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Brake fluid level high

Discussion in 'Generation 1 Prius Discussion' started by ronlewis, Mar 27, 2024.

  1. ronlewis

    ronlewis Active Member

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    Haven't driven this car in years. Got it out and just going up and down the street, the brakes are spongy and weak. Pedal real soft at start up. The reservoir is over full, noticeably higher than anyone would fill it. I'm not getting brake alerts yet, but I've only driven a mile. Any clues where to start? Where is the extra fluid coming from? A frozen caliper maybe?
     
  2. Tombukt2

    Tombukt2 Senior Member

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    Check the 4 wheels. For air.
     
  3. ronlewis

    ronlewis Active Member

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    Yeah, I was reading up on the bleeding process.
     
  4. ChapmanF

    ChapmanF Senior Member

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    The system includes an 'accumulator', which contains some of the brake fluid during normal operation, and makes the level in the reservoir look low. When the system isn't in use for a while, that fluid slowly goes back to the reservoir, until the accumulator pressure is zeroed down.

    The level marks on the reservoir are designed to be checked when the system is zeroed down. Sometimes, a person who doesn't know that will look at the level while the car is on (or was recently on), and think it looks low, and "top it off". Then later, if you look when it's zeroed down, it will be overfilled.

    Yours shouldn't stay zeroed down when you turn it on, though. You should hear a buzzy pump sound for a few seconds and the reservoir level should drop a bit. Is that not happening?
     
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  5. ronlewis

    ronlewis Active Member

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    I haven't checked yet. Just reading. It says to check for the pump stopping, and I assumed that was by listening. Dang, I hear so badly. I hope I can hear it. Late now, but I'll check it tomorrow. thx.
     
  6. ronlewis

    ronlewis Active Member

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    What's this about? Exhaust Brake Actuator Genuine Toyota 1723021010

    Does that description sound right? I thought that actuator let exhaust recircle for pollution purposes, not braking. Either way, those are some high-dollar parts. Maybe I need to post my spares for sale.
     
  7. Trombone

    Trombone Member

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    It's part of the pollution control in the engine exhaust line; has nothing to do with braking AFAIK. The description is bonkers. Had I known that this was available as a separate part, I wouldn't have had to replace the entire exhaust line in my '02, which cost a whole lot more than this part, believe me! The problem is that the actuator is underneath the car where it is exposed to all of the corrosive elements that are flung up against it from the roadway, and over time (20+ years in my case) it ceases to function and throws a code (I forget which one). The car is drivable without the actuator, but mileage suffers a bit, and I don't know whether car could pass emissions test in PA without it.
     
  8. ronlewis

    ronlewis Active Member

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    Yeah, I was just describing that to the guy in the other thread. I hadn't read that part about the brakes, but he's getting a Brake alert with his P1347 code for the stuck actuator.

    I stumbled on that part googling just "brake actuator." It was pictured in the suggested results from multiple vendors.
     
  9. ronlewis

    ronlewis Active Member

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    But, I guess it might make sense that blocking the exhaust could help braking. That's how the big trucks work.
     
  10. ronlewis

    ronlewis Active Member

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  11. Tombukt2

    Tombukt2 Senior Member

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    What is that thing do close the exhaust off?
     
  12. ChapmanF

    ChapmanF Senior Member

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    That's a stupid random mistake in a part name in an online catalog.

    The part in the picture is the exhaust HCAC actuator. HCAC is hydrocarbon adsorber catalyst. It has nothing at all to do with the brakes.

    The gen 1 catalytic converter is inside an inner shell, and there's an outer shell around it containing a material that can temporarily adsorb unburned hydrocarbons.

    After startup, when the catalytic converter is not yet hot enough to convert the hydrocarbons, the valve is closed and the exhaust is forced through the adsorber. Once the catalyst is hot enough, the valve opens, and the stored hydrocarbons get purged out of the adsorber and go through the catalyst with the regular exhaust. Under decelerating conditions, when there is no fuel or combustion and the engine just pumps clean air, the valve closes again and uses the clean air to scavenge the last of the hydrocarbons out of the adsorber.

    [​IMG]

    It has nothing, as in absolutely nothing, to do with the brakes. Somebody, or maybe some AI autocorrect, apparently one day said "what's HCAC? oh, you mean brake, right?"

    I see if you search for that part number, now you find lots of sites that call it the "exhaust brake actuator". Just goes to show that once one site on the internet makes some goofy mistake, a hundred other sites that copy from it will have the same mistake.
     
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