Coolant is pouring out rear of the engine in my 2000 ford excursion v10. Engine didnt over heat. reservoir tank had small leak, I replaced the tank & cap but still coolant pouring out rear of engine

run fault codes
indicate ambient temp sensor , maf,vaf or engine coolant temp sensor problems

Sounds like the engine is being severely overheated and shuts down. I suggest you seek a shop out right away and find out how much damage you have done, you may have bought yourself a $10,000 engine job.

Does it get hot mainly when parked or stopped at a red light or does it get hot even when the car is in motion?If its only when your stopped,the cooling fans are probably not working due to a blown fuse,relay or bad fan motor.If the coolant inside the reservoir seems to boil once the engine gets hot,that can be caused by a defective radiator cap.A blown head gasket will also cause overheating.If you let the engine idle for a few minutes,shut it off,pull all of the spark plugs,see if any plug or two adjacent plugs are wet with coolant, that's a sign of a blown head gasket.If you constantly need to refill the radiator with coolant, that's another sign.

Probably has dirt in it. Use compressed air and blow it clean.

Begin with the basics....
INSPECT COOLANT LEVEL,
Low ????,PRESSURE TEST SYSTEM,
PRESSURE TEST RADIATOR/EXPANSION TANK CAP,
INSPECT DRIVE BELT(s),
INSPECT COOLANT HOSES,
INSPECT HEATER HOSES,
INSPECT BYPASS/MISC. COOLANT HOSES/PIPES,
TEST THERMOSTAT OPERATION,
INSPECT RADIATOR COOLING FAN(s)/CLUTCH OPERATION,
INSPECT CONDENSER/AUXILARY COOLING FAN(s) OPERATION(s)
INSPECT RADIATOR & CONDENSER FOR DEBRI,
OBSERVE COOLANT TEMPERATURE GAUGE OPERATION,

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check to see if rocker arm is broken on those cycl this is a common problem with v10 pull valve cover youll see it

Does it have a rear a/c. If it does u Broken the heater core in the rear of the truck. Needs to be repaired and filled with coolant before driving or u can cause damage to engine

Fuel pressure for your 2000 Excursion is 35-45psi with key on and engine off, with engine running the fuel pressure should be 28-45psi

replace the radiator cap and or the hose to the coolant reservoir. If there is a leak in the coolant tank to radiator hose then vacuum can not be created to draw the coolant back into the engine as it cools. A cracked, pinched or loose hose would be suspect. Or your radiator cap is not allowing the coolant to flow back into the engine; there is a small valve in the radiator cap for this purpose. This is assuming the engine is otherwise operating correctly; ie no blown head gasket.

You may have a blown head gasket. One of the head gasket's job is to prevent coolant and oil from entering specific parts of the engine. Over time the gasket wears down and holes appear. Your cooland may have passed through these holes causing it to mix with oil. You would notice steam appear at the tail pipe, where some of the coolant may mix with the exhaust as a result of this.