Brake pedal hard

Maybe you should get your brakes check, along with the clunking sound. You have a strange sound and brake problem symptoms.

 

How long ago did you bleed the brakes? Was this trying to deal with this symptom or could it of contributed to the problem? Prius are bit weird with brake bleeding and while it requires using Toyota Techstream software, some people have been able to do it without.

 

There is a non-Techstream method in the repair manual, well for bleeding the brakes, which can amount to the same thing. I understand from @ChapmanF the non method is not effective if you’ve got air in the brake booster. But for reg fluid change seems fine.

 

Yep, did it with my mechanic and no problems.

 

Is this different for Gen3 compared to Gen2?

Or maybe that should be my personal tagline every time I post to the Gen3 forum?

 

Yeah gen 2 Repair Manual doesn't say anything about non-Techstream method, using "invalid mode". It might be worth a test, for anyone with a 2nd gen, to try the invalid mode chicken dance, see if it works.

 

Under most "normal" conditions, there should be NO ABS rattle.

I think you are right to be mildly concerned and need help from a qualified shop.

 

Precisely, and that's why the repair manual specifically calls it a non-Techstream fluid replacement procedure, and does not call it a bleeding procedure.

As long as you are doing pure fluid replacement, on an already properly-functioning system, with no bubbles in it, the procedure is adequate.

Dealing with bubbles requires bleeding, a different job that does not have a non-Techstream procedure in Gen 3. (You can get by with some improvised procedures if your only bubbles are in lines downstream of the actuator.)

 

That's interesting: there is no mention of invalid mode in second gen manual, at least not in the pdf I have. There is mention of "ECB invalid", but no chicken dance description.

 

Ah whoops thought you were dealing with 2nd gen, my mistake.

 

If you have a hard brake pedal you may have the dreaded nitrogen leak. Be careful I hear you can lose all brake boost at once when it fully goes. You can probably still drive the car but if you are a small human or not expecting it you can get into some trouble. Yup my 2010 also has the garbage abs. I just know not to hit the brakes over big bumps on my off ramps on my commute for this reason as it cuts the brakes excessively for the rest of the ramp.

Also, even though this was a tsb that effected our cars they pretty much made it impossible to take your car in to get it fixed when i asked about it probably 5-6 years ago.

 

In Gen 3 there are two, absolutely distinct, causes that sometimes get mixed up.

The accumulator does contain a metal bellows with pressurized nitrogen on one side (that's the way it's built in all generations). If that develops a leak, then nitrogen does get over to the wrong side of it, so there's some gas in the brake fluid, and less gas on the other side where it's supposed to be, and the result will be more frequent pump running, just like in a residential well water system when there's not enough air in the pressure tank.

There was a bad batch of accumulators in the first year of Gen 3, covered by recall D0H. The metal bellows inside had been manufactured slightly too small, so it banged on the inside walls of the accumulator while driving, and developed early cracks. (Of course that doesn't mean the non-defective ones can't ever wear out; nothing lasts forever. But the undersized ones failed early.)

That issue can give you extra-frequent pump runs when you use the brakes, but it will never explain an issue where the pressure leaks down continually even when you're not touching the brakes and the pump just continually runs. That is an internal hydraulic fluid leakage, nothing to do with nitrogen from the accumulator.

That hydraulic leakage is what the ZJB and related service campaigns are about. The NHTSA investigation into it was focused on hydraulic valve wear.

So, if you'd like to learn more about the nitrogen leak, you can look up "safety recall D0H" (and its technical instructions, T-CP-D0H-A510-D).

If you'd like to learn more about the hydraulic leak, you can look up "customer support program ZJB" and its related investigation.

You can find both at NHTSA's 2010 Prius page, scrolling down to the Recalls & Safety Issues section. Four tabs are there, Complaints, Recalls, Investigations, and "Manufacturer Communications". A recall (like D0H) is under the Recalls tab, while a "customer support program", like ZJB, is under the Manufacturer Communications tab. The investigation related to ZJB is under the Investigations tab. (The Complaints tab is pretty much unmoderated irate-owner submissions, so it's not much different from stuff you're used to reading on yelp, etc.)

 

The pump's job is to create the pressure by pumping fluid into the accumulator bottle that stores it. With the system in good condition and not leaking, the pressure stays high in the accumulator without the pump having to run much.

The pump just runs like the well pump in a house with well water: turns on only when the pressure gets below a cut-in point, then turns off as soon as the pressure is back above a cut-out point. Pump running less frequently is what you want.

Using a scan tool that can retrieve the skid ECU live data list, you can watch what the pressures are in the accumulator and the brake lines.