Impossible brake problem
Thread Starter
Heel & Toe
Joined: May 2022
Posts: 19
Likes: 5
From: Bradenton, Fl
Impossible brake problem
The brakes on my c4 went out completely while driving and the pedal would just go to the floor and no amount of pumping would bring them back. I had to use downshifting and the parking to gently drive it all the back home. That was four months ago then yesterday I showed my mechanic the problem and to my great surprise the brakes were back to working perfectly. Can any of my fellow Corvette lovers tell me what they think the problem is? Nat
Drifting
Joined: Feb 2016
Posts: 1,384
Likes: 339
From: Simi Valley CA
If it went to the floor that's most likely the MC. It is possible the seal wouldn't hold pressure maybe due to the heat and then is working again now that it is cold. Do you have brake fluid leaking down the firewall under the MC/PB? I would also flush all the old brake fluid out of the system. It goes bad after several years and most older cars have 10+ year old brake fluid in them.
If it was the PB the brake pedal would be very stiff, but brakes would work. If it was an individual caliper the brakes would still work on either the front or the back. I disconnected the rear brake lines on a roller and the fronts still worked.
If it was the PB the brake pedal would be very stiff, but brakes would work. If it was an individual caliper the brakes would still work on either the front or the back. I disconnected the rear brake lines on a roller and the fronts still worked.
Thread Starter
Heel & Toe
Joined: May 2022
Posts: 19
Likes: 5
From: Bradenton, Fl
Thank you for the reply! My mechanic My mechanic suggested a couple of things. He said its not the MC but probably just need to flush the brake fluid and put in new. I'm thinking something like synthetic DOT 4? And also suggested it could be the brake check light sensor that plugs into the MC or the pressure sensor that also plugs into the MC. I am not really sure about that but there are two sensors that plug into the MC. Does this make any sense to you? I am not a great mechanic my self but can do most of the very basic stuff. Also the car idles at about 1200 rpm and he thinks it is the idle sensor causing that. Any thoughts about that? THANKS!!!
Drifting
Joined: Jan 2005
Posts: 1,354
Likes: 325
From: San Antonio Tx
I agree with your mechanic. It could be water in the brake fluid boiling. When it cools down the brakes are normal again. I had that fun experience once. Now I flush my brake system regularly. The sensors do nothing but turn on the brake warning light.
Drifting
Joined: Feb 2016
Posts: 1,384
Likes: 339
From: Simi Valley CA
It would have to be a lot of water in the system for the brake pedal to go to the floor and you have no brakes. I don't think you would have anywhere near decent brakes when cold if that was the case. None of the sensors failing would cause the pedal to go to the floor. Unless they're leaking. Check for leaks on your tires too. A leaking caliper will leave a trail down the tire. Especially if it has sat for 4 months.
Drifting
Joined: Feb 2016
Posts: 1,384
Likes: 339
From: Simi Valley CA
Be sure to post what your outcome is. Helps others out. I also flushed the old brake fluid out of the 92 I recently bought. It is a manual trans car. I noticed when stopping after it was warmed up that the brakes were grabbing. In nuetral rolling at less than 1 mph without the brake pedal applied it would stop like the brake was applied. It was very subtle, but I could feel it. After flushing the system (and changing the non working PB and leaky MC separately) twice using Prestone Dot 4 synthetic brake fluid it doesn't do that. The brake lines on this run straight down the MC right next to the cat. I feel the dot 4's higher boiling temp helps.
Thread Starter
Heel & Toe
Joined: May 2022
Posts: 19
Likes: 5
From: Bradenton, Fl
When on the day the brakes went out I had only driven about a mile down the road when it happened. When I got in the car and pulled out of the parking lot they were working fine. then a mile or two later Wam! pedal just hit the floor. When I finally eased it back home I parked it and let it sit until I felt like messing with it. I only drive it about once a month and might put 1000k miles a year. Probably more like 200 miles a year. Thats why it has such low miles on it. I don't see any fluid leaking on the tires or any leaks at all. The car is a super nice original 1994 and in the last 25 years never had a problem with it. It still has the original tires on it, original plugs and wires, it is pretty much just like the day I bought it.
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Melting Slicks
Joined: May 2014
Posts: 2,895
Likes: 592
From: New Port Richey FL
I personally go with the Master Stroking thru, by chance did you hear the ABS pump running I had bad sensor once that ran my pump on dry pavement and the car wouldn't slow and pedal was low
Melting Slicks
Joined: May 2014
Posts: 2,895
Likes: 592
From: New Port Richey FL
. Then all of a sudden the bit falls out brakes are good again until the next time it get in again
Thread Starter
Heel & Toe
Joined: May 2022
Posts: 19
Likes: 5
From: Bradenton, Fl
New tires? Heck, they are only 28 years old.I have to say they are a bit hard and cracked but still have full tread. But you are right, I have plans for new rubber and to sent out my Fiske rims for polishing and new clear coat before I throw on new tires. Do you have a recommendation which tire I should go with?. It came with Goodyear Eagles but have not been able to find that exact same tire again.
Melting Slicks
Joined: Feb 2015
Posts: 2,069
Likes: 262
From: Park Ridge New Jersey
New tires? Heck, they are only 28 years old.I have to say they are a bit hard and cracked but still have full tread. But you are right, I have plans for new rubber and to sent out my Fiske rims for polishing and new clear coat before I throw on new tires. Do you have a recommendation which tire I should go with?. It came with Goodyear Eagles but have not been able to find that exact same tire again.
