In alt.home.repair, on Fri, 4 Aug 2017 17:29:15 +0000 (UTC), Bram van
den Heuvel wrote:


What diagnostics can I do to figure out why the coolant gurgles after
shutting down?

This happened twice over the past two days on a 30 mile trip each way, both
days of which were pretty hot at around 90 degrees.

Temperature gauge is working as it goes from cold to middle & stays in
middle so the car is not overheating.

Yet, when I shut down the engine, it "gurgles" a bubbly sound.

I can simulate the gurgling sound by squeezing the upper hose, where I can
hear the air and fluid moving about.

I had filled the coolant tank to the Full level, but it spilled out a cup
or two onto the ground when it gurgled.

The fluid is "watery" and "brown" so it hasn't been changed in a super long
time so that will be the first thing after a flush that I do.

I will borrow a pressure tester at the local auto parts store, but that
won't tell me if the water pump is working. The belts are intact and the
fan spins, so, that doesn't tell me much either.

What diagnostics can I do to figure out why the coolant gurgles after
shutting down?

I think when the engine is on and the coolant is circulating, it never
gets that hot. The heat from the hottest parts of the engine is
transferred to a stream** of coolant, but when the coolant stops moving,
that which is next to the hottest parts of the engine get hotter than
ever.

Why this doesn't happen all the time I don't know.

**This is similar to the mistake they make in cowboy and adventure
movies where they are pulling someone up with a rope that is rubbing
against a rock where the rope bends over the edge of the cliff. In the
movies, there is a close-up of the rope gooing over the rock, getting
more and more frayed. But in reality every moment it's a different part
of the rope rubbing the rock so the rock won't ruin the rope.