Rhythmic Brake noise?

I am not going to be much help but I would think it was brake related, probably rotors, but still could be a tire or even a cv joint. I would take it to a good mechanic but if that is questionable, I would take it to a dealer.

 

warped rotors might not show up visually, someone has to put a dial indicator on them.

anything else shouldn't only happen when braking, i would think.

are you feeling anything in the pedal?

 

Since the Prius is 99% brake by wire, the normal brake pedal feedback is artificially created by an ecu. Only when a total control failure occurs would someone actually be directly hydraulically operating the brakes. Most people, thankfully, never experience this because the systems continue to work.

 

I would expect no problems at 70k other than issues caused by age, primarily 12v battery and maybe lights. Brake rotor warping usually occurs when the rotors are very hot from extended use (which normally only occurs on long downhills when the regeneration can't store more power and the friction brakes have to do all the work). When then exposed to sudden cooling such as driving through water the rotors can warp. Yes the brake system lasts a long time. I have put on 250,000 miles on two Prii and never had to do any brake work (that's 125k on the 08 and 225k on the 12).

 

Unless you have gone through a few sets of brake pads or overheated your brakes severely, your rotors are not likely worn. Warped rotors typically won't cause the symptoms you describe - they would cause a vibration in the steering wheel while braking, not an intermittent noise.

Calipers don't really wear out. The slide pins can fail to slide, or the brake fluid seals can leak. Leaks should be detected on a state inspection.

Hybrid brakes are lightly used, because much of the braking is done by regeneration through the electric motor and into the battery. I would take the car out on an empty stretch of road, get it up to 60 mph and stop quickly down to about 20, ensuring you are using the brake pads and not regenerative braking. Repeat that process a few times. This will clean off the rotors and pad faces. If the noise continues and it bothers you, have a shop look at it. The dealer will likely fire the parts cannon at it - rotors, pads, etc. A competent independent shop would be my choice.

 

When was the last full brake inspection?

 

Brakes can pick up something weird at any time, even right after an inspection. They're down near the road and sort of exposed.

I once had a left front on a Mazda that had to have picked up some bit of gravel or a metal fragment or something, made a horrendous screeching noise just as I left work, bad enough that I turned right around into the parking garage and took the brake apart right then and there. I never even saw what the foreign object was, it must have dropped out while I worked in the crummy light, but the sound was gone after I put it back together.

I take it your thump sound recurs at about the wheel-revolution period while you're slowing, and might mean there's a little gouge or scar on the rotor in one spot, possibly put there by a foreign object that is long gone by now. You might spot it without too much trouble if you take the caliper and pads and rotor off and take a good look. A moment with some 100 grit wetordry sandpaper might make short work of it.

It's the Prius Brake Paradox. It's really more or less true. But at the same time, it also leads a lot of owners to say "hey, these pads and rotors have an extended life, I can slack off on regular inspection, right?" and then some little problem crops up that would be no big deal to correct, if caught, doesn't get caught, and eats the pads and/or rotor 100,000 miles early.

There are a few more things that can happen. The "fitting kit" (little springy clips that hold the 'ears' at the sides of the pads) can lose the dry, Teflon-like lube coating they have from the factory, get surface rust, and the pads don't slide freely; they're inexpensive and very quick to change out. The brake fluid seal doesn't have to leak to be bad: another important job it has is to actually pull the piston back in (by all of 0.3 mm or so) when you're not braking, and if it gets aged, cooked, and hard rather than rubbery, it can stop doing that job even if it isn't leaking, and the brake will drag. Even that is cheap (parts-wise) to fix, but more labor; it does require opening the caliper, and air bleeding afterward.

The piston and the slide pins have rubber protective boots that can get punctured or torn, and should be replaced right away if so, to prevent saltwater corrosion of what they're protecting. Also very cheap.

 

2nd full brake job?

 

I mean an in-depth brake inspection, where the mechanic (or you) pulls the calipers off the rotor, lubes the caliper pins, cleans the pads and shims and relubes, cleans the contact points on the caliper, checks the rotor runout and thickness.

Toyota USA recommends this tri-yearly or 30K miles. You should have had two such inspections by now.

This is every six months:



But at 36 months or 30K miles:




FWIW, most owners seem to ignore this, just wait for symptoms. It's preventative maintenance, and it costs a bit. OTOH, it may save you from a bigger expense down the road.

 

you're not gonna get that during a state inspection

in ma, they don't even jack it up anymore. its all about emissions

 

The mechanics who do "brake jobs" are the ones who work in shops, on brutal schedules on the clock, who dare not spend the time to find out what is happening, but just throw the whole bucket of parts at it and hope for the best, which works for them, as they get you to pay for the bucket of parts.

When a mere mortal like you or me works on a brake problem, we don't do a "brake job", we take the thing apart, check condition, measure thicknesses and runouts, replace only what parts need replacing, if any, give a touch of the sandpaper if called for, and put it back together,

So far, my 2010 has needed one fitting kit for the rears (about $16) a couple years ago, and judging by the last look I took, I'll probably want another one next time.

 

With our Hondas over the year, when the dealership was doing brake maintenance, they did a pretty good job I found. But yeah, to quote Stephen King, maybe the world as "moved on".

 

When I was driving an old Ford, those repair manuals were where I learned a lot about the take-your-time, conservative, what-makes-you-think-that-part-needs-replacing-if-some-100-grit-paper-is-enough approach to repairs.

But I had the feeling even then they were kidding themselves if they thought their dealer techs would really read that stuff.

 

Honda Shop Manuals are better than Toyota regarding Brake Inspection: they have a section with that title, and it says specifically what needs doing. I basically fall back on that with our Prius, as far as the scope. The Toyota Repair Manual explains pretty much everything you might do to brakes, right down to a full caliper overhaul, all lumped together, so you need to pick and choose. The Maintenance schedule as well is pretty vague: there's no catch phrase, say "brake inspection", that you can then turn to the Repair Manual to reference.

I think all of this contributes, to owners and dealerships enabling each other, by neglecting brakes.

 

now you've dropped a bombshell. is this the same dealer? seems to me the issues are related.