SeditiousCanary
New Member
Hey all, first time poster here.
Preface:
I have a 97 Disco with a strange brake issue. It started as a failed master cylinder (MC). Pedal went to the floor. No brakes. Happened in my driveway. I've had this issue in other cars, and figured I just needed a new master cylinder.
The TL;DR is at the bottom.
Chapter 1 - New Master Cylinder, New Problem
I ordered, then installed the 1st new MC (foreshadowing...), and brakes worked great in the driveway. I took it out for a test drive. About a mile into the drive, I realized the brakes were slowly being applied even when I took my foot off the pedal, and the pedal was getting harder and harder. When I pulled over to inspect it, all the wheels were locked, and the brake pedal was so hard it couldn't be pressed. I couldn't even move the Disco because the brakes were stronger than the engine. I cracked the brake line open at the 1st new MC, and bled off pressure from the system. I was able to make it home.
Chapter 2 - What the Hell is Going On In There?
Its a 27 year old car I have had for five years, and I drove it from Seattle to Washington, DC this summer to relocate. I've had no issues with it until now, but the flex brake line looked to be original, or at the very best "not really very new". I figured maybe the flex brake line was failing on the inside, so I got all new flex brake line, installed them, bled the system, but the issue remained exactly the same. Drive about a mile, and the brakes slowly come on, and I had to stop to release pressure to get home again.
Chapter 3 - Did I Do It Right?
At this point, I figured maybe I didn't install the 1st new MC correctly, or there was an adjustment that I missed, so I pulled the 1st new MC, confirmed all the relevant dimensions for plunger depths and the like were the same as the OEM MC, did a bench bleed on the 1st new MC, reinstalled it, then did a full system flush and bleed with new DOT4 fluid. I took it for a test drive, and the same thing happened.
Chapter 4 - What the Hell is Going On In There? Part II
Having done all the seemingly obvious things, I turned to my Google Fu, and looked up what other people were talking about. There were no solid answers that sparked eureka moments, but I did pull the error codes to see if the ABS was reporting anything out of the ordinary. There was one code about an EVAC issue, but nothing about brakes. Google results asl suggested the ABS may be a cause, and to try removing the 40A fuse for the ABS pump, which several people had pretty close sounding issues to mine had reported worked to fix their problem. I pulled the fuse, but the issue reoccurred.
Chapter 5 - I've Had Bad Luck, But This Is Ridiculous
By now, I've come to the conclusion the 1st new MC is defective, because its not letting fluid back in to itself. I get a 2nd new MC, bench bleed it, install it, bleed it, and it still does the same thing.
Chapter 6 - Acceptance, or Loss of Hope, I Cannot Tell Which
Im at a total loss here. I cannot think of anything that would cause this, so I'm turning to you all in hopes that you can think of something I've missed, or ask the right question that I have not. Thanks!
TL;DR Version:
Things I've Done to "Fix It" that "Have Not Fixed It":
1. I figured the flex brake like was likely bad, so I replaced all the flex brake line, bled the system, but the brakes and brake pedal did the same thing.
2. I pulled the 1st new MC, did a bench bleed, then reinstalled it, fully replaced the DOT4 in the system, but the brakes and brake pedal did the same thing.
3. I pulled the error codes, but the only one I saw was for an EVAP issue that was unrelated.
4. I removed the 40A ABS fuse, and tested again, but the brakes and brake pedal did the same thing.
5. I ordered another MC thinking maybe I got a bad one. I removed the 1st new MC, bench bled the 2nd MC, installed it, but the brakes and brake pedal did the same thing.
Preface:
I have a 97 Disco with a strange brake issue. It started as a failed master cylinder (MC). Pedal went to the floor. No brakes. Happened in my driveway. I've had this issue in other cars, and figured I just needed a new master cylinder.
The TL;DR is at the bottom.
Chapter 1 - New Master Cylinder, New Problem
I ordered, then installed the 1st new MC (foreshadowing...), and brakes worked great in the driveway. I took it out for a test drive. About a mile into the drive, I realized the brakes were slowly being applied even when I took my foot off the pedal, and the pedal was getting harder and harder. When I pulled over to inspect it, all the wheels were locked, and the brake pedal was so hard it couldn't be pressed. I couldn't even move the Disco because the brakes were stronger than the engine. I cracked the brake line open at the 1st new MC, and bled off pressure from the system. I was able to make it home.
Chapter 2 - What the Hell is Going On In There?
Its a 27 year old car I have had for five years, and I drove it from Seattle to Washington, DC this summer to relocate. I've had no issues with it until now, but the flex brake line looked to be original, or at the very best "not really very new". I figured maybe the flex brake line was failing on the inside, so I got all new flex brake line, installed them, bled the system, but the issue remained exactly the same. Drive about a mile, and the brakes slowly come on, and I had to stop to release pressure to get home again.
Chapter 3 - Did I Do It Right?
At this point, I figured maybe I didn't install the 1st new MC correctly, or there was an adjustment that I missed, so I pulled the 1st new MC, confirmed all the relevant dimensions for plunger depths and the like were the same as the OEM MC, did a bench bleed on the 1st new MC, reinstalled it, then did a full system flush and bleed with new DOT4 fluid. I took it for a test drive, and the same thing happened.
Chapter 4 - What the Hell is Going On In There? Part II
Having done all the seemingly obvious things, I turned to my Google Fu, and looked up what other people were talking about. There were no solid answers that sparked eureka moments, but I did pull the error codes to see if the ABS was reporting anything out of the ordinary. There was one code about an EVAC issue, but nothing about brakes. Google results asl suggested the ABS may be a cause, and to try removing the 40A fuse for the ABS pump, which several people had pretty close sounding issues to mine had reported worked to fix their problem. I pulled the fuse, but the issue reoccurred.
Chapter 5 - I've Had Bad Luck, But This Is Ridiculous
By now, I've come to the conclusion the 1st new MC is defective, because its not letting fluid back in to itself. I get a 2nd new MC, bench bleed it, install it, bleed it, and it still does the same thing.
Chapter 6 - Acceptance, or Loss of Hope, I Cannot Tell Which
Im at a total loss here. I cannot think of anything that would cause this, so I'm turning to you all in hopes that you can think of something I've missed, or ask the right question that I have not. Thanks!
TL;DR Version:
Things I've Done to "Fix It" that "Have Not Fixed It":
1. I figured the flex brake like was likely bad, so I replaced all the flex brake line, bled the system, but the brakes and brake pedal did the same thing.
2. I pulled the 1st new MC, did a bench bleed, then reinstalled it, fully replaced the DOT4 in the system, but the brakes and brake pedal did the same thing.
3. I pulled the error codes, but the only one I saw was for an EVAP issue that was unrelated.
4. I removed the 40A ABS fuse, and tested again, but the brakes and brake pedal did the same thing.
5. I ordered another MC thinking maybe I got a bad one. I removed the 1st new MC, bench bled the 2nd MC, installed it, but the brakes and brake pedal did the same thing.
