Tom Magliozzi, who with his younger brother, Ray, hosted "Car Talk," for years the most popular entertainment show on NPR, died on Monday at his home outside Boston. He was 77.

The cause was complications of Alzheimer's disease, NPR said.

The weekly hourlong "Car Talk," which was broadcast for more than 30 years, was supposed to be about mechanical problems with cars, but the format was mainly an excuse for the brothers, known as Click and Clack, to banter with callers about the mysteries of life, as viewed through an automotive prism:

Why does a car suddenly stop working? Should I give this clunker one more chance? Why won't my husband pay for a mechanic to fix our car?

Callers would frequently reproduce a strange noise their car was making, and the brothers would offer an instant diagnosis. In a segment called "Stump the Chumps," selected callers would be asked if the advice they had received proved to be correct.

At its peak, "Car Talk" reached more than 4 million listeners a week — more than any other NPR entertainment program, network executives said.

The brothers stopped producing new shows in 2012, but taped episodes are still heard on 660 stations, with an audience of 3.2 million. This weekend, Ray Magliozzi plans to use the show to offer a tribute to his brother, said Doug Berman, who has been executive producer of "Car Talk" since it went nationwide in 1987, 10 years after it was first broadcast in the Boston area. The show will be renamed "Best of Car Talk."

On the air, the brothers were a team, swapping stories, chortling at each other's jokes. Ray, who is 12 years younger, is higher pitched; Tom had the deeper voice and a laugh that tended to run away with itself. Both had unmistakable Boston accents.

When asked who was Click and who was Clack, "they said they didn't know," Berman recalled.

Thomas Louis Magliozzi (pronounced mal-YOT-zee) was born on June 28, 1937, in a largely Italian-American section of Cambridge, Mass. He was the first in his family to attend college, NPR reported, earning a chemical engineering degree from the Massachusetts Institute of Technology in 1958. His brother graduated from MIT in 1972.

In addition to his brother, Magliozzi is survived by a sister, Lucille Magliozzi; three children, Lydia Icke, Alex Magliozzi and Anna Magliozzi; five grandchildren; and his companion of recent years, Sylvia Soderberg. He was married and divorced twice.

By his own account, after graduating from college, Magliozzi took a conventional path as an engineer until experiencing his "defining moment" after being involved in a close call on the highway.

He described the incident in 1999, when the brothers shared a commencement speech at their alma mater. Tom described driving on Route 128 to his job in Foxborough, Mass., in a little MG that "weighed about 50 pounds" when a truck cut him off. In the aftermath, he thought about how pathetic it would have been if he had died having "spent all my life, that I can remember at least, going to this job, living a life of quiet desperation."

"So I pulled up into the parking lot, walked to my boss' office and quit on the spot."

The brothers started a do-it-yourself car repair shop in Cambridge called Hackers Heaven, but found that their clientele needed more than some workspace, a few tools and occasional advice. So they changed the name and philosophy and opened the Good News Garage, a traditional auto repair shop, which is still in operation.

After appearing on a local public radio station, WBUR, the brothers were invited to appear on a new national show, "Weekend Edition Sunday."

Nine months later, in 1977, "Car Talk" was its own show.