Anyone have this problem in the 4.6? the car is using coolant, nothing on the ground. Thanks

 

With nothing on the ground, I'd check to see if there's water in the oil (would be grey) or if there is excessive white smoke coming out the tailpipe. Either of those cases would indicate either failed/failing head gasket, cracked head or cracked block. Another problem could be if temps are overheating and the radiator is boiling over while driving and by the time you stop there isn't enough coolant for any to overflow... this would probably be a thermostat issue, but could also have to do with the earlier issues. Either way it should be looked into as it won't be getting better on it's own, and could leave you stranded.

 

Thanks, for your response, no water in oil, no steam from tailpipe, no overheating. I just purchased the car, the expansion tank was down about 3" from the cold fill mark when I got the car home, I was hoping it was just underserviced. I filled it to the correct level when it was cool, it dropped about 1/2" the first drive after filling. I read that you should have the filler cap pressure checked, and then the system pressure checked. What do you think from above? Thanks again...

 

Okay, you only filled it once? There are some spots in the systems, mainly the crossover pipe that just filling will not get to and they recommend a special tool to get the water to that portion, but I believe driving gets it there. At this point, try topping it to the fill line and see what happens as you drive it around, if it still goes down. One other possibility is a slow leak from the hoses into the engine valley, this would evaporate quickly and not necessarily pool up under the car, this would look like whitish powder in the engine valley under teh intake manifold (tough area to get a good look at). A pressure test of the coolant system should show if there are any leaks.
But I'd start first with topping it up and watching the levels, and compare at similar coolant temps like before starting it up in the morning.

 

Thanks for the advice, I will try the top off first...

 

The top off looks like it worked, I will keep an eye on it. Thanks for your advice....