I have a 2003 Ford Expedition with 140,000 miles. It has cut off while in motion with no lights or messages. It has done this about 6 times. What could it be? I have had had fuel filter and spark plugs changed. Also, I have a coolant leak that cannot be found, I have to add about every 2 weeks and the truck feels like it has no power and idle's down almost shutting off at stops. It doesn't do it all the time but seems to be getting more frequent and sometimes I have white smoke coming out of my tail pipe it isn't all the time I would say twice in the last 2 weeks. HELP.

 

Pressure test the cooling system and compression test the cylinders.....

 

Sounds like you have a blown head gasket or a cracked head..........

 

Have you checked your oil to see if you have any coolant in it?