ABS Actuator Replacement - DIY Questions

Did you end up replacing the actuator? If so, how did it go?

The only noise I've ever heard with my brakes is that rattlesnake sound whenever I first enter the car and also every few times I hit the brakes. I've heard this is normal operation for the Prius.

However, recently I've noticed the duration of the rattlesnake snake sound on entry is increasing... Maybe a sign of the actuator slowly going bad?

 

Bleed brakes with Techstream

 

Are you saying that the rattlesnake noise is an indication that the brakes need bleeding? I've been driving with this noise for years.

 

A rattlesnake is what the pump sounds like. The pump is installed in the car on purpose, and the brakes wouldn't work well without it, and every time it runs when it's supposed to, it sounds like a rattlesnake. That's normal.

What's not normal is if it runs more often than it's supposed to.

Normally, you should hear it run for a bit when you open the driver's door, if the car has been parked for a while, and you should hear it run a little every few times you use the brakes. How many is a "few"? That depends on things like how hard you brake, and the state of adjustment of the brake shoes. There's no etched-in-stone number to give you.

If you hear it every single time you brake, that could indicate an incipient problem. If you hear it run by itself, cycling on and off, on and off, on and off, when you are not even touching the brakes, that is a problem already gone way past bad. (It is weird how many people with the pump doing that will still post about it apparently hoping to hear they don't have a problem.)

But just hearing the rattlesnake pump doing its normal job is no problem at all.

Following up an earlier post upthread about bleeding: if the actuator is changed, use Techstream to bleed. There are electrical valves in there that open and close different passages in it, and there is no such thing as any manual bleed procedure that will get the air out of the valved-off parts, without Techstream making the valves open for you.

 

Thanks for the clarification - that is how I understood the pump to function. My main worry is that my pump seems to run longer when I open the front door than I previously recall.

Any reason to consider only a brake bleed if I'm not getting any of the other symptoms you mention? Also, what are your thoughts on this manual bleeding process?

 

There can be perfectly benign reasons for that. The pump is electric, and the car is off when you first open that door, so it is running off the small 12 volt battery in back. If the seasons have changed and the battery output is a bit less in cooler weather, the pump runs more slowly and takes longer. (It can often be the first giveaway if your battery is getting near to replacement time; then the pump will stop sounding like a rattlesnake, and sound more like a dying wind-up toy.)

Generally, the only reason for bleeding the brakes is if you either know, or suspect, that there are bubbles trapped in the system, such as if you have had it open and worked on it. Then you bleed it.

Sometimes people will recommend doing a replacement of old fluid, and some people use the terms "bleeding" and "fluid replacement" as if they were interchangeable, which they aren't. In fluid replacement, you're not trying to get bubbles out, and if you do it right, no bubbles get in. There can be workable "alternative" manual procedures for fluid replacement, even though there aren't for brake bleeding, because if you assume there are no bubbles to start with, then the only downside of the manual procedure is a small amount of old fluid that didn't get changed behind the valves that were closed, and that's not a big problem. If there were air present, that would be a bleeding fail.

Not a good sign that I wrote a bit last February about relying on random youtubes for service advice and that the example I closed with then was, um, that exact video.

In general, you have to decide how reliable the source is. If it is someone who clearly understands the process from the repair manual and exactly why it is specified as it is, and has insights to add on top of that, there could be something to it.

When the person's reason for giving you an "alternative" procedure is that he found the prescribed one "confusing", with "a lot of steps and there's a lot of focus required" ... hard pass.

 

Have been having a heck of a time replacing the brake actuator on my 06 Prius - Have now installed 2 different used actuators and am still getting the same C1256 (Low accumulator pressure) code I started with on the original actuator. Wondering if there might be something I’m overlooking? The install itself seemed to go smooth enough. I bought a Xtool D8 scan tool to do the ABS bleed.. am worried that air may be getting stuck in the actuator - both times I’ve installed a replacement, I hear the actuator running initially, and then after some time it sounds a little choked ( I assumed air was in it) and then I stop hearing it altogether… but despite bleeding the system with scan tool multiple times, I still don’t seem to have any improvement..

Also might be worth mentioning that when I go to open the bleeder on the rear brakes, no fluid comes out?

While I realize that installing a used part is a bit of a gamble, its hard for me to believe that all 3 actuators I have had in the car all have exactly the same problem.. seems there could be something other than the actuator itself causing the code? I also intermittently have seen a C1252 (motor of hydro-booster pump ) code… which I think comes on if the pump runs longer than it should..so maybe this suggests the pump is working and there aren’t issues with the electrical which goes to the pump?

Any help appreciated

 

I know this is an old thread, but has anyone tried just leaving the actuator in and not replacing it. What is the worst that can happen? I have a 05 Prius that isn't worth enough (with 190k miles) for me to buy a new actuator and have a shop replace it. I don't have the expertise and time to do it and don't think putting a used one will be that helpful.

Anyone know the issue with leaving it "as is" and continuing to drive it?

 

The worst that can happen is no brakes for your car, and you are unable to stop before you hit something.

Properly working brakes are VERY important thing to have while driving a car!

What is your life worth to you?

 

There can be several levels of reduced brake function depending on the fault. If the pump inside the actuator completely fails, then there is no high pressure fluid for normal brake operation. No brake boost, no ABS or traction control, no rear brakes. Also I think the hybrid system will disable regen braking.

That leaves the final backup - direct connection from the master cylinder (brake pedal) to the front calipers. This would be "pull the car over and get it towed" mode, as it is very unsafe vs normal braking.

Posted via the PriusChat mobile app.

 

I once checked out a hybrid Camry in facebook marketplace that has a failed actuator, he's trying to sell it because it completely lose the ability to brake and a continuous beeping sound can be heard and all the dash lights are on. I tried driving it within a block and have to hit the parking brake, it was scary (but I got warned) It was easy to replace on hybrid Camry (open space on the passenger side) but not that easy on the Prius (worst on gen3 because of extras) and definitely can't do manual bleed. The Autel MaxAP200 dongle can do the ABS bleeding.

 

It would be nice if Autozone or Amazon sold rebuilt master cylinders for a Prius. But they don't.

A gen2 brake booster/master cylinder is easier than a gen3.

Most of the time the brake warning lights and codes happen before power brakes are lost and your braking still seems normal. You remain in a brake by wire mode but it is taking too long to build up hydraulic pump pressure.

Some who ignore it long enough can have a sudden loss of braking which results in no power brakes and vastly extended stopping distances. Even this mode is dependent on a set of solenoids mechanically moving to a position where brake pedal pressure is connected to the front brakes without power assist.

The unexpected loss of braking power can cause a wreck and involve innocent people who did not have a choice in the matter.

If I were strapped for money I would consider a used actuator and an independent shop to install it. I would skip the rent if necessary. It is serious.

 

There is a small electrical motor inside the abs module that spins to produce brake pressure with the accumulator.

Both the electrical motor and the accumulator can go bad over time. The electronic module itself should be ok.

What happens is this, there's 3 carbon brushes on the electrical motor that wears down and needs to be replaced. You will need to take it to a millwright(he generally works on much larger electrical motors) and ask for his advice on how to replace those brushes(this needs to be properly done, or else it will overheat and cause a short. Ask me how I know). Secondly, the accumulator can also go bad and not hold pressure anymore. You will need to remove that and replace it with a new one. You can try to go up one size or something smaller(whatever is available on ebay). It will probably just run the electric motor more often.

Then you will need to properly bleed and fill it with techstream. Doing it this way is cheaper because if you buy a new module, you're looking at $500+ for old parts that will wear out just the same. So why not just spend that same $500 on new parts? Or, you can buy a new ABS module for $1200 and use it until your car shoots the crap, then remove that ABS module and sell it- that's the most reliable fix but you have to spend more money upfront.

IF you can fix that ABS module, you can still get alot of life out of the car. It is worth lifting weights in this area.

 

IF you can fix these things you should start doing it for a living. Others have tried and failed.

 

I can continue to work out figuring a solution to the small electrical ABS motor because I've already gotten started on it but I would need someone to figure out how to fabricate and repair the accumulator. It is a metal bellows system with gaskets and then filled with a gas.

This needs to be figured out because of tariffs where most of these aftermarket parts come from China.

If anyone wants to fund the research where I can go to the manufacturers and speak to the right folks to see how they make these parts, let me know.

 

What about the leaks inside the actuator?

$1200 for a new one isn't the most expensive car part by quite a stretch.

 

The brake system, especially a complex system like the Prius, which works intelligently, directing energy to the battery or to press the brake pads - this is something I would not interfere with at all. Safety first.
The original spare part in the brake system is my choice.

 

I agree 1200 isn't alot considering how important the part is. But when you tear it down to specific smaller components that needs to be replaced, it then starts to look expensive because those parts are no more than $300. The electric motor, you can just replace the brushings for $20 and still get quite alot of life out of the it. The acummulator you can replace it with a $200 part.

I haven't looked into the leak inside the actuator. Hopefully its not too difficult to deal with.

The ABS module has hard mechanical components that can be replaced with a little finessing. If we are talking smaller parts such as mother boards and chips, the equipment and knowledge to deal with those things are too far fetched.

I think what REALLY sparked my interests into the ABS module was that it immobilized the entire system. I didn't like the fact something that small grounded my vehicle. A bad wheel bearing is easy to understand and replace. But a bad small electric motor is more skew and hidden.

 

the ABS pump motor is not the issue (and they last way longer than the car) It's the leak in the accumulator which requires you to get a replacement since it's not possible to fix it with gaskets or o-rings. I was able to replace ABS failure on other cars like Volvo XC90 by just replacing the ABS pump motor and leaving the electronics/actuators (there will be a DTC for that issue) Prius ABS is not designed similar however.