If you’re lucky, overheating caused by cooling fan

Dear Car Talk: After weeks of visits to two different mechanics, more than $1,000 paid in repairs and three tows in two weeks, I am finally desperate enough to write. I want to extend the life of my 2002 Buick Rendezvous. I inherited it after the engine had been replaced in 2007.

We found we needed to add coolant about every six months, until a couple of months ago when the temperature gauge suddenly went red.

We added coolant and our mechanic replaced the thermostat and flushed the system. Days later, it happened again, and the SUV died on me, but miraculously it worked fine once it got back to the shop. I was told it had a “bubble in the coolant line.”

Two weeks later, it overheated again, and a new mechanic replaced some parts for $700 — he said the tubes might be clogged in between the radiator and engine. On the way home, it overheated and died. So, back to mechanic No. 1 for a new radiator AND another new thermostat.

All seemed finally to be healed, at least for a week. Then, my son drove the Rendezvous for 2 hours on the highway, and when he came to a stop at a red light, the temperature gauge went red again, then went back to normal by itself once he started driving again.

It happened twice more on his way home. The car has been sitting for a week while we try to figure out what to do next. Any suggestions? Kind regards.— Mrs. Martinez

Are you sitting down, Mrs. Martinez? If you’re incredibly lucky, and you’ve lived a good, clean life, you might just have a bad cooling fan.

When the engine is at operating temperature, and you’re on the highway, you get plenty of airflow to cool the engine because you’re moving. But once you’re stopped, the natural airflow stops, and you need an electric fan to blow air through the radiator.

So, check and see if the cooling fan is cycling on and off like it’s supposed to. If it’s not, maybe the radiator solved the problem, and all you need is to fix the cooling fan. If the cooling fan IS coming on and off, then the news is far more serious.

Most likely, you needed a radiator from the very beginning. But, unfortunately, during one of those four (or 14) times you overheated the heck out of the engine, you blew a head gasket or cracked the head. Or worse, cracked the block.

So, start by figuring out if the cooling fan is working. If it is, ask your mechanic to test for a blown head gasket or cracked head or block. We use a dye test, or we test the radiator vapors for the presence of exhaust. If the tests come back positive, and the rest of the car is still in good shape, then it’s time for engine No. 3, Mrs. Martinez.

And this time, ask them for one of those punch cards, so after you get to your 10th engine, you’ll get the 11th for free.