I have no heat in my 1999 Lincoln Navigator. I replaced my thermostat and flushed radiator. I do notice that my antifreeze in the reserve seem to become dirty. The fluid seem to turn the antifreeze into a slite foam, as if it is backing up. The fans work, but just continue to get COLD air? What may be the issue?

Is your air locked slacken off top hose and make sure your getting a good flow of water no air

sounds like you need more antifreeze , make sure fluid is at proper line on overflow tank

COULD BE THERMOSTAT IF TOP RADIATOR HOSE IS NOT HOT AND BOTTOM RADIATOR HOSE GOING TO WATER PUMP IS HOT THE THERMOSTAT STICKING PARTIALLY CLOSE.IF TOP HOSE IS HOT THE RADIATOR,ENGINE BLOCK HEATER CORE NEED FLUSHING OUT.IF WATER PUMP WEEP HOLE LEAKING REPLACE WATER PUMP, FAULTY WATER PUMP WILL CAUSE ENGINE TO OVER HEAT.REPLACE RADIATOR CAP MAKE SURE YOU HAVE 50 / 50 MIX SOLUTION ANTIFREEZE AND WATER IN COOLANT SYSTEM. IF ALL LOOKS GOOD CHECK ENGINE OIL ON DIP STICK, IF OIL IN DIP STICK LOOK LIKE MILKSHAKE YOU HAVE BLOWED HEAD GASKET THAT WILL CAUSE ENGINE OVERHEATING WHILE DRIVING CAR IN SHORT DISTANCE AND ENGINE OVERHEATING.

do you have the proper amount of antifreeze in vehicle not over full if so your thermostat is bad

in your question while flushing it i had plenty hot air dont no reword what your asking please thermostat try replaceing that

1. Does your radiator fan works when the temperature indicator on H?
2. Have your flush clean whole cooling system and put fresh new coolant to resolve problem?
3. Does reserve tank amount ever decrease?
4. Have had the thermostat function checked?
5. Technically when you turn on the heater it bypass the thermostat line and goes into heater and after giving up heat enjoins radiator return line.
Happy hunting, cheers

Since your blower is working and it is a heat issue,thats where we'll start,First thing is have you checked the coolant level in the radiator when engine is cold,make sure it is filled to top,next verify you have coolant in reserve ,Start your van and get it up to normal operation temperature,If your heat gauge on the dash works correctly it should be 190 degrees,Now lift the hood and locate the two heater hoses going into the heater assembly at the fire wall,Both hoses should be hot to hold on to,if both are hot and no heat inside your problem will be the blend air door in heater assembly.
if neither hose is that hot you need to replace the thermostat in the engine to get it up to 195 degrees.
if one hose is hot and one is luke warm then the heater core is blocked and to blame. hope this helps you.

is there a thermostat for the heater loop the same as for the radiator loop on your car cooling system.

1 some cars have thermostats to keep the water just round the engine when the engine is cold and then they open as the engine gets warm to get the water cooled it seems that the water is not coming to the heating circuit so there maybe a thermostat valve that is stuck in the closed position and needs replacement
2 alterativly the heat control lever mechanism is stuck in the cold position and needs to be freed up or the control valve replaced.
3if the system is electrically controlled with no manual levers for heat control then a fuse may have blown or some other electical problem in the heat control mechanism.

if you use the orange antifreeze than id say you have a blown intake gasket or head gasket, combustion gases in your antifreeze makes it very acidic which probably ate a hole in your heater core and will probably eat your radiator soon if not fixed

Both the 4.0L and 4.7L engines use 195� thermostats for all model years from 1999-2004. When replacing a thermostat it is very important to install one with the same temperature rating (the only exception might be with certain performance modifications or chips that recommend or require a different temperature thermostat).

4.0L engine - Draining the cooling system WARNING: DO NOT REMOVE THE CYLINDER BLOCK DRAIN PLUGS OR LOOSEN THE RADIATOR DRAINCOCK WITH SYSTEM HOT AND UNDER PRESSURE. SERIOUS BURNS FROM COOLANT CAN OCCUR.

1. DO NOT remove radiator cap first. With engine cold, locate radiator draincock on the right lower side of radiator facing to rear of vehicle.
2. Attach one end of a hose to the draincock. Put the other end into a clean container. Open draincock and drain coolant from radiator. This will empty the coolant reserve/overflow tank. The coolant does not have to be removed from the tank unless the system is being refilled with a fresh mixture. When tank is empty, remove radiator cap and continue draining cooling system. To drain the engine block of coolant, remove the cylinder block drain plug, located on the side of cylinder block below the exhaust manifold.

4.0L engine - refilling the cooling system Coolant recommendations and cautions: The recommended mixture is 50/50 ethylene-glycol and low mineral content water. Never use pure antifreeze. Only Mopar Antifreeze Coolant, 5 Year/100,000 Mile Formula (glycol base coolant with corrosion inhibitors called HOAT) is recommended. This coolant offers the best engine cooling without corrosion when mixed with 50% distilled water. Antifreeze mixture must always be at least 44%, all climates year round. Maximum protection (-90d) is provided with a 68% mixture protection. If the percentage is lower than 44 percent, engine parts may be eroded by cavitation, and cooling system components may be severely damaged by corrosion. CAUTION: Mopar Antifreeze/Coolant, 5 Year/100,000 Mile Formula (MS-9769) may not be mixed with any other type of antifreeze. Mixing of coolants other than specified (non-HOAT or other HOAT), may result in engine damage that may not be covered under the new vehicle warranty, and decreased corrosion protection.

CAUTION: Do not use coolant additives that are claimed to improve engine cooling. 4.0L coolant capacity: 1999-2000: 13.0 qts. (including 2.3 qts. for resevoir) 2001-2004: 15.0 qts. (including 1 qt. for resevoir)

1. Tighten the radiator draincock and the cylinder block drain plug(s) (if removed).
2. Fill system using a 50/50 mixture of ethyleneglycol antifreeze and low mineral content water. Fill radiator to top and install radiator cap. Add sufficient coolant to the reserve/overflow tank to raise level to FULL mark.
3. With heater control unit in the HEAT position, operate engine with radiator cap in place.
4. After engine has reached normal operating temperature, shut engine off and allow it to cool. When engine is cooling down, coolant will be drawn into the radiator from the reserve/overflow tank.
5. Add coolant to reserve/overflow tank as necessary. Only add coolant to the reserve/overflow tank when the engine is cold. Coolant level in a warm engine will be higher due to thermal expansion. To purge the cooling system of all air, this heat up/cool down cycle (adding coolant to cold engine) must be performed three times. Add necessary coolant to raise tank level to the FULL mark after each cool down period.

For more details, you can refer to the Jeep WJ Service Manual Section-07-Cooling-System-Ewj7

Hope helped.