Brakes Stopped Working Unexpectedly While Driving
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Brakes Stopped Working Unexpectedly While Driving
I'm having brake issues with my 2005 Civic EX. I bought the car a few months ago and, periodically since I bought it, I have gotten into the car while it was off and the brake pedal was rock hard and wouldn't depress at all. When I turn on the car in these cases, the brake pedal goes down and the brakes work just fine. Today, on the drive home from work I went to brake to take a turn and the pedal was rock hard again. I pressed really hard and the car braked somewhat, enough so I could slow down to make the turn. The car skidded like the brakes or the wheels or something had locked up. I was driving over some very light snow at the time and I still have summer tires on it, so I don't know if the slickness had anything to do with it. Could this have been some sort of response to the slickness? What could be wrong and what should I do? The whole thing was quite scary!
Last edited by RyanHostetler; Dec 2, 2016 at 08:10 PM.
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Re: Brakes Stopped Working Unexpectedly While Driving
The brake booster operates using engine vacuum.
There is a check valve in the vacuum hose between the engine and the booster.
When the engine is running (idling) there is supposed to be plenty of vacuum present to keep the brake booster operating.
When you shut the engine off, the booster should have enough vacuum stored in its chamber to provide power assist for a minimum of at least one, and usually two brake pedal applications before stored vacuum is exhausted and assist ends (manual braking is still available as always, but the pedal is hard to push).
IF you shut off the engine and inadvertently push the brake pedal as you exit the car, that may explain why the pedal is hard the next time you get in the car and before you start the engine.
IF the vacuum check valve leaks overnight, that would also explain a hard brake pedal the next morning.
IF your area is near or below freezing temperatures, the vacuum check valve could freeze in the open or closed position, which would cause problems with the assist (due to wild variations in the amount of vacuum available for booster assist)
In this case I'd replace the vacuum hose assembly that runs from the brake booster to the intake manifold.
If you have an EX, I would have expected the ABS to kick in and grunt a lot as you tried to skid on snow. Unless it's got problems too.
There is a check valve in the vacuum hose between the engine and the booster.
When the engine is running (idling) there is supposed to be plenty of vacuum present to keep the brake booster operating.
When you shut the engine off, the booster should have enough vacuum stored in its chamber to provide power assist for a minimum of at least one, and usually two brake pedal applications before stored vacuum is exhausted and assist ends (manual braking is still available as always, but the pedal is hard to push).
IF you shut off the engine and inadvertently push the brake pedal as you exit the car, that may explain why the pedal is hard the next time you get in the car and before you start the engine.
IF the vacuum check valve leaks overnight, that would also explain a hard brake pedal the next morning.
IF your area is near or below freezing temperatures, the vacuum check valve could freeze in the open or closed position, which would cause problems with the assist (due to wild variations in the amount of vacuum available for booster assist)
In this case I'd replace the vacuum hose assembly that runs from the brake booster to the intake manifold.
If you have an EX, I would have expected the ABS to kick in and grunt a lot as you tried to skid on snow. Unless it's got problems too.
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The brake booster operates using engine vacuum.
There is a check valve in the vacuum hose between the engine and the booster.
When the engine is running (idling) there is supposed to be plenty of vacuum present to keep the brake booster operating.
When you shut the engine off, the booster should have enough vacuum stored in its chamber to provide power assist for a minimum of at least one, and usually two brake pedal applications before stored vacuum is exhausted and assist ends (manual braking is still available as always, but the pedal is hard to push).
IF you shut off the engine and inadvertently push the brake pedal as you exit the car, that may explain why the pedal is hard the next time you get in the car and before you start the engine.
IF the vacuum check valve leaks overnight, that would also explain a hard brake pedal the next morning.
IF your area is near or below freezing temperatures, the vacuum check valve could freeze in the open or closed position, which would cause problems with the assist (due to wild variations in the amount of vacuum available for booster assist)
In this case I'd replace the vacuum hose assembly that runs from the brake booster to the intake manifold.
If you have an EX, I would have expected the ABS to kick in and grunt a lot as you tried to skid on snow. Unless it's got problems too.
There is a check valve in the vacuum hose between the engine and the booster.
When the engine is running (idling) there is supposed to be plenty of vacuum present to keep the brake booster operating.
When you shut the engine off, the booster should have enough vacuum stored in its chamber to provide power assist for a minimum of at least one, and usually two brake pedal applications before stored vacuum is exhausted and assist ends (manual braking is still available as always, but the pedal is hard to push).
IF you shut off the engine and inadvertently push the brake pedal as you exit the car, that may explain why the pedal is hard the next time you get in the car and before you start the engine.
IF the vacuum check valve leaks overnight, that would also explain a hard brake pedal the next morning.
IF your area is near or below freezing temperatures, the vacuum check valve could freeze in the open or closed position, which would cause problems with the assist (due to wild variations in the amount of vacuum available for booster assist)
In this case I'd replace the vacuum hose assembly that runs from the brake booster to the intake manifold.
If you have an EX, I would have expected the ABS to kick in and grunt a lot as you tried to skid on snow. Unless it's got problems too.
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Hmm. I'm not sure whether the ABS kicked on or not. To be honest with you, I've never thought a lot about what ABS is or what it does. As far as it making a sound or not, I cannot say for certain because I was listening to very loud music at the time. Is there another symptom of the ABS kicking in besides it making a grunt?
You need to experience what ABS acts like before it surprises you in a panic situation.
When it does its thing you should be able to feel the brake pedal vibrate and move under your foot in addition to the grunt noises. MAYBE that's what you felt. Try it out and see. Take it out and try to make it skid.
HINT: If you feel/hear the ABS doing its thing as you jam the brake pedal and go right through the stop lights, that's your fault for going too fast in the first place.
IF the ABS activation is not what you felt while driving.....then I'd be more concerned with the hard brake pedal and lack of power assist first.
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Well...turn the radio off and try it again.
You need to experience what ABS acts like before it surprises you in a panic situation.
When it does its thing you should be able to feel the brake pedal vibrate and move under your foot in addition to the grunt noises. MAYBE that's what you felt. Try it out and see. Take it out and try to make it skid.
HINT: If you feel/hear the ABS doing its thing as you jam the brake pedal and go right through the stop lights, that's your fault for going too fast in the first place.
IF the ABS activation is not what you felt while driving.....then I'd be more concerned with the hard brake pedal and lack of power assist first.
You need to experience what ABS acts like before it surprises you in a panic situation.
When it does its thing you should be able to feel the brake pedal vibrate and move under your foot in addition to the grunt noises. MAYBE that's what you felt. Try it out and see. Take it out and try to make it skid.
HINT: If you feel/hear the ABS doing its thing as you jam the brake pedal and go right through the stop lights, that's your fault for going too fast in the first place.
IF the ABS activation is not what you felt while driving.....then I'd be more concerned with the hard brake pedal and lack of power assist first.
In regards to the ABS, I'm not an aggressive driver and I don't generally take turns very fast, so I don't think I'm experiencing the ABS on any kind of regular basis. I also live in the inner city and there is currently no snow here (the snow was in another city that I commute to), so I'm going to have a hard time doing the skid test at the moment.
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I just went out to examine my vent problem (separate problem and post that appeared simultaneously)
and, with the car started and idling, the brake pedal is very hard and won't depress except for a very small amount. This hasn't happened before while the car is running. The current temp here is 28 degrees.
I'll guess the check valve is frozen. It happens once in a while especially after they have a bunch of time and miles on them.. I'd replace the vacuum hose (it contains the check valve) between the engine and brake booster. I'd get a Honda dealer part.
In regards to the ABS, I'm not an aggressive driver
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I'll have to give that a shot the next chance I get. I've got snow tires on my other Civic, but I didn't take it because I didn't expect snow today.
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From: Midwest. Aiming about mid-chest
Rep Power: 517 If you think a good mechanic is expensive, try hiring a bad one
Joined: Dec 2011
Posts: 32,017
Likes: 256
From: Midwest. Aiming about mid-chest
Rep Power: 517 If you think a good mechanic is expensive, try hiring a bad one
Joined: Dec 2011
Posts: 32,017
Likes: 256
From: Midwest. Aiming about mid-chest
Rep Power: 517 
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...change your brake fluid and inspect the reservoir lid & seal for cracks. Brake fluid will draw in moisture from the air.
Adding brake fluid from a container that has been left open will put water into the system. So don't think that there couldn't be water in the fluid just because the booster seal isn't worn out.
My theory: The water droplets* floating around in the oil. Water expands while becoming ice, creating pressure in the system.
Adding brake fluid from a container that has been left open will put water into the system. So don't think that there couldn't be water in the fluid just because the booster seal isn't worn out.
My theory: The water droplets* floating around in the oil. Water expands while becoming ice, creating pressure in the system.
