Emergency brake/parking brake not engaging

probably a disconnected/broken cable. are you the handy type?

 

When is the last brake inspection?

How much brake pad is left on the rears?

 

Proper maintenance on the brakes has been lacking. Someone has neglected the rear brakes. This entails cleaning, lubricating the contact points, checking remaining material thickness, and ADJUSTING the brakes, so the they are the correct distance from the drum which will allow the parking brake to engage properly.

 

If the behavior you are describing is that the pedal does not stay down when you press it, but makes no clicks on the way down and then follows your foot right back up again, then the responses about broken cables or brake adjustment are not on point. What you have is a ratchet at the pedal itself that is not clicking into place and holding the pedal down.

Mine gets very close to doing that in very cold weather, when the grease on the ratchet pawl thickens up and then the pawl doesn't spring quickly into place. Sometimes it will if you just press the pedal down, and hold it there a bit longer, so the thickened-greasy-ratchet-pawl can sloooowly settle into place.

What temperatures are you seeing?

If it's not super cold, it's also possible the ratchet there broke somehow, or the grease has just turned gummy altogether.

 

Hmm, mine doesn't act that way unless it's a lot colder than that. But maybe you also have hotter summer temps there and the grease gets baked faster.

I would try to get access to that ratchet mechanism on the pedal and clean off whatever original grease is there and apply new. I'm not sure how easy the pedal access is without some trim panel and/or dash disassembly ... the repair manual will give some insight.

 

You have had some good replies. It does seem temperature related. Some greases thicken as temperature decreases. If there are no mechanical issues that are causing this problem then cleaning off the old grease and using a lighter weight grease could help.

My 2008 Prius emergency brake works fine and today it was 12 degrees this morning with plenty of moisture/ precip. I wonder if there isn't something else mechanical going on with your ratcheting mechanism or cable? These emergency brake cables will also sometimes have lubricant applied to them that can stiffen with colder temps.

 

Typically the parking brake is actuated mechanically by the parking brake pedal and cable system. This can be applied with the car completely off or with the car on.

Your assumption that it is independent of the brake actuator system is correct. Emergency/parking brake is a completely mechanical system that does not use the brake actuator.

One quick suggestion is to disconnect the cable from the parking brake pedal /actuator assembly then push the parking brake pedal and see how it responds, this may help you isolate the problem without having to go underneath the car or open up the rear brakes

 

You really should use your parking brake on a regular basis, at least once a week. The rear drums have a self adjuster that basically turns the screw on the bottom of the brake shoes to make them be as close to the drums as possible. When you don’t use the parking brake this never gets adjusted as the parking brake is how the adjuster works.

 

The story you're telling here is exactly the story of a sluggishly-moving ratchet pawl right up in the pedal mechanism.

There are other things that can go wrong with brakes (sticky cables, etc.), but they would give you different stories, which are not the one you're telling here. (If you had a story about the pedal being hard to press down, or staying stuck down after you release it, or rising back up only part way, that would be a sticking-cable story, for example.)

It will, but you can't hurry it by just stomping the parking brake a bunch of times.

Each time you apply the parking brake, if there is more than the correct clearance between the shoes and the drum, a lever in each rear brake will be lifted up over a starwheel tooth and click down behind the next tooth.

The next time you stop using the regular brake, the shoes being expanded by the regular brake will take the return-spring pressure briefly off that starwheel adjuster, allowing the adjust lever to turn it by that one notch, and adjusting 0.03 mm out of the brake clearance.

That will keep happening, 0.03 mm at a time, until the clearances are within tolerance.

If they are badly out of adjustment, there's a rubber plug in the backing plate that can be removed so a screwdriver can be poked in to turn the starwheel by hand a few teeth at a time. Don't overdo it or the brakes will drag.

 

I think you should use the parking brake daily instead of annually.