"Fog horn"/honking noise from front brakes

I have a 2007 Volvo S40 with 81,000 miles. Brand new brakes in the rear, one year-old brakes in the front. Intermittently, when I am coming to a very slow stop traveling less that 20 mph, I get a loud hollow “fog horn” noise just as the car comes to a full stop. My mechanic seems to think it is coming from the left front brake. The sound isn’t a squeak or a grinding-- it’s a low, deep kind of honking. On three different ocassions I’ve had the brakes taken apart and looked at. Most recently I was told that if the noise returns, I should have a brake job done, even though the brakes are still in good shape. Any ideas?

I’d take a wild guess at a stuck brake caliper, but I’d think that if the brakes had been taken apart 3 times, someone would have looked for a stuck caliper and found it.

Have you tried rolling to a slow stop by using only the handbrake? If the noise does not occur then, but only when you step on brake pedal, that would point pretty clearly to the front brakes.

You are correct in that the caliper has been checked out already. Your handbrake suggestion is a good one. I’ll give it a try. Thanks very much for your help.

There is a very good chance that the front pads are just worn despite their age. Your car’s pads include an aluminum strip that will make a very loud obnoxious noise while braking once this strip is reached.
I’ve heard this story over and over. Try getting a second opinion rather than waiting for your current mechanic to declare that you need a complete brake overhaul. New pads cost less than a $100 to replace. An overhaul (pads, calipers, rotors) costs more than $1000, and is probably the easiest and most profitable repair a mechanic can make.