wrote:
I have a 2001 S10. For a few years now, it has been losing coolant. I
just added a full gallon to the overflow container. I have done that
before, maybe three times now.

I see no evidence of leakage under the truck. Performance seems just
fine. I am wondering....could I have head gasket leakage? Should I
fix it? The truck has 90K miles on it, and has had zero repairs. Uses
no oil.

Thanks

Wei

Since this a home repair newsgroup, you should remember to start the
subject line of non-home-repair related posts with OT so that members will
know that your post is "off topic". At first I thought this might be a
central air conditioning question.

That said, an automobile's coolant system will sometimes only leak when it
is under pressure. The pressure goes up as the engine gets hotter. The leak
then hits the hot engine and evaporates before you ever see it. By the time
the engine cools enough to no longer boil off the leaked fluid, the leak
stops because the pressure goes down. The result is that you won't see any
fluid under the truck.

An auto repair shop can pressurize the system while it is cool and
sometimes reveal the leak. It often doesn't take much pressure to find a
leak in a cracked hose or loose clamp.