2003 lincoln ls losing coolant don't see leak now it is running hot it is cold here. Not sure if fan is working

Good chance it is.

There is an Auxilary Coolant Pump, you can
check out, below the coolant control valve,
against the radiator near the bottom, on passenger side

Wouldn't a repair shop have figured out the problem ?

Hello
Based on what you have said and my 30 years a Ford dealer tech I believe you have a slightly low AC system refrigerant charge due to a small leak at the AC compressor or the AC line connections. I would have a shop hook up a set of gauges to monitor the pressures at idle and see just how low it is. DO NOT ADD UNTIL YOU KNOW HOW MUCH IS NEEDED, YOU CAN LOCK UP THE COMPRESSOR.

Sound like a coolant (antifreeze) leak. This leak could be anywhere, including the heater core which could be expensive to fix. Check the coolant level when the engine is cold to see if it is low. Don't drive with missing coolant as you may destroy your engine.

do u hav the rite thermostat or is it in correct--shud be closed at startup-if not takes long time to get at operating temp and bad gas milage too

Yes we had a Saturn which we thought was running hot and the gauge was always in the centre or over but we had the fan checked and it was working. Our thermostat might of been faulty but we never had a overheating issue..My Mechanic said that we should get a coolant flush that might help.

you need to verify and fill the coolant in the radiator and reserve when the engine is cold,also check to make sure your cooling fans are kicking on when it is hot

When the car is completely cool,check the electric fan(s) for smooth rotation.

Clean/check/change the thermo sensor,contact and wire.

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Excavate air pocket in coolant system / check for head gasket leak

This test will kill two birds with one stone.

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MAKE SURE THE COOLANT SYSTEM and ENGINE IS COLD!

RAN THIS TEST IN A WELL VENTILATED AREA ONLY!

You will spill some coolant during this air pocket purge test.......BE KIND TO THE ENVIRONMENT and ANIMAL please clean up after the test!

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Put the front end on a pair of ramp or park your car on a VERY STEEP HILL (radiator facing top of the hill) .

Top of the coolant reserve tank

Let it ran for 10-15 minutes.

Monitor for air pockets escaping from coolant reserve tank.

Small amount of bubbles is OK at 1-5 minute mark

After the thermostat open up (after 195 F warm up) at
5-12 minute mark or after high idle you should see less bubbles.

If you do not see any in rush of bubbles then your thermostat may be partially stuck or rusted badly inside the thermostat hosing.

Give the thermostat host few gentle taps.

If you see larger bubbles surfacing after 15 minutes then should do a hydrocarbon (HC) dye test to test for potential head gasket leak.

Let engine cold down and top off coolant reserve tank.

Start monitor for coolant lost

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A coolant flush is require every 2 years or 24,000 miles.

I recommend the thermostat that has a relief pop-let to reduce the change of burst radiator and coolant hoses.

Make sure you get a new thermostat gasket,black RTV and fresh coolant for the job.

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Check to see if your radiator is holding pressure. Fell your radiator, let it idol and make sure nothing is leaking. If you have a small leak, try running through a bottle of MAC's(or any brand) leak stopper. It should work. But make sure you follow all the instructions, when it says let it idol for 30 minutes, let it idol for 30 minutes. I have seen/found Lincoln LS's seem to have quite a few leaks that pop up on it's radiator, the plastic thermostat housing and it's cap. Have fun.

replace the air filter and then hit your status button when it gets to ac filter press and hold reset until you see life go to 100 percent as far as the overheating YOU MUST BLEED THE COOLANT SYSTEM i had this same problem and it took me like six months to figure it out so i know your frustration you can find full instructions on how to do this at lincolnvscaddilac.com aswell as many other tips and people who know what they are doing with these cars who can help