Brakes failing randomly

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Hello everyone, I am having a problem with my 2005 Honda Civic's brakes. About a month ago I pressed the brake pedal and the car wasn't stopping, so I released the pedal and pressed it again and the brakes worked fine. I wasn't sure what happened, so I drove very carefully in case it happened again and I was ready to downshift and use the emergency brake to stop if I had to. The brakes felt perfectly fine for several weeks after that happened until yesterday when the same thing happened again. I hit the brake and the car wasn't slowing down, if I remember correctly I released it and pressed it again, still nothing, but it worked fine the 3rd time and has been working fine ever since. When the brakes fail the pedal still feels firm, if anything maybe a little firmer than normal, it didn't go tho the floor.

Here's a list of the changes I made to the brake system:
Rear disc brakes from Civic SI
Proportioning valve for rear discs from the same Civic SI
Steel braided brake lines
Hawk HPS pads front and rear

Other than that the brake system is stock (no ABS). I am thinking after 254K miles the master cylinder may be going out, but I would think that a bad master cylinder would be consistent, it's weird that the problem would be this intermittent. Could the proportioning valve possibly do this?

Thank you very much in advance, I really appreciate your help
 
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Had this happen and the rubber in the master cylinder was getting hard. If you pressed slowly they would not engage. Press faster and they worked. Rebuilt MC and problem fixed, of course after 2 crap MC that leaked first.

Rod
 
If the power assist fails, the brakes still work but you'll have to press really hard on the pedal.

Most other problems will cause the pedal to go to the floor.
 
When it's "not slowing down", does the pedal go to the floor?

Or is the pedal in the normal position, but just not stopping without very hard pressure on it?
 
Thank you to everyone who responded. To clarify, from what I remember the pedal felt relatively normal, it didn't sink to the floor or feel soft. It might have felt a little hard if anything. It didn't feel hard like when the brake booster hose is disconnected though. Could a master cylinder, proportioning valve, and/or booster fail in such an intermittent way like this? Thanks
 
It sounds like a brake booster losing vacuum. Was it cold outside ? Our Mazda2 has done this a couple of times when really cold. The brake pedal goes hard, and the brakes work poorly unless you REALLY stomp on the pedal. Only lasts a minute or so, so something is leaking vacuum.
 
Originally Posted by geeman789
It sounds like a brake booster losing vacuum. Was it cold outside ? Our Mazda2 has done this a couple of times when really cold. The brake pedal goes hard, and the brakes work poorly unless you REALLY stomp on the pedal. Only lasts a minute or so, so something is leaking vacuum.

Thanks. I suppose it's possible that the booster is losing vacuum if the check valve is sticking or something. It wasn't that cold outside when this happened. Last time this happened it was probably around 40 degrees F, the time before that I don't remember but certainly above freezing. This car has seen -20 degrees F when I was in Chicago and the brakes still always worked correctly.
 
Originally Posted by Avery4
Thank you to everyone who responded. To clarify, from what I remember the pedal felt relatively normal, it didn't sink to the floor or feel soft. It might have felt a little hard if anything. It didn't feel hard like when the brake booster hose is disconnected though. Could a master cylinder, proportioning valve, and/or booster fail in such an intermittent way like this? Thanks


Just brainstorming. So the car originally had drums in the rear, and you're still running that master cylinder? I think the master is usually different in a 4wdb car vs. drum rear car. Usually it's just the size of the rear reservoir though, but I could be wrong about that in this application.

The proportioning valve is just a mechanical device, so I don't think those fail. As long as it's the right application, it shouldn't be the culprit.

Maybe there's still air in the system...
confused2.gif
 
Originally Posted by MarkM66
Originally Posted by Avery4
Thank you to everyone who responded. To clarify, from what I remember the pedal felt relatively normal, it didn't sink to the floor or feel soft. It might have felt a little hard if anything. It didn't feel hard like when the brake booster hose is disconnected though. Could a master cylinder, proportioning valve, and/or booster fail in such an intermittent way like this? Thanks


Just brainstorming. So the car originally had drums in the rear, and you're still running that master cylinder? I think the master is usually different in a 4wdb car vs. drum rear car. Usually it's just the size of the rear reservoir though, but I could be wrong about that in this application.

The proportioning valve is just a mechanical device, so I don't think those fail. As long as it's the right application, it shouldn't be the culprit.

Maybe there's still air in the system...
confused2.gif


It came with rear drums, I converted to discs from a Civic SI. I also installed the proportioning valve from the same car so the pressures are correct. Lots of debate about whether this is required, but I changed it to be safe. I didn't change the master cylinder, although I have heard that the master cylinder is different for disc brakes and should be installed with the rear discs for the best performance of the braking system. Not sure if that's true. However, that shouldn't be my problem since this setup has been working perfectly for the last 2 years. If I replace the master cylinder I may as well get one for a Civic SI though.
 
test the servo by starting the engine with the pedal depressed - you should feel it sink. if not, replace it.
bleed every corner PROPERLY and check for leaks while youre down there.
use an obd2 reader to check for ABS codes
check pads and slider pins move freely
check shoes are properly adjusted and drums not lipped.

after that look at the pedal box and linkage to the servo/MC
 
If there's no ABS module to get in the way, these brakes are very simple. My gut is saying the booster is shot, such as the valve that lets in atmosphere into the drum as pedal pressure is applied. It's under vacuum the entire time until the pedal is pressed, which allows atmospheric air in to pressurize one side of it.

Or there is a physical obstruction?
 
Originally Posted by MarkM66
Originally Posted by Avery4
Thank you to everyone who responded. To clarify, from what I remember the pedal felt relatively normal, it didn't sink to the floor or feel soft. It might have felt a little hard if anything. It didn't feel hard like when the brake booster hose is disconnected though. Could a master cylinder, proportioning valve, and/or booster fail in such an intermittent way like this? Thanks


Just brainstorming. So the car originally had drums in the rear, and you're still running that master cylinder? I think the master is usually different in a 4wdb car vs. drum rear car. Usually it's just the size of the rear reservoir though, but I could be wrong about that in this application.

The proportioning valve is just a mechanical device, so I don't think those fail. As long as it's the right application, it shouldn't be the culprit.

Maybe there's still air in the system...
confused2.gif



This This This
 
He has been running the car this way 2 years without problems.

Quote
since this setup has been working perfectly for the last 2 years.
 
Originally Posted by Avery4
Hello everyone, I am having a problem with my 2005 Honda Civic's brakes. About a month ago I pressed the brake pedal and the car wasn't stopping, so I released the pedal and pressed it again and the brakes worked fine. I wasn't sure what happened, so I drove very carefully in case it happened again and I was ready to downshift and use the emergency brake to stop if I had to. The brakes felt perfectly fine for several weeks after that happened until yesterday when the same thing happened again. I hit the brake and the car wasn't slowing down, if I remember correctly I released it and pressed it again, still nothing, but it worked fine the 3rd time and has been working fine ever since. When the brakes fail the pedal still feels firm, if anything maybe a little firmer than normal, it didn't go tho the floor.

Here's a list of the changes I made to the brake system:
Rear disc brakes from Civic SI
Proportioning valve for rear discs from the same Civic SI
Steel braided brake lines
Hawk HPS pads front and rear

Other than that the brake system is stock (no ABS). I am thinking after 254K miles the master cylinder may be going out, but I would think that a bad master cylinder would be consistent, it's weird that the problem would be this intermittent. Could the proportioning valve possibly do this?

Thank you very much in advance, I really appreciate your help


Yep , I would check the master cylinder & brake booster also , first .
 
Originally Posted by WyrTwister
Originally Posted by Avery4
Hello everyone, I am having a problem with my 2005 Honda Civic's brakes. About a month ago I pressed the brake pedal and the car wasn't stopping, so I released the pedal and pressed it again and the brakes worked fine. I wasn't sure what happened, so I drove very carefully in case it happened again and I was ready to downshift and use the emergency brake to stop if I had to. The brakes felt perfectly fine for several weeks after that happened until yesterday when the same thing happened again. I hit the brake and the car wasn't slowing down, if I remember correctly I released it and pressed it again, still nothing, but it worked fine the 3rd time and has been working fine ever since. When the brakes fail the pedal still feels firm, if anything maybe a little firmer than normal, it didn't go tho the floor.

Here's a list of the changes I made to the brake system:
Rear disc brakes from Civic SI
Proportioning valve for rear discs from the same Civic SI
Steel braided brake lines
Hawk HPS pads front and rear

Other than that the brake system is stock (no ABS). I am thinking after 254K miles the master cylinder may be going out, but I would think that a bad master cylinder would be consistent, it's weird that the problem would be this intermittent. Could the proportioning valve possibly do this?

Thank you very much in advance, I really appreciate your help


Yep , I would check the master cylinder & brake booster also , first .

Thanks. How do I know which is bad when the problem is so intermittent? I can do all the typical tests that I know of (hold the pedal to see if it sinks, pump the brake pedal after the car sits to make sure it still has assist, etc) and everything tests good and the brakes work fine until they suddenly don't, it's weird how intermittent this problem is. I'm thinking booster though because if the master cylinder was bad I would think the pedal would be soft and sinking to the floor. I'm not a parts changer, but I may just change both the booster and master cylinder depending on how much I can get them for. After 254K miles they are probably both worn out and I would feel better knowing that both parts that can cause this are new and I would rather do this once, easier to change them both together.

What brands would you suggest (Or stay away from) for the master cylinder and booster?
 
Originally Posted by Trav
Just disconnect the hose to the booster if you can blow air through by mouth it its defect. It is a one way check valve meaning it only works with the draw of a vacuum.
This explains how to test the booster itself with a hand held vacuum pump.

https://gpsbrakes.wordpress.com/category/how-do-i-test-my-vacuum-power-brake-booster/

Thanks. On my car the check valve is actually in the brake booster's hose rather than the booster itself and it is good, I took the hose off and blew back and forth several times and it worked correctly. I can let the car sit overnight and still have enough vacuum for a couple of pumps in the morning. From my understanding the only purpose of the check valve is to maintain vacuum in the booster if the engine stalls so the driver can safely stop the car, so the only way the check valve could cause the brakes to fail like this is if it is sticking closed and not allowing flow through the hose.
 
For the master cylinder , first look for leaks . If it feels " spongy " , it is bad . Other than that , not sure .

Brake booster , listen for leaks . Disconnect & plug the vacuum hose . Any difference in the way the brakes work / perform .

I am with you , with the miles on the vehicle , I would replace both , if in doubt . Check out rockauto.com . Other than OEM , I do not know which brand to avoid vs. purchase .

Best of luck to you .
 
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