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Discussion Starter · #1 ·
Well. Some headway, though not much.

Went to dealer (Power Toyota, Irvine CA) and told them of the sound. Within an hour I was told all was well, that my car did the same thing that another Prius in the shop did. I asked if they could tell me what it was, and they said it was the thermos bottle pump. I said no, that's another, softer, purring sound. This is different. Essentially I was dismissed, and my car was brought out but I refused to be brushed off. I asked to speak with the tech, but that eventually was denied. So I declined to leave, and left my car in the pick up area (a little rude, but it got the further attention I wanted).

After a bit one of the managers of the service dept came out to speak with me and said that they thought it was part of the computerized system that is constantly monitoring the car (even when off?) and hinted that the tech didn't know everything about the car, that Toyota doesn't want everyone to know its deepest tech secrets or the like. Luckily while we were chatting the car (off for at least 10-15 minutes now) had three or four ten-second buzzing fits. The fellow admitted that it didn't seem like a normal thing to him.

And so then he said that on Tuesday a roving Toyota service rep will be visiting the facility and he said I should come by and leave my car for the day, and will be given a rental in exchange. Maybe then they will get to the bottom of the buzz.

I got to talk to the owner of the other Prius, by the way, and described my buzz to him. He said he'd not experienced anything like it. Makes me wonder again if I was just getting a brush-off.

It's hard to know what to think here. It's very annoying that I was not allowed to talk with the technician. It would have have been so simple to have demonstrated the sound to him. Or they could have shown me that another Prius did the same thing. I don't think others do this. It's a little disconcerting that their "master tech" apparently doesn't know what the car's components are.

So that's the story for now.
 

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As nice as my dealer is, and as little that he knows about one of his products that he has been selling for several years, and because the reason I bought my car in the first place was to determine if hybrids are going to be the car of the future, I do now believe that the Prius is too technology advanced for the normal car market, and that the auto industry will be going much lower on the tech pole for the cars we will be driving during the period before the hydrogen cell. More like Honda's much simpler and less refined version of the hybrid.
At Honda, where their models are more car than hybrid, you can get a question answered by any of their "wrench's"
In the meantime, I will be enjoying the exceptional milage of my Prius.
 

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well you should have been allowed to talk to the tech yourself at the very least. i don't believe or trust in any dealer that won't let you do that.
 

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A buzzing noise occuring while you were talking sounds very much like the accumulator pump. That will operate a couple of times when off. So will the coolant storage pump operate briefly to be sure the thermos is holding the coolant temp properly.

From what I have heard, perhaps it was from Galaxy's husband through Galaxy, that it is your right to speak with the tech. I would complain to Toyota HQ that you were denied that right.
 

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it's hard to diagnose a car over an online forum, but since DanMan mentioned it...

DH told me it might be the accumulator pump, and that it would run very frequently if the ABS system was somehow losing pressure. it's also located in the right place to match your observations of the location of the vibration.

of course, since he can't actually hear the noise and can't tinker with it himself... it's just a shot in the dark.

sounds like there's a big communication problem at the dealership there. why they don't let you talk to the tech, is beyond me. it would greatly simplify things if you could show him exactly what your concern is rather than having him learn about it through the interpretation of the writer. and even if there really is nothing wrong with the car (which i'm not saying, that doesn't seem right) at least the tech could explain it to you better than a service writer or manager could. oftentimes, DH has the customer take him out to their car and show him what the trouble is before they leave. it helps him and the customer usually appreciates it.

if possible, once this is over, i'd take my car elsewhere for service if i were you. the advice i give to everyone is find a tech whose work you are happy with. of course, being able to talk to the guy helps... but anyway. once you know the guy knows his prius guts, stick with him and tell him you'll be asking for him for future services. benefits all around. the tech will be able to give you more personalized service and you will know who's under the hood of your car.

and of course, just because someone's an ase master and a prius tech doesn't mean he's got the talent necessary to make a good prius tech. base your conclusions on the work he does.

that said, i wish you luck in getting this corrected.
 

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galaxee said:
well you should have been allowed to talk to the tech yourself at the very least. i don't believe or trust in any dealer that won't let you do that.
That's sad to hear. I took my baby to Power in Irvine one time to have them hook it up to the computer and change the defaults on one of the climate control settings (gratis!).

The tech came out to talk to me when I dropped it off and when I picked it up. The service writer seemed to know what she was talking about too (as far as the Prius was concerned). I was planning on using Power for any future service. I'm disappointed to hear they've let you down.

Please let us know how all this turns out.
 

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galaxee said:
it's hard to diagnose a car over an online forum, but since DanMan mentioned it...

DH told me it might be the accumulator pump, and that it would run very frequently if the ABS system was somehow losing pressure. it's also located in the right place to match your observations of the location of the vibration.
Now that makes a lot of sense. I have seen posts of an accumulator pump freqently firing up because of a pressure leak. Not enough to cause brake trouble, but enough where the pump has to operate more frequently. And I believe the pump is shut off when the car is left alone for a long while. Otherwise it would drain the battery
 

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According to the Prius brake specialist I spoke too, the electric hydraulic pump operates along with the aid of an accumulator to keep hydraulic pressure in the system. It should not operate for more than a few seconds normally unless you are constantly "on the brakes." Now if you have a pressure loss in the system and the pump operates more than a few seconds (to keep pressure up in the accumulator) the BCM will give you a RED BRAKE warning light on the Dash. If you find no fluid under the car indicating a hydraulic leak the problem should be isolated to the accumulator. If this occurs the BCM will also cause the RED BRAKE warning light on the dash to eliminate. The reason the accumulator is in the system at all is to keep the electric pump from operating continuously. Without the red brake warning light illuminated I would say the pump is not causing your buzzing sound. If it is, and if you have no warning light I would have the entire braking system gone over by a "good" dealer.
 

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If the 'leak' is slow enough, it won't set off a DTC, as it can seem normal to the computer, yet not normal to us.
A hold on the brakes should not run the pump often. A constant change in braking would.
 

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Discussion Starter · #10 ·
Buzz-3

DanMan32 said:
If the 'leak' is slow enough, it won't set off a DTC, as it can seem normal to the computer, yet not normal to us.
A hold on the brakes should not run the pump often. A constant change in braking would.
Galaxee, hyperion & DanMan have it -- it's the ABS system, they finally determined near the end of the day yesterday. And today I am told they will test it to see if it's within spec or not. If not, I get a new system/component/doohicky; if it's still in spec, then I get to drive it until it fails. Lovely prospect, I really don't want to drive in dread of an imminent system failure in future.

BTW, due to all the thought of it being the brakes, I paid more attention to same on the way to the dealer yesterday. I found (and mentioned this to them) that if I kept firm pressure on the brake pedal while at a stop light, I could eventually get it to clunk to the floor. The writer said he'd seen that happen with these cars before and didn't seem worried in the least. So I'll try not to be worried, but hope that nonetheless it will count toward a failing grade on the system.
 

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Cattmatt, if you keep your foot on the brake pedal with an even pressure, and it eventually goes to the floor, you definitely have brake problems. It sounds like a leak somewhere...
 

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" if I kept firm pressure on the brake pedal while at a stop light, I could eventually get it to clunk to the floor. The writer said he'd seen that happen with these cars before and didn't seem worried in the least"

Tell this to a Customer Service person at the regional level (in other words, above the dealer) and you will get action fast. This is not normal, and someone with two brain cells to rub together will realize the HUGE liability they take on by ignoring this obvious problem.
 

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if you have a slow leak, that's dangerous. you might not be able to do a panic stop in time because the accumulator won't have pressurized the system enough. your stopping time may be delayed.

who the #%$& waits for a brake system to FAIL before replacing components??? a good dealer will not only stand behind their brake system work, they'll stand in FRONT of it. (ha. ha. but true)

i would definitely get on the phone ASAP.
 

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Some service managers are relying on the dual red brake warning light to illiminate and that you will stop immediately and dig out your manual which will advise you to not attempt to move your car but to get it towed to a dealer. Those red light warnings advise of possible complete brake failure. (however, there is one other "fail safe" unit in the brake system) In your hydraulic lines are a couple of electrically operated supplemental very small "master cylinders". If the BCM senses complete pressure loss these cylinders can supply a couple "shots" of hydraulic pressure as long as there is fluid in the system. This is the only change to the old Bosch system the Prius system is based on. (this info all from a touring Prius service tech.)
The service manager at my dealership listened to the whole lecture that I got and still doesn't have a clue. So I am not surprised at what you've been told. I did have a "total" brake failure at one time with the original bosch system, of course in another car. At that time I had a total failure of my accumulator and the system unlike that in the Prius did not illuminate the brake warning light as the electric pump now running all the time was still supplying pressure. Down the road in the time frame, and I have no guess how long as the electric pump was very quiet, the pump "gave up", I got a red warning light and after four brake applications had total brake failure. Of course I was not the first, and account of prior knowledge, had my car in a breakdown lane and stopped before the total loss of pressure. Moral of the story, "don't fool with a red brake warning light. You will probably never see one but if you do, pay strict attention, and stop while you are able.
 

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another thing to add- the brake pedal isn't direct connected. it's a brake-by-wire system. why it's falling to the floor has nothing to do with system pressure but sure isn't NORMAL by any means.

give these guys hell and go elsewhere. i can't believe it took a regional service guy to figure out you had an ABS problem. talk to the region guy again about the guy who told you to drive it until it fails. that's wrong, plain and simple.
 

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Uh, pedal to the floor is indeed normal. As you said, we aren't controlling the brake wheel cylinders directly. There is a stroke simulator to get some feel of a normal brake, but not completely the same. What you basically have is a spring loaded brake pedal with hydraulic damping.

As for a small leak, it doesn't necessarily mean a leak of fluid out of the system but rather pressure is lost back to the reservoir.
The system has 2 electronically controlled valves for each wheel cylinder. One adds pressure to the cylinder from the accumulator, one relives pressure back to the reservoir. There's also an overpressure relief valve on the accumulator. Any one of these could have a slight leak where fluid passes through, but not enough to cause a problem. It just won't hold pressure and has to be replenished by the pump. As long as the pump stops, you have enough pressure. If the pump kept running trying to keep the pressure up, then you have a problem.
 

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Discussion Starter · #17 ·
Buzz-3

Vindication!

Finally got a call late yesterday afternoon from someone (other than the service writer who'd told me on Saturday that nothing was wrong and who was supposedly my contact for this visit as well) who told me that it had taken most of the day but they'd determined that there was a problem with the accumulator or other aspect of the brake system and that a new one was being ordered. When will it arrive? Couldn't say.

They pointed out that although the sound is a normal one, it's happening waaay too often. (Now, gee, what was my original complaint? I think it had to do with this buzzing happening before the car starts, about twice a minute while driving, and cycling for some time after the car was turned off. Yup, sounds like a match to me!)

Given that they didn't know when the part would come in, I asked if I could use my car until the part arrived, but now (as so many of the recent posts point out so clearly) they are recommending that I not drive the car, despite there not being any warning light as yet. This tells me that they are worried about imminent failure, the thought that had crossed my mind on Saturday and which drove me to insist on a second opinion. I'm glad I didn't just give in and blithely ignore it! And an interesting reversal on their part.

So I get to keep using the loaner Camry for a couple more days, I guess. I hope that spare parts are not is such short supply as the cars themselves!

Thank you all for your concern and helpful ideas/cautions/suggestions.
 

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'Tis a shame that some dealers and reps have to be so dismissive.

Happy to hear that they are reacting and that you have a safew loaner :lol:
 

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We should write these things down.

"Symptom: buzzing noise when car door is open, even with car power in off state. Buzzing is continuous or intermittent about every 2 minutes.
Probable cause: small fluid pressure loss in accumulator causing accumulator pump to engage too often."
 
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