I have a 2000 Toyota Avalon with over 200,000 miles. It has been running well, but started a new noise a couple of months ago. When the car is warmed up and the accelerator is in the right position, it makes a “whoop, whoop” noise, similar to the noise a zoo seal would make. This can happen on flat highway, going uphill or downhill, or even when in park. The only thing that makes it stop is adjusting the position of the accelerator. Three mechanics have had the car and were asked to find out what is causing it, but none have been successful.
Seals make a barking sound that is similar to a pulley with a dry or worn out bearing. Pulleys have a rotational mass that has a resonant frequency, meaning that they will vibrate the most at certain speeds. The sound could come from any of your belt driven items or a tensioner pulley. It could also be the water pump or timing belt tensioner or even the timing belt itself.
We just replaced the timing belt and the water pump, so it’s not those things…