2008 F-150 4X4 XTR. Can't figure this one out. Drove 7 hours pulling a 28' trailer at about 65MPH or 110KPH and when I checked my fluid the next day before moving on, the coolant was at the bottom of the jug. I paniced right away. I looked under the truck and nothing leaking. I ran it and smelled the exhaust and no coolant smell. I got a jug of yellow coolant from the ford dealer ($32) and put a whole jug in to get it back to the full mark. Drove 2 hours at 55MPH or 90KPH and it stayed at the full. Still no leaking or coolant smell in the exhaust. Next day drove 7 hours back home and the same thing. Stayed at the full mark. For the last week I drove 200 miles or 320km and still at the full mark. What the hell happened. Could it be that when driving 65MPH there is enough temp gain that the head gasket lets some coolant thru? Could there have been an air pockets somewhere in the block that passed thru? I have no idea. Never heard of this before. Your thoughts would be appreciated...

 

did the engine run a little hotter than normal while driving at that speed?

 

No it did not run hot at all.
The temp gauge always stays straight up at half.

 

It's always better to mix the concentrated coolant with water to obtain a 50-50 mixture.
Sometimes things happen that defy answers and the coolant disappearance could be one of them. If everything checks out OK , just keep an eye on the coolant level for a few weeks . If there is a potential problem developing you will at least be on top of it because you are watching the coolant level closely.

 

Thanks for the responses.
I will monitor the level.
ps. I did mix the coolant 50-50. But Thanks.

 

Paul... did you check the oil.. just to be safe....

 

I checked the exhaust fumes and NO coolant smell.
2 weeks later I did an oil change. The exact amount came out that I put in. Maybe a cup less. Looked golden yet and no smell of coolant. Looked normal.
It is a mistery.

 

I have A 1998 f150 with a 4.6 and it has been using alot of coolant about a gallon a month. I find no signs of it in the oil. I think I have A bad head gasket or intake gasket but would like to confirm this before i decide to tear it apart. so your not the only one with a truck using coolant.

 

Yep... sounds like an exhaust leak... At least not a head gasket leak!

 

if the reservoir has nothing in it maybe it,s the radiator cap not releasing the pressure ! check the oil to be sure there,s no antifreeze in it ! if there is then you have a head or intake gasket leaking !