Can't add coolant to a 94 lincoln mark 8

did you drive the car with no coolant in it

The 2006 LS must have the air bled out of the system every time the cap is removed to check or add coolant. There should be a rubber hose hanging somewhere very close to the plastic bottle where you add coolant. It will be capped off and the end will have what looks like a plastic screw. With a screwdriver slowly unscrew(open) until air starts escaping. After all the air is out and only coolant is leaking out retighten screw and you are done. Needs to be done every time you open the refill bottle as air gets in then.

The crossover tube under the alternator cracks there is a new style intake that uses a metal cross over

'coolant leak but hoses are fine'...? If it has a leak, where is it coming from?

your possibilities for overheating are varied on a Mark viii, things to check are the coolant fan-does it come on when you let it idle for a long period of time, NO air conditioning on? If not, your VLCM (variable load control module) is bad, it is located next to the suspension compressor, passenger side fender under the intake filter. Check fuses and relays too, you might luck out and find it is just electrical. That fan takes a lot of juice (60 amps!) so make sure your electrical system is in good shape-even the 130 amp alternator you have is barely marginal, I have a 200 amp in mine, it is a good thing. Water pumps on these are easy to replace, one of the easiest I have ever seen, so consider it. Also a Cobra pump is a better alternative to the stock pump.

there may be air in the system, these cars are prone to this and have to be filled properly after servicing the cooling system-the front of the car should be a little higher than the back, and after filling the surge tank, remove the cap to the crossover tube (1/4" drive rachett) and start the car, let it run and fill at the crossover tube until it dribbles out of the top-screw on the cap, drive it, and if necessary, check it after it has fully cooled down to see that it has no air in it. Your surge cap may be defective, and people HAVE installed the thermostat upsidedown, so you may have to double check that. And, id you have a leak, it needs to be fixed-the system should hold pressure when it reaches operating temp, you can check this by squeezing the top radiator hose, it should be impossible to collapse. there's always the possibility of a blown head gasket, but it would run badly, smoke out the exhaust, you'd find oil in the coolant or coolant in the oil-hope that is not the problem, these are a pain to do since it is a DOHC engine.

CHECK COOLANT LEVEL STILL LOW.ADD MORE COOLANT.UNTIL RADIATOR OVERFLOW FULL AT COLD MARK.THEN CRANK ENGINE UP LET IDLE FEW MINUTES LOOK DOWN COOLANT OVER FLOW JUG ADD MORE COOLANT IF LEVEL DROPPED.WHILE ENGINE RUNNING KEEP EYE ON TEMPERATURE GAUGE.WHEN THERMOSTAT HOSE GET HOT.TURN OFF ENGINE WAIT A LITTLE WHILE TO KEEP FROM GETTING SCALD TAKE LARGE RAG PLACE OVER OVERFLOW JUG RADIATOR CAP.OPEN CAP A LITTLE A TIME.IF COOLANT TRIES BOIL OUT.LET VECHICLE SET A WHILE LONGER.ADD MORE COOLANT.WHEN COOLANT LEVEL CORRECT AND ALL AIR OUT THE COOLANT SYSTEM.IT WILL STOP OVERHEATING.LONG AS ENGINE RUNNING HOT TURN OFF THE ENGINE POUR IN MORE COOLANT UNTIL COOLANT LEVEL STOP DROPPING IN RADIATOR.KEEP COOLANT LEVEL IN OVERFLOW AT COLD MARK.DONT OVER FILL OVERFLOW JUG.

Get your radiator flushed

When you top off the radiator you fill it to the neck where the cap goes. When the engine heats up the antifreeze eventually will distribute and the excess will go into the overflow bottle.

After the car cools, it will draw the antifreeze from the overflow tank into the radiator. Then check the level line on the overflow bottle(tank) for the normal amount of antifreeze per marks on the bottle.

You should have your radiator cap checked for its pressure rating. Use the type of cap which allows for an overflow system. The older caps would not let the antifreeze flow both ways.

Remove the P/S resevoir cap and add the correct fluid to the fill mark.

sounds like you may just have an air column in the system.Try this,Remove the radiator cap,start the car,turn heat on high,wait for the car to reach normal operating temp,and add coolant as needed.(if you watch inside the radiator,as soon as the car reaches operating temp,the water level will drop,That is the time to add more)

How is the problem with your mark? Has it been resolved? Is it physically overheating or does it just look like its hot? Have you swapped the sending unit for the coolant temp gauge?