White Smoke after Long Steep Hill

I have a 2003 Ford Explorer with around 93,000 miles on it. I got the oil changed just before going on a long trip. It had been about 4,000 miles since the last oil change. My trip was about 3.5 hours in each direction with mostly highway driving where I was cruising at around 65-70 MPH but some long steep hills mixed in as well. On the way to my destination after cresting over one of these long steep hills, and going about 60 MPH while heading up the hill, white smoke started billowing out of the exhaust every time I hit the gas pedal. I pulled over and white smoke was creeping off the muffler as well. I’m not very mechanically inclined, but opened up the hood anyways, and thankfully no smoke or anything in there. I let the car sit for about 5 minutes until the smoke stopped creeping off the muffler then drove the rest of the 30 minutes or so to my destination with no more problems.

On the return trip, the same thing happened (different hill) with about the same timeline. I was about 30 minutes out from home, had just crested over a long steep hill going around 60 MPH and the white smoke started coming out again every time I hit the gas. Pulled over again, waited for the smoke to dissipate and for no more to be coming off the muffler and finished my drive home with no problems.

I’ve only owned the car for about 6 months. I haven’t encountered anything like this up to this point. And in the month or so driving it since the trip and incident, I have not seen any white smoke .

There are no warning lights on, the temperature gauge looks completely normal. From what I have read online it seems like coolant would be causing this white smoke, but I can’t figure out why it only happened on these two occasions.

Any ideas on what is going on or what I should do would be greatly appreciated - thanks!

“From what I have read online it seems like coolant would be causing this white smoke,”

The one detail that you omitted was what you found when you checked the level of the coolant in the radiator. What did you find?

Sorry about that - So there’s two lines and it says cold fill range between them. The fluid level is directly on the bottom line.

Apparently, you checked the level of the coolant in the overflow reservoir, which can be…less than accurate…when it comes to how much coolant is actually in the radiator.

When the engine is stone cold, remove the radiator cap and see where the coolant level is.
Ideally, it should be right up to the bottom of the filler opening.
Please report back on what you find.

Besides the above, be sure to get the muffler and exhaust inspected. It sounds like it has a rust hole in it; if the exhaust fumes sneak their way into the passenger compartment, can be dangerous.