Weird sounds when I press the brakes only. 2009 Prius with 200k.

All right a couple of things here your link goes to something that's not your video or soundbite The noise you're hearing is emanating from the top of your dash It's like a continuous beep that doesn't stop You press on the brake pedal a bunch of times it'll eventually quit? This is in the interior of your car it's not a squeak coming from a wheel or under the hood? Notice the price is you're paying for a used brake ABS actuator that's the correct part you're showing and your pictures they're 350 $380 for a used part so you want to make sure that you're buying from a seller that won't have a problem changing the part out for you and maybe not forcing you to ship it back because it's not rebuildable once they ship you a bad one technically it should go in the trash or they're just revolving these things around I mean I don't know generally I try to go to a local place or I can physically go remove it myself etc sometimes I'm even lucky in the car still has 12 volts and I can boot the car and see if I have any break codes right at the towing lot and if I have no brake codes I go ahead and take the part off and go and usually then I'm only paying $150 $200 bucks at the towing yard not 380 so you want to make sure that they have another one to sell you or you can get your money back pretty promptly if it doesn't work and who's going to pay the return shipping if that has to happen this is a heavy part so without any of that knowledge that would be kind of a big crapshoot It's a lot of people hustling unknown parts online because they can It's something to do It's like a job without having to go to work you know. So beware of these things going on usually you want to try and find a car locally at a towing lot The guy who picked up the car says yeah everything would go quiet on the dash but it wouldn't start No yellow lights nothing just to check engine light and red triangle etc then you have an idea that you've got a good shot.

 

I've never had that noise in any of my break actuator jobs there is a pounding noise that comes from the other side of the car when that other little brake pump is starved the fluid or has air in it but it's more like a radiator hammering in a European home. That there sounds like something's going on with the heat or the damper door or the coolant control valve or something along those lines I guess it could be the brakes Do you feel those vibrations in your brake pedal at all I mean I would hate to think the accumulator pump sounds like that but I've never recorded it before out I'm driving a car with the bad brake pump right now and it doesn't make any noise like this outside of the car you can hear the brake pump ing more than normal because the accumulator leaks and has to be pumped back up way more often than it did when it was working properly and usually it's a light rattling noise very light sounds like a electric tire compressor that you plug into your cigarette lighter but much quieter but the same kind of pumping noise just very quiet almost like a cat purring

 

The thing that's connected to the pedal in the generation 2 Prius is called a stroke simulator today it would have been called the master cylinder years ago just so we're clear I guess on what the book is going to call it that stroke simulator by looking at it looks to be all hydraulic with no power or anything associated with it It just pumps fluid when you push the pedal over to the actuator which takes that input of fluid from the stroke simulator and runs it through all the nonsense that the actuator will do linear offset valve and all of that so I don't actually think that the stroke simulator could make any noise generally speaking of its own accord because it is like a master cylinder on the firewall without the brake booster behind it look with your flashlight so I would have to figure out how I could get the stroke simulator to make that kind of racket even if it was run out of fluid it wouldn't pump nice but I don't think it would make a noise It's hydraulic there's no motor attached to it other than when your foot is pushing down on it I don't think it's capable of making noise and even with your foot pushing down on it unless you were to pump it erratically and really fast I wouldn't think it would make any noise just go to your well maybe not today but go to any '90s Toyota Corolla and pump the brakes You're essentially doing the same movement you're doing to the Prius so I'm not sure the stroke simulator or the master cylinder could make this noise The pump and accumulator the big aluminum block to the right of that when you're sitting in the car of the strokes emulator could possibly and does make some noise you hear a pump running things like that when it's running when it's worn out and not working properly and getting ready to fail it starts pumping a lot more so every time you get out of the car walk away from the car be outside doing some yard work you'll constantly hear the car making that pumping noise seems like it never ends.

 

All the brake business is on the firewall on the other side of where you're sitting so it's got to be a pretty decent sound to get through and be heard while you're sitting in the car and going down the road and pushing the brakes every so often but you're there and it's your car so there's always that I guess I would get my son or friend to sit in the car and mess with the brakes while I'm sitting there with my mechanics stethoscope and my listening ears and listening but that sound to me sounds like some sounds I got going on with vent location for the blower the thing hunts for the position you've selected and it sounds almost like that but that's in my car which is sitting right here which I can see and work on.

 

Nah, the gen 2 master cylinder is connected to the pedal and it's called the master cylinder. The stroke simulator is a different part in a different place under the hood.



The master cylinder in a gen 2 is just like the master cylinder in your granddad's car. You push the pedal, it pushes some fluid.

The stroke simulator is just a piston on some springs. It's where the fluid goes when you push the master cylinder, and the springs are chosen so it feels like you're pushing real brakes.

The actuator is where everything else happens. It senses the fluid pressure you are putting on the stroke simulator, and the ECU under the dash decides how to make the car slow the way you want it to, and the valves in the actuator send the right amount of pressurized fluid from the pump and accumulator out to the real brakes. (The pump and the accumulator are the two round greebles you see on the actuator there.)

 

So the stroke simulators on the opposite side fender well of the driver it's the thing that looks like a little pump mine is hammering or was hammering like crazy sounding like a radiator and a old house in the EU and I could put my hand on it and feel it I thought it was another some kind of booster pump for the rear brakes or some kind of nonsense like that because it kept just hammering away even when I mostly when I was out of the car in the car was off this thing would hammer away for you know good few seconds until it would finally quiet down and oh well I don't think it's bad I think it's having problems with fluid moving not moving something going on because before I changed the bad actuator that was on the car and the thing was not hammering to the accumulator thing that I changed to which is also bad but has caused this thing to hammer that settle down in the last few weeks and now it doesn't do it so I don't think it's bad that's an awfully weird device and weird thing to call it a strokes emulator good grief no wonder Toyota have so many problems with these cars.

 

It's definitely weird because the lines coming out of that stroke simulator thing over there right behind the reservoir on the passenger side of the car look like it is predominantly connected to the rear brakes so maybe it's for simulating the stroke for the rear brakes. As they're not connected to something or they're independent or something like that who knows.

 

Coupla months in the laboratory can save ya a coupla hours in the library ...



As you see, the only tubes attached to the stroke simulator are one from the master cylinder and one to the actuator on the firewall. Maybe some tubes run close together and you ended up looking at some rear-brake ones that were nearby.

In normal operation (SMC 1 and SMC 2 closed), there is no stroke-simulator fluid going anywhere farther than the PMC 2 pressure sensor, where the car sees how hard you are pressing the pedal and decides how strongly you feel about stopping. The piston and spring in the simulator supply you with all of what you feel like you're doing on the pedal.

In fail-safe operation, there is no stroke simulator (the SCSS valve closes), and SMC 1 and SMC 2 open, so the two independent lines from the master cylinder go straight to the two front brakes.

Those two 'independent' lines are separated by a movable piston inside the master cylinder so a leak in one of them doesn't lose you the other, but except in leak situations the pressures both sides of that piston are equal. Most master cylinders have worked that way for a long time.

 

Go over on the passenger side of the car and look right behind the brake fluid holding tank or reservoir You see that silver thing on the frame rail inner fender well area looks like a little pump it has a zerk bleeder fitting on it It's the first picture in the drawing that Chapman f posted that says strokes emulator looks like a little pump that thing if it's doing that noise you'll be able to put your hand on it and feel it it'll be hammering like an old radiator at least mine does and or it did and it was quite loud initially I got used to it and then it just stopped I don't know what's changed here but anyway that part was never suspect in my situation at all It just started making the noise while I was changing the break actuator My bad one for another bad one I've got to find a good one but that hammering eventually just stopped and did it for about a day but it sounded a bit louder than your microphone was picking up and it was all coming from the right hand side right behind the brake reservoir you'll see the silver thing it's got I think a red Toyota sticker on it I didn't try to read it I don't think it says stroke simulator on it but whatever I don't care what it is that thing was making a racket like two Pistons were bouncing back and forth uncontrollably or something along those lines similar to the two pistons that would be in a wheel cylinder kind of I didn't know the strokes simulator was a item that ever got replaced I've never heard of anybody but I haven't really looked either but that's interesting It would seem to me it would just be getting a bad signal from the actuator or something and that would make it go nuts That's why I figured my actuator was sending some kind of bad signal to the system and causing that thing to go nuts

 

The stroke simulator is nothing but a cylinder with a piston and a spring in it. It would have to be about the last thing I would ever think of in any problem with the brakes.

The only other thing that's on it is an electric ON-OFF valve that blocks it off if the brakes go to fail-safe mode.

If flaky power to that valve is making it clack open and closed, that could be a source of Tombukt2's noise, and might also be the first and only report of any such issue on PriusChat. I sure don't remember any others.

 

FYI, Your image is not showing up for me today.