Not a truck but I have a 92 Grand Marquis with a 95 engine. Car only has 78,000 miles on the engine and has never been hot. The needle has never moved past the R on NORMAL and usually sits on the N. Just replaced the thermostat and the guage has the exact same readings, so I believe it is accuarate. Two places heard the symptons - white smoke and a plume of white smoke when you gun it and both said its a head gasket. BUT, the coolant level is exactly where its supposed to be, oil looks good and the engine runs perfect except the mileage seems to have dropped off a little (from 25 to 21). Neither place seemed like they where going to test enything but just start tearing into the engine (expected costs around $1000+).

Is there anything else that could be causing the problem? I parked the car with the nose up hill and let it idle after driving it 30+ miles. After 10 minutes of this water started to trickle out the exhaust pipe and left a puddle. I know if it is taking that much water from the coolant system it would have been dry a long time ago. Could it be condensing(?) that much water just through normal driving? The white smoke smells(!) like exhaust - not sweet like coolant vapor

 

If the weather is cool it will. The cat's help turn the exhaust into water and in the cold weather, it will condensate alot. If there was no anti-freeze in the water puddle, then I wouldn't worry too much about it. These cars have a long exhaust system with many places for water to build up when the pipes cool off after running, so it will put out alot of condensate.
Jimmy

 

Thanks for the reply