BRAKE BOOSTER ABS/MODULATOR NOISE

When mine started running like yours is running right now that's what was happening My ABS actuator which is the pump and the reservoir or whatever it's on one brick right behind your inverter mine failed but yet my brakes worked regular for a long time with all the lights on but that noise you're talking about I had it exactly the same times and for the same lengths if not a little longer as soon as I change that actuator all that went away vanished and I expected it to.

 

Yeah, you basically monitor how often that pump runs and once it runs too often you replace the pump. But I think you might have a different problem because if it was the brake pump running that often you'd have warning lights. So suspect the noise you're hearing is something else? Maybe the three-way heater valve? That sounds like an old computer disc drive when it fails, which is kinda like chattering?

 

Sometimes people decide to live with a deteriorating actuator until it is far enough gone.

So how do you judge what's far enough gone?

The pump takes 2 to 4 seconds to rebuild the pressure. That's not too different from a new one.

Your pressure is taking 10 to 15 seconds to leak down so far that the pump has to run again. The corresponding period for a good Prius actuator, while you're not using the brakes, is hours.

So that's how you judge what's far enough gone.

 

No I don't think it would be for the sake of an o-ring The one the valve start leaking internally in that big aluminum block however they got them in there whatever they did I don't know but I wouldn't imagine it would be an o-ring be great if it was there was a guy on eBay that I bought two of these bad boys from that had a rig and said he could rebuild them He sent me pictures of his setup in the shop I paid for one unit and told him that I had two cars with the problem and blah blah blah. This dude sent me another one for free and said well here you go try these and let me know how they go I didn't know if he just started this adventure or what was going on. I put these things in my shop they sat there for months. Then I finally decided to change the one in my '09 because it was time put it on and it works flawlessly I have the other one sitting here in the '05 car that was going to get it is no longer so I have an extra I guess

 

I had the same issue with the pump running as the original post. Brake pump runs for a few seconds every 15 or 20 seconds, both when driving and when the driver's door opens. (after an initial 30 second run) I could also hear a hissing sound from the engine. No codes or dash lights indicated an issue. After reading various posts, it seemed to be the accumulator. The tech at the dealer confirmed the problem for their diagnostic fee of $140.

I ended up having the dealer replace the brake actuator which solved the issue. Now the pump runs infrequently and there is no hissing sound. Presumably the hissing is the brake accumulator (which is part of the actuator unit in a Gen 2) leaking pressure. There were no obvious problems with the braking performance, just the motor noise. After the repair the motor is more quiet when it runs. Parts were $1776 (msrp) and about $1000 in labor including bleeding the brakes. The new part is available online from dealers for roughly $1100 if you do it yourself.

2006-2009 Toyota Prius - Modulator Valve - Toyota (44500-47141)

google the part, I can't post a link. (I'm too new) but check to make sure it fits.


I called two dealers in the area around Baltimore to get estimates. Both quoted the same part price but one wanted to also change the brake master cylinder for an additional $500. I went with just replacing the actuator. Hope that helps. I've had this Gen 2 for 15 years and 238,000 miles and counting.

 

I bought a used remanufactured whatever from a dude off eBay for $300 and I told them what I was doing and he sent me an extra one in case the first one didn't work right so I got two for 300 bucks probably overpaid but the guy was real nice and sent a picture of his test rig and all kinds of nonsense then after I installed one and it worked I was trying to find him to pay him for the other one I can't find them anywhere Nice guy

 

can you post a link or seller name for tested abs units ? That would be helpful when replacing them.

 

He's lost touch with 'his guy' so you might be out of luck.

Tom was the only guy I have seen post such a source.

New units are available from Toyota for ~US$1140 if you shop around the online parts desk like at Camelback Toyota or Olathe Toyota.

The other option would be to try your luck and pull a used one from a wreck or try a junkyard.

 

In SE USA it's VERY common to see 75K to 120K nice conditions PRII with a light hit in car totaled. In other words came out of garage got tapped enroute to Mall walking etc by retirees etc . This is their chance to get a Pacifica or ioniq5. And usually their gonna take that route. Theyres ya perfect parts car. I go to retirement communities and leave notes on them . I get lots of return calls too. Retirees are fair folks . Many retired Military like me so yworks out real well . Especially at Military retirement communities like Danberry Corp.