. On some vehicles, access is easier if the front-end beauty panel and the air cleaner are removed.
   
3. Remove the 2 bolts securing the thermostat housing to the intake manifold.
   
4. Remove the thermostat housing.
   
5. Remove the thermostat and O-ring from the housing.

To install:

1. Install the thermostat and new O-ring to the housing.
   
2. Install the thermostat housing to the intake manifold. Tighten the thermostat housing bolts to 18 ft. lbs. (25 Nm).
   
3. Refill the cooling system using a 50/50 mixture of water and ethylene glycol antifreeze.
   
4. Install the air cleaner and beauty panel, if removed.
   
5. Start the engine and check for coolant leaks. Allow the engine to come to normal operating temperature. Recheck for coolant leaks.

Hope this helps.

Things You'll Need:

• Wrenches and sockets
• Torque wrench
• Thermostat and gasket
• Gasket scrapper
• Antifreeze
• Screwdriver

1. 1

   Follow the lower radiator hose to where it meets the thermostat housing. The thermostat housing is where the opposite end of the lower radiator hose mounts to the engine.
   

2. 2

   Drain enough coolant from radiator until it is below the thermostat. Failure to do this will result in your antifreeze leaking out onto the ground.
   

3. 3

   Loosen clamp and remove radiator hose from thermostat housing. Some antifreeze will leak out, so have some rags available.
   

4. 4

   Remove the bolts holding the thermostat housing on and pull the housing from the engine. The gasket might make it a little difficult, so do not be afraid to pull hard. Do not strike it with any tools as you can crack it.
   

5. 5

   Remove the old thermostat and note its alignment.
   

6. 6

   Place a rag in the thermostat's mounting hole so no gasket material can enter the engine and then scrape the gasket from the housing and the engine.
   

7. 7

   Install the new thermostat in same position as old one.
   

8. 8

   Reinstall the housing and tighten down bolts snugly. Torque them with your torque wrench to 10 ft.-lbs. Make sure you do not over-tighten them.
   

9. 9

   Reinstall the radiator hose to thermostat housing and tighten the clamp.
   

10. 10

    Refill the radiator with coolant and start the engine, allowing it to reach normal operating temperature.
    

11. 11

    Check for any leaks at hose connection and thermostat housing. You can tighten them as necessary to stop any leaks.
    

12. 12

    Stop the engine and allow it to cool down completely then check the coolant level. Add coolant as required.
    

Please choose the correct steps for the size of engine that you have:

4.5L & 4.9L Engines

1. Drain the coolant to a level below the thermostat housing.
   
2. It may be necessary to remove the upper air filter assembly on some models.
   
3. Remove the 2 bolts securing the upper thermostat housing to the lower housing.
   
4. Remove the upper thermostat housing.
   
5. Remove the thermostat and O-ring from the lower housing.
   

Thermostat installation—4.5L and 4.9L engines

To install:

1. Install the thermostat and a new O-ring to the lower housing.
   
2. Install the upper thermostat housing to the lower housing. Tighten the thermostat housing bolts to 20 ft. lbs. (27 Nm).
   
3. Refill the cooling system using a 50/50 mixture of water and ethylene glycol antifreeze.
   
4. Start the engine and check for coolant leaks. Allow the engine to come to normal operating temperature. Recheck for coolant leaks.
   

4.6L Engines

1. Drain the coolant to a level below the thermostat housing.
   
2. On some vehicles, access is easier if the front-end beauty panel and the air cleaner are removed.
   
3. Remove the 2 bolts securing the thermostat housing to the intake manifold.
   
4. Remove the thermostat housing.
   
5. Remove the thermostat and O-ring from the housing.
   

Thermostat installation—4.6L Engine



Loosen the upper radiator hose clamp at the thermostat housing



Remove the upper radiator hose clamp from the thermostat housing



Remove the thermostat housing retaining bolts and . . .






. . . remove the thermostat housing from the engine



Separate the thermostat from the housing

To install:

1. Install the thermostat and new O-ring to the housing.
   
2. Install the thermostat housing to the intake manifold. Tighten the thermostat housing bolts to 18 ft. lbs. (25 Nm).
   
3. Refill the cooling system using a 50/50 mixture of water and ethylene glycol antifreeze.
   
4. Install the air cleaner and beauty panel, if removed.
   
5. Start the engine and check for coolant leaks. Allow the engine to come to normal operating temperature. Recheck for coolant leaks.
   

It would either be the intake gasket, thermostat housing gasket,upper hose at the thermostat housing,or the heater hose that enters the intake.

It sounds like you may have a leaking head gasket or cracked head. I would suggest you do a compression test.

1. Drain the coolant to a level below the thermostat housing.
2. On some vehicles, access is easier if the front-end beauty panel and the air cleaner are removed.
3. Remove the 2 bolts securing the thermostat housing to the intake manifold.
4. Remove the thermostat housing.
5. Remove the thermostat and O-ring from the housing.

Thermostat installation—4.6L Engine Loosen the upper radiator hose clamp at the thermostat housing Remove the upper radiator hose clamp from the thermostat housing Remove the thermostat housing retaining bolts and . . . . . . remove the thermostat housing from the engine Separate the thermostat from the housing To install:

1. Install the thermostat and new O-ring to the housing.
2. Install the thermostat housing to the intake manifold. Tighten the thermostat housing bolts to 18 ft. lbs. (25 Nm).
3. Refill the cooling system using a 50/50 mixture of water and ethylene glycol antifreeze.
4. Install the air cleaner and beauty panel, if removed.
5. Start the engine and check for coolant leaks. Allow the engine to come to normal operating temperature. Recheck for coolant leaks.