Kudos to our dealership, but still wondering about this noise

We were noticing a quiet ticking noise when doing light braking at low speed in my wife’s 2017 trim 2. It’s a crisp but quiet click that doesn’t begin until after driving several miles. After lots of miles, it can get a little louder and less crisp. It started before we left on our trip to Ohio and Iowa. Didn’t get any worse or any better. So today, I took it in to our nearby Toyota dealership. It didn’t sound like a CV joint but I couldn’t figure out what it could be. It was faint and only happened at low speed with light braking.

All these stories about “stealerships.” They aren't all like that. The tech and the service manager both tried to chase it down. The service writer agreed to my request to talk to them once they had done their investigation, so we went back in the service area and they showed me what they had found and I got it all right from the horses' mouths. All they found wrong was that the left front rotor had variations in thickness but was otherwise almost like new. I guess that would explain the slightly soft feel to the brake pedal compared to my Prime.

The tech resurfaced both front rotors. He took off about .005” on the left. Right was probably less. He put everything back together and drove it again. It still made the same sound. He continued to investigate and found nothing amiss.

The service writer told me before they started that, if it was the CV joint it would be under warranty. If it was brakes it would be around $200. They worked on it all morning and charged me nothing because they didn’t really fix my issue. (But they did help me not feel like something was falling apart.)

I guess we’ll just keep driving it and see what develops. Maybe it will just stay like that or maybe it’ll get severe enough to diagnose. At any rate, kudos to Sun Toyota for such good treatment of a customer who does most of his own maintenance.

And, if anyone has a Gen 4 Prius that made that sound that way, I’d like to know what you found, if anything. As the service writer took me back to my car when they were done, he said, "You're a real Prius expert!" I tried not to laugh. If I was an expert, I'd know what was making that mysterious clicking sound.

Meanwhile, we'll just enjoy the car. But my Prime is still better.

 

Very clearly from the left front.

They didn't mention checking the rear. The noise is very much from the front.

 

I saw that thread. Maybe I should have posted there but it was getting impossibly long and unfollowable. It does sound like the same issue, though.

As for the "obsolete" TSB, they actually printed that out and showed it to me without me even bringing it up. They said they didn't know why it had been withdrawn but they also said that if it hadn't been withdrawn, they'd have done the replacement. The only reasons I can think of is that either the noise would come back, or the replacement didn't fix it at all. My guess is that the noise would come back.

I like the TAS idea. I think I'll wait to see if it gets worse, though. They claim that they drove another 2017 Prius and it made the same sound. That part, I don't think I quite believe or else it would be generating a lot more complaints if it was that common.

So, for now my plan is to listen and wait to see what develops. I don't think it's falling apart any time soon. There's still plenty left on the drivetrain warranty. And even if it was getting close, it's on record now. And who knows? Maybe it's just the way some of the axles were made that generates that little sound?

Your contributions are always very helpful. Thanks bunches.

 

A valid question. As the rotor spins during braking it pushes the pistons out when they get to points where the rotor is thicker and then, at the thinner places, the pistons apply less force against the rotor until they move back in. But by that time, the thick part of the rotor is back in play. As a result, the pistons spend part of each revolution not doing all the work they should be doing.

Now that the rotors are flat, the braking is considerably more positive. It wasn't scary-bad before, but it wasn't what I know it should be compared the my Prime of the same year.

 

Interesting idea. Not yet, but it's almost due. And I just thought of something else. Sometimes hubcaps can creak at low speeds as the wheel flexes. I haven't had it happen with cast wheels (afaik), but it's happened with steel wheels.

 

Yours sounds similar to ours. The left front rotor actually had two thick spots, so if that was what was making the tick, it would have been roughly the right frequency. But resurfacing eliminated the rotor as a source.

Covid has nothing to do with why I'm waiting and watching. It's just not worth pursuing unless it gets worse. I'll rotate her tires this weekend. Then I need to change the oil in my Prime.

And, btw, I'm glad you have a good dealer.