2000 ford expedtion 5.7 how do i preasue test the coolant system to find a leak i think it is behind the manifold preasure tester kit i got from the auto parts store does not adapt to the resivor

The thermostat is in the housing where the upper radiator hose connects to the intake manifold.
Is the intake manifold what you are talking about ?

These motors are famous for the intake manifolds leaking coolant.Have a pressure test put on the coolant system and look for a leak around the intake manifold corners.Check all four corners i've fixed many of these.

You can buy or possibly rent a coolant system tester which pumps air into it to help locate leaks. Very simple to use. You just remove your radiator cap and replace it with the tester and pump it up to the PSI listed on your radiator cap and watch for leaks. I would pay close attention to the water pump and intake manifold gaskets. It could be something as simple as a loose radiator hose clamp. It is common for intake manifolds to leak and they expand when hot and contract when cool so the leak is more noticable after sitting. Look on top of the engine around your intake manifold and your heater hose for coolant or a chalky like residue which can form from coolant leaking. Your water pump has what is called a weep hole on it which will be located behind the pulley close to the shaft. You may need to use a mirror to see it. If coolant is leaking out of it the water pump will need replaced.

How about a crack in the cylinder head or a gasket leaking into either the inlet manifold and being sucked into the engine, or being blown into the exhaust system and being boiled away. Ask a radiator repair shop to carry out an O2 test on the coolant. They may detect presence of the gas in the water confirming a leak into the exhaust system.

Yes this could be a hose, a heaterhose, fill the cooling system and run the engine so that preasure build then before it gets hot shut it down and look for mhoses and squeeze them and try to locate coolant coming out , a preasure tester would be a great tool to find this leak but by you squeezing the hoses you should find the leak or even when the engine runs it may push water out, or sometimes when filling the system you can find the leak. hope this is helpful.

Does this vehicle have a 3.1 or 3.4L motor. If so they commonly have intake manifold gaskets failures. This leads to coolant leaking, usually at the corners of the intake manifold and in some instances leaking into the oil. Look for signs of coolant leaking at the corners of the intake manifold and check the engine oil for coolant.

could be that you have a leaky welsh plug have a look under the car where the transmission meets the engine and see if you can see white residue there is a welsh plug behind the flywheel which seems to give trouble on falcons also there are 5 behind the exhaust manifold which are hard to detect if they are leaking have had this problem with mine only has 80 000 on clock

Notorious problem with coolant leaking @ the intake manifold. Have the cooling system pressure tested to locate source.

is it overheating? this will cause it to preasurise excessively, causing loss of steam through the preasure cap.

otherwise if there is definately no leakage externaly when preasure tested, then it is probably leaking internaly. some cars now have EGR (exhaust gas recurculation) coolers, where coolant cools the exhaust gasses . This can leak, letting coolant into the exhaust system as steam. The only other passage for coolant leakage internally is through a leaking head gasket, or worse still a cracked cylinder head. check your oil on the dipstick, if it is creamy coloured then coolant is leaking into the oil. A headgasket/cracked head may also leak coolant straight into the combustion chamber, the only way to check this is to test for hydrocarbons in the cooling system (specialist test kit)

If the heater matrix is leaking, you would probably notice the front carpets getting damp. .

The heater core shares the same housing as the air conditioning evaporator core. The drain for the AC is designed to leak condensation. The coolant could be draining out of the same drain hole. To test a heater core you must use a cooling system pressure tester. If the pressure drops during testing search for your leak looking at all your cooling system components including your radiator. If the heater core is leaking coolant should be coming out of the AC drain hole.