Brake Pedal Sticky and Slow

Take a look underneath the brake pedal and see why it's sticking

 

Sounds like pedal stroke simulator is bad. It's designed to simulate the pedal feel of a regular brake system. Not familiar with this device as can't remember anyone with that complaint in the last 10 years.

 

Sounds like the pedal stroke simulator. Use the search forum found at top of page and search

Pedal stroke simulator

 

congrats! so the leaking brake actuator made the pedal sticky? i'll never remember that.

 

@psychprof did you figure anything out? I am having the same problem with my 2004 Prius brake pedal.

 

I have a 2007 and have the same issue, and have followed the same path! Replaced the brake booster and no joy. I would really appreciate guidance on this.

 

In Gen 2, the master cylinder is a separate component, and it is not very expensive, and it is the piece on the firewall that the brake pedal directly actuates. It would be worth a look.

If that's not it, the Gen 2 stroke simulator, also mentioned above, is another separate component that could be a suspect.

In this drawing, the master cylinder has callout 47200, and the stroke simulator is callout 47207A.

 

OK I see, TY for the quick reply ChapmanF. TY for the diagram!

As advanced as the Gen2 is, there are no codes related to this, so it is difficult to solve. Today I put the car on jack stands and had a helper put the car in drive with the tires spinning freely. I would callout "brake" then "release". The rear wheels had a slight free wheeling delay. I think they are OK. The front has a noticeable, longer rotation delay when under power and the brake is released. I am suspecting something mundane like a front flexible brake line that has internal blockage. Or a sticky caliper.

This test seemed like a good idea, the rear wheels are free wheeling so I trust they are not the problem. But the front wheels are interlocked thru the tranny so if the left side is the one with delayed release it will feel about the same on the right and act like it has a delayed release.

 

Good morning edthefox5, since your comment in this thread in 2017 have you encountered delayed break release as described here? I searched your suggestion in the forum and did not find anything clear enough to replace either the stroke simulator of master cylinder as ChapmanF suggests.

 

If I understand your time line when it started it had a companion buzzing sound also which is the abs failure alarm along with stiff pedal.

If so my wag would be the actuator that was replaced is defective somehow but not bad enough to launch a abs failure. New actuator should not have a stiff pedal.

Or it was not bled correctly but that should throw a cel.

answer this……with car off just press the brake pedal firmly a few times and let off.
Does that turn on the brake booster pump the one that sounds like a rattlesnake for a few seconds?

 

The symptom of a brake pedal being slow/balky to return is kind of distinctive; it doesn't sound like it would go with a lot of the common brake system ailment stories that get swapped around here.

This diagram in the New Car Features manual shows the master cylinder containing return springs of its own (they usually do).



I think I'd probably first want to see just how balky/sticky that master cylinder by itself is. That could entail undoing the hydraulic connections to it, so it isn't coupled hydraulically to other things in the system, like the stroke simulator. Then it would be a pretty simple test of how it feels pushing in on the pedal and letting it back.

Be aware that any time you undo hydraulics under the hood like that, you will later have to be able to bleed the system thoroughly, which will mean having Techstream on a laptop, or one of the more advanced other tools listed here that are able to initiate the brake bleed procedures.

If the master cylinder seems perfectly well-behaved on its own, I might next wonder about the stroke simulator; that's the other thing mainly there to produce the pedal feel that you experience as the driver.

The other components more or less use the pressure you generate in the stroke simulator as an input, and control valves to operate the real brakes accordingly.

 

I was so afraid of the actuator going and dropping alot of $$$ on it after the new $1600 battery and had seen so many failures on this site I ended up selling my Prius.

It was time. I miss it though. It was a great little pickup and had a tow hitch. You could bring anything home with it.

 

Car off, pushed brake pedal down for 3 seconds and the 2nd time it buzzed, it buzzed again the 4th time.

 

Today the weather was cooler, mid 70's to low 80's. The delayed brake release was less frequent.

 

I think if it’s buzzing it’s also throwing a code. Harvest that code again.

 

C1231 - Steering Angle sensor. The dash says VSC, I think this is unrelated.

No brake codes Ed