My 1999 ford taurus heater doesnt work. We recently had a problem with the reservoir boiling over and brown coolant. Had the thermostat replaced and replaced the radiator cap. Also flushed the radiator. The a/c works and the fan works when I turn the heater on...just blows cold air instead of warm. What can I do to fix it?

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.

Are you sure you burped the air out of the cooling system after making those repairs?

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remove the wire to the temperature sender unit and earth it out on the head. Turn on the ignition and see if the gauge goes to hot quickly. If it does then the problem will be in the sender unit so replace it. They are a resistance material inside that has high resistance when cold and the resistance becomes less as the water heats up so letting more current flow through the gauge so it goes up. They are prone to failure in an overheat situation. From your description the sender unit has failed inside

unless it is the heater core which you should flush system,,i always boil my new thermostat to make sur it compresses

It sounds like you have an air pocket in your system. By the RH strut tower take the heater hose loose from the metal line and fill the cooling system when coolant starts coming out reconnect the hose. If that doesn't work jack the car up where the over flow tank is the highest point and fill the cooling system.

have you recently replaced your waterpump ?

Try checking the two pipes that go into and come out of the heater matrix, is one of them hot? if it is there is an air lock within the matrix, Also is the thermostat opening fully? Sorry i know you said you have changed it twice already but take it out check settings when it should open and close, then boil some water and test the thermostat

it sounds as if you need to replace your thermostat

Ford 2000 Taurus

To solve the problem you have the things to do in this order;

) When the engine is cold top off the radiator with fluid. (When the pump was replaced the fluid should have been also)
) Make sure the radiator fluid has anti-freeze in it. This is also anti boil also !
) Add fluid to the overflow reservoir.
) Make sure the drive belt was replaced on the water pump.
) With the engine running, you can add fluid to the radiator for the first minute or so. You want to get air pockets out.
) Replace radiator cap.
) Let car warm up. When it's hot you should get the radiator fan coming on.
) When it get hotter the air-conditioning fan may come on.
) If the fan does not come on, the heat sensor is probably bad.
) If all fans come on, and it overheats, you may have a bad thermostat. Trace the upper radiator hose to where it connects to the engine. That's where it located.

Do not operate the engine when it overheats, You will damage the head gaskets and cause radiator fluid to leak into the cylinders.
If you smell radiator fluid in the exhaust fumes, it may already be leaking.

Hi!
Sounds like your Heater Matrix/Core is weeping, the brown stuff is possibly a leak sealer which someone before used to stop it.
You could try some more? remember to bleed the coolant as an air lock is possibly causing your overheating.
Park on level, when cold remove cap, start leave to idle when hot it should bubble over, top up with very warm water, wait it may do it again.
When happy pop in your leak sealer and hopefully your sorted.
Good luck! and please remember to rate my effort.
Paul 'W'
Onyer~EDson(:0) {#><U.K.