Brake assist priming occuring every 15 seconds or so
 

Hi All,

I have a '07 TCH with 109k miles on it.

I recently noticed that when I open the car door to get into the car (with the engine off), the brake assist primes for quite a bit (> 30 seconds). Searching my brain, I recall in the earlier days it would only prime for about 5 seconds).

When I start my car, I notice that the sound can be heard priming the brake (vacuum?) every 15 seconds or so and lasting about 3-5 seconds. It primes every time I release the brake pedal.

No errors are shown on the dash board. I suspect the vacuum tank (if there is one) is leaking, causing it to prime often.

Has anyone had this problem? I am out of warranty and dreading to see what the damage is when I take it to the dealer. I'm hoping it's just a loose screw :)


My apologies if this has been discussed before. I tried searching the forums and couldn't find any relevant threads (could also be because I'm not using the proper search terms).

Re: Brake assist priming occuring every 15 seconds or so
 

That's your brake actuator or accumulator, there's no brake booster (or vacuum in conventional cars) if there are no VSC errors showing up on the dash I guess it's still ok. It might be leaking a little bit (which is a common issue on prius) Others tried to bleed the brakes hoping it will fix the problem. Is the noise louder or just the same but longer?

Re: Brake assist priming occuring every 15 seconds or so
 

Thank you for your reply. The sounds is the same audible level as before. It does get a tad bit louder as it nears the end of the cycle.

What does the accumulator / actuator do? It sounds like an electric pump going on and off.

Re: Brake assist priming occuring every 15 seconds or so
 

it controls the hydraulics (along with the skid control ECU) of your brakes which consists of pump motor, linear solenoid valve, accumulator, wheel cylinder and master cylinder pressure sensors.

Re: Brake assist priming occuring every 15 seconds or so
 

I have exactly the same problem, Toyota says the brake actuator must be replaced, the situation will eventually lead to a brake pump failure, and it is as if you are pressing the brakes every 15 seconds. I suspect the cause is an internal leakage and/or fault in the overpressure relieve valve inside the actuator unit. You can hear this leakage as a hissing noise inside the actuator after priming. Unfortunately the actuator is a sealed unit with pressurized nitrogen and cannot be opened or serviced, this means around $2k or so to solve the issue.:angry:

Re: Brake assist priming occuring every 15 seconds or so
 

I hear you there. My actuator/accumulator would turn on every 5 seconds and I determined it was time to get it fixed. I did not want the actuator failing on the road leaving me without brakes.

When I called my toyota parts store (Frontier Toyota in Santa Clarita, CA), to see how much the part is, the parts mgr. asked me if I got their number online. I did and he initially quoted me $1252. Then he said it would be around $150 to ship. When I told him I was local, he then changed the quote to $1669 (the MSRP). When I asked him about the lower price, he said they had a different website to compete with online retailers, but since I was a local, he could not give it to me for that price.

Long story short, I found the other website he was talking about: http://www.mytoyotapartsstore.com/in...brake+actuator and printed it out and made sure to include the page that stated

"MyToyotaPartsStore.com is the parts department of Frontier Toyota a full service Toyota dealership located in Valencia California."

The service advisor was able to give me that price (without the shipping charge), so total out the door to replace my brake actuator was $1655.63. Here's what they did:

REPLACED ABS ACTUATOR ECU ASSY. AND BLED BRAKING SYSTEM.

PERFORM MULTI-POINT INSPECTION (FREE) FRONT BRAKES _8MM___ REAR BRAKES_4.5MM_____ TIRE PSI32________

CUSTOMER STATES INSPECT BRAKE ACTUATOR MAKING LOUD BUZZING NOISE/INSPECT AND ADVISE. NOISE WAS VERIFY BY SHOPFORMAN IT WAS ALSO VERIFY BY TECH SEEM LIKE BK ACTUATOR ITS DICHARING BY ITSELF.AS 1ST SPEP WILL BE R/R ACTUTOR AND BLEED SYST , NO EXTERNAL BK FLUID LEAK.

On a side note, after 110k miles it's almost time to replace my rear brake pads. This will be the first time since I bought the car it will be done. The front pads are still in good shape.

Good luck! At the very least, you could buy the part and have your dealer install it and save about a hundred bucks or so.

Re: Brake assist priming occuring every 15 seconds or so
 

I'm confused. Is there supposed to be a noise? How often should you hear the noise? I hear mine rather consistently when starting the car, baking, and when I shut the car off. If it is a problem I'd like to get it fixed before the extended warranty is up.

Re: Brake assist priming occuring every 15 seconds or so
 

This seriously bugs me. I just bought a 2007 Camry with 30K and is still under the 60K powertrain warranty until July 2012 but to hear of such premature failure of a brake system is absurd! Where is the Toyota quality that I paid premium for?? Now they expect us to fork out $3000.00 to replace this unit?

I've been a proud owner of many Toyotas in the past but now I'm really questioning why??

So who wants to join ranks and bring this up to Toyota??? I'm sure we can gather many Prius owners who are forking out money to repair this "brake accumulator" issue. How about those whose emptied their pockets to patch the issue? Wouldn't you like some compensation??

I'd like to get something done about this but need your help to figure out where to begin.

Re: Brake assist priming occuring every 15 seconds or so
 

I guess the fist step would be to figure out what "normal operation" is. I haven't' found anything clear on that yet. I'm going to search alldata and see if I can find anything. Maybe someone that knows how this system is "supposed" to work can chime in.

Re: Brake assist priming occuring every 15 seconds or so
 

Well. As far as I understand from other members, the a slow leak will cause the accumulator to pump more frequently and eventually throwing codes and then eventually complete loss of brake pressure altogether.