I'll keep this short. Scout's honor.

On Friday my son and I drove to a trailhead for a weekend hike. The last
8 miles of road are washboardy, gravel, and steep uphill in places (rear
wheels juddering on the gravel). When we arrived I noticed a small
puddle under the rear of the van. I took a look at the refill tank
(behind the licence plate) and the coolant level was up to the lower
edge of the filler cap, and the outside of the tank was wet. It was a
cool morning and at no time did the engine get hot. I've driven this
road before, and rougher ones, with no incident.

I didn't look any further into the situation, we wanted to hit the trail
and whatever had happened could wait until we returned.

On return I was not happy to see that the puddle was still visible, but
maybe coolant doesn't evaporate clean like water. I worried

The refill tank was bone dry. The expansion tank was completely full,
and it looks like just plain coolant.

We filled the refill tank to the "max" line with clean water (about a
liter) and drove off.

We stopped several times on the 130 mile trip home to check the level in
the refill tank and due to the warm engine, it was higher, about 1/3rd
up the filler cap. There were no leaks. When I got home, the level was
still 1/3rd up the fill cap.

This morning, the van cold, the coolant is back to the "max" line.

I was worrying about a head gasket leak or something pressurizing the
cooling system.

But now I think that the more likely explanation might be that the cap
was a little loose and when the coolant expanded it drooled out of the
refill tank. I'm not convinced, though, since the last time I did
anything with that cap was back in April and I've driven a couple
thousand miles since then, on equally rough roads.

Given this information, anyone care to offer another theory about what
might have happened?

--
Jack "Rocket j Squirrel" Elliott
1984 Westfalia, auto trans,
Bend, Ore.