Brake booster question

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Sep 7, 2022
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Hello guys I have a pretty different issue with my brake booster on my 06 lx470. The pump comes on about every 5-6 brake presses during normal driving, and I can feel it vibrating through the brake pedal when the pump is running. But no codes, I am sure you are not supposed to feel or hear the pump running right?
 
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San Antonio
Hello guys I have a pretty different issue with my brake booster on my 06 lx470. The pump comes on about every 5-6 brake presses during normal driving, and I can feel it vibrating through the brake pedal when the pump is running. But no codes, I am sure you are not supposed to feel or hear the pump running right?
Check the health of the booster by pumping brakes ~40 times with key out where you’ll feel pedal drop. Turn key to on, not start, and time how long the pump runs for. Also look on the reservoir cap to properly check fluid level.
 
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Check the health of the booster by pumping brakes ~40 times with key out where you’ll feel pedal drop. Turn key to on, not start, and time how long the pump runs for. Also look on the reservoir cap to properly check fluid level.
Thank you for the reply, after pumping the brake about 50 times, then turn IG on, the pump runs a total of 42s to stop, in those 42s the pump stops for less than 1s for a couple of times, so total about less than 40s and the brake fluid drops after the pump stops. When the pump is running I can feel it vibrates on the brake pedal.
 
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Nov 11, 2007
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What you describe just above in pumping/priming the brakes suggests normal operation of the booster. However, your initial indication of repetitive booster activations after several brake presses leads me to suspect a marginally performing accumulator (the shiny [or rusty] can shaped thing). It is where the brake booster pressure/energy is stored. When it completely fails, the pressure never builds or remains at proper level. When the accumulator is marginal or is starting to fail, it just won't hold the pressure for long periods and the booster must cycle periodically.

If you have access to another LC accumulator, you could swap temporarily and verify. It's a relatively easy swap (especially compared to a booster assembly install).

Detecting the booster activated also sounds normal to me. It is neither silent nor without vibration/feedback.
 
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St. Louis, Missouri
Hello guys I have a pretty different issue with my brake booster on my 06 lx470. The pump comes on about every 5-6 brake presses during normal driving, and I can feel it vibrating through the brake pedal when the pump is running. But no codes, I am sure you are not supposed to feel or hear the pump running right?
What you describe matches my experience for "normal" operation. As others have noted, you will hear the pump and feel the vibration of the pump through the pedal.

I would estimate that, during normal driving, my pump will run for three to five seconds every 5 to 6 "long" presses of the brake pedal (i.e. coming to a stop). The accumulator maintains pressure in the system, so when it drops below a certain threshold (I would estimate, 70 to 80% of the max pressure), it kicks on to top up the pressure.

Your run-time test seems ok. You might have some residual air in the system, which will both extend your "pressure-up" run time and cause the system to lose pressure faster (air is compressible, hydraulic fluid is not). So, you might try to bleed the brakes (a full flush is recommended if you haven't done that in a while).
 
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Sounds OK. Check the level as instructed on cap and consider servicing the fluid. Toyota can do it for a decent price.
 
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Indiana
Thank you everyone for the reply, I will do full brake flush including the abs module. But it still puzzles me why the vibration can be felt through the motor, I have 05 gx470 it did not vibrate when the pump is running, and I ask my friend who has a 10 4runner he can not feel it either. I also think there is still air in the system, which makes the pump works harder, if there is no air, it can work not as hard, so that reduce the vibration.
 

JunkCrzr89

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Hello guys I have a pretty different issue with my brake booster on my 06 lx470. The pump comes on about every 5-6 brake presses during normal driving, and I can feel it vibrating through the brake pedal when the pump is running. But no codes, I am sure you are not supposed to feel or hear the pump running right?
Sounds normal.
 
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Sep 9, 2016
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Odessa/Midland TX
If the pump runs for 40 seconds, then I'd say it is too much. A brand new unit I installed few months ago, runs about 25 seconds and hardly comes on for next 5-10 minutes.

the issue you are having is the accumulator filed with N2 is leaking so the motor has to run constantly to replenish the loss pressure. If this continues, the commutator on the motor will wear out. If you plan to install a new pump, then save some funds for it, if not, you might see an improvement by just installing a new accumulator, which can be done without pulling the entire brake master assembly out.
 
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Indiana
If the pump runs for 40 seconds, then I'd say it is too much. A brand new unit I installed few months ago, runs about 25 seconds and hardly comes on for next 5-10 minutes.

the issue you are having is the accumulator filed with N2 is leaking so the motor has to run constantly to replenish the loss pressure. If this continues, the commutator on the motor will wear out. If you plan to install a new pump, then save some funds for it, if not, you might see an improvement by just installing a new accumulator, which can be done without pulling the entire brake master assembly out.
That is my initial thought, replce the accumulator seems just need to release the pressure from it and just remove it from the top. And just to confirm that when your pump is running you can not feel the vibration through the brake pedal right?
 
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That is my initial thought, replce the accumulator seems just need to release the pressure from it and just remove it from the top. And just to confirm that when your pump is running you can not feel the vibration through the brake pedal right?
I really don't recall a significant vibration on the paddle with the old brake master pump or the newer pump: I can hear it is running but no vibrations.

How many miles on the vehicle? If you are close to 250 K, I'd say get an entire new assembly. I installed it by my self and it works!
 

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