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