Brake failure question

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grumpyoldman

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I recently gave my '98 Civic with 202k miles to my girlfriend's 16 year old daughter to learn how to drive & drive stick. The other day the brakes failed--pushed the pedal to the floor/almost to the floor to get any stopping power at all. My GF took over, verified the braking problems, then limped it home at low speed using the hand brake to stop. A few days later she had it towed to the local shop. They couldn't find any problems--brakes worked fine on their test drive, no leaks found, pads inspected & found to have plenty of life left. She drove it home without problems.

Other facts:
- Hot day
- No riding the brakes or other repeated hard braking, I think
- I flushed & replaced the fluid zero times in 18 years (flame away; I deserve it)
- Never had any brake fade in all the years I drove it
- No recent brake work. Last work was me replacing the front pads @ 184k about 2.5 yrs ago

They live in a different city, so I haven't been able to do any testing on it myself. I recommended having the shop flush & replace the brake fluid, but my main concern is that, without knowing exactly what caused the original problem, even if they do I can't let the kid or anyone else drive it in good conscience. I'm ready to junk the car, but I thought I'd ask BITOG first. Is there anything I can do to verify the problem & fix it? thanks
 
I would replace the master cylinder. Sounds like an intermittent failure, and with 18 years of zero maintenance, not surprising...pedal to the floor is a leak, either external (which you said wasn't the case) or internal to the master.
 
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I would just go through and look at the entire brake system. It is a civic so it has plenty of life left in it. I would replace the Brake Master cylinder and check the Brake pads/rotors. Going to the floor either means a leak or a large air bubble in the system which would represent a leak. I would also probably replace the rubber brake hoses.
 
The first two things I'd check are the master cylinder and the rubber sections of the brake lines. If it's hot out and one or more has a weak spot it could cause a similar issue.

But then, if a shop weren't able to find the issue I'd first find a different shop.
 
Originally Posted By: Astro14
I would replace the master cylinder. Sounds like an intermittent failure, and with 18 years of zero maintenance, not surprising...pedal to the floor is a leak, either external (which you said wasn't the case) or internal to the master.

This
 
Let's see, a new driver, I think they were riding the brakes. If the brake pedal goes to the floor, that's usually a master cylinder if you can't find any leaks. But it would probably keep doing that. That's why I think it's riding the brake and if you never flushed the fluid, you've got some water in there and it boils quickly.
 
Find another shop there's something wrong with the brakes. I'd say it's probably the master cylinder. It should be easy enough for a good shop to diagnose and fix.
 
Originally Posted By: Wolf359
Let's see, a new driver, I think they were riding the brakes. If the brake pedal goes to the floor, that's usually a master cylinder if you can't find any leaks. But it would probably keep doing that. That's why I think it's riding the brake and if you never flushed the fluid, you've got some water in there and it boils quickly.


This^^
I had a very similar experience with one of our '86 Civics caused by a stuck parking brake cable on the driver's side. I was coming to a red light at the bottom of a long hill at maybe fifty or so and the brake pedal went to the floor. I pumped it once and had brakes, thankfully.
I got home and checked all of the wheels for excessive heat. When I got to the right rear, I knew I'd found the problem. It was unbelievably hot. Turned out that the parking brake cable housing had come loose from the crimped bit that held it and it couldn't retract, thus making those shoes drag.
I freed the shoes with a quick flip of the wrist on the cable and all was well again.
My theory was that the high temperature had caused local boiling of the brake fluid, rendering it a compressible gas, hence no brakes.
If this proves to be the case with your old Civic, great. If not, I don't think it's the master cylinder, since those usually begin to bypass gradually and they don't fix themselves to the point that the brakes then seem normal on a test drive.
 
Interesting theories, Wolf359 & fdcg27. I'll probe further into if she was riding the brake, left the hand brake on, cable was stuck, or got the fluid to boil in some other way. The only times I'd ever heard of brake fluid boiling was at races or track days, under very hard braking. I didn't think of a stuck cable causing a big temperature rise, but your story is proof.

My only experience with a master cylinder failure was on a motorcycle but also matches your story. Brakes were very soft (lever could be pulled almost to the handgrip; pumping helped) & never recovered to the point of seeming normal. I was about to order a new MC when I got the recall notice from the factory. Fixed for free.
 
Originally Posted By: JimPghPA
If it is a vacuum boost system I would also look for a bad vacuum hose.


Thanks Jim. Wouldn't a vacuum failure signature be different, like losing power brakes? Or can it cause the pedal-to-the-floor problem?
 
Nobody ever rides the brakes or brakes hard, just ask them and they will tell you.

Young driver stopping harder than ever before, and more often learning how to drive a stick shift. Bound to boil the water in the 18 year old fluid. Problem "goes away" when it cools down, and the shop probably never drove it hard enough or long enough to get the fluid hot again.

If this were my car, id flush the brake with fresh fluid, use the entire quart, and take it for a drive around the section making repeated 45 to 25 mph "stops" brake for 10 seconds, let cool for 20 (just like bedding new pads). That will get things good and warm without overheating anything.

Bleeding the brakes may cause a leak in the master, but that will show up as spongy brakes all the time.

My thoughts on what I would do in your shoes.

Keep us posted.
 
Replace the brake M/C - " I flushed & replaced the fluid zero times in 18 years (flame away; I deserve it)"It wouldn't hurt the inspect the whole syster due to its age. Brakes are one of the things you shouldn't cut corners on
 
Can anyone explain why they are so quick to throw parts at it?

Has anyone ever had a M/C fail, then heal itself?

Heck, lets just throw new lines, hoses, calipers, and wheel cylinders at it too. Surely the problem lies within those parts somewhere.

This is a case for K.I.S.S. if I ever saw one. This failure mode reeks of a fluid problem, start there. But, for whatever it's worth, a new m/c will likely fix the problem, but only because you'll be flushing the system with new fluid.

I bet if he reused the old fluid, though, the problem would return.

I've had masters fail and leak, but never get better after a cool down .... Maybe others have a different experience, though....
 
This reminds me of a brake problem I once had. Pedal would sink to floor on light brake application at very low speed or when my foot was resting lightly on the pedal to maintain position at a traffic light. But under normal driving, or firm pedal pressure, the pedal would remain high. Weirdest thing. My theory was worn seals were permitting brake fluid to bypass the piston under the low pedal pressure, but higher pedal pressure was forcing the seals against the cylinder and better sealing the piston. Don't know if this idea/opinion was correct but a new master cylinder fixed the problem.
 
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