Lost Brakes while driving (1 Viewer)

[jtallequipment]

I have an 83 US FJ40. I purchased after it underwent 10 year restoration, that was abandoned 75% complete. The vehicle would start and ran but was not driven for approx 12 years. The work that was done seems to be a very high level. The prior owner is not accessible, so I do not have a lot of history on the vehicle.

I've spent the last year fixing and finishing the obvious and have driven locally about 300 miles with no brake issues. Yesterday I visited a friend (approximately 10 miles away from my house) and we reset timing, as I was getting some detonation. Truck was running great, but on the way home, some highway, probably first time in 12 years its seen 55, I hit the brakes at an intersection and the pedal went straight to the floor. Initially it gave some brake effect, but then nothing . My foot was right on floor board. Used emergency brake and pulled over. Pumped brakes and they came back up, so when traffic lightened up, I got back on the road and got home. Pretty scary sh*t.
Checked for leaks - None at master cyclinder, or any brake lines. Repumped brake and after 2 or 3 pumps came back up and holds with engine off. Will slowly bleed down with engine running, but not to the floor.
When I release emergency brake, dash brake light dims, but stays on (had same issue prior to yesterday event- I did add some DOT 3 when I first got the truck. as it was at min -thought that would shut off light when it didn't I assumed it was a ground issue). I do not know if PO used synthetic fluid and if so, could mixing even a small amount cause a problem like this. I assume not and that it's probably internal in Master cylinder, not the brake booster, as it didn't become hard to brake but actually would not brake at all.


Has anyone experienced something like this before?

Thanks Jim

 

[whitey45]

Internal master leak, have had a few landcruisers do this!

 

[jtallequipment]

Internal master leak, have had a few landcruisers do this!

Thank You Whitey. I'm thinking the same. Not a lot of fun to experience.
Jim

 

[Howard705]

Most Likely MC as stated above. Not just LCs - any vehicle.

 

[45Dougal]

"When I release emergency brake, dash brake light dims, but stays on (had same issue prior to yesterday event"

When the brake warning light comes on when you brake, that's because you have a brake fault! Something you should resolve before driving!

You can try and remove each of the wires in turn from the master cylinder, and see if the light still comes on - that tells you which circuit has lost pressure.

Probably master leak as stated, but worth checking the adjustment on the problem circuit too.

 

[3_puppies]

probably a good idea to flush all the old fluid out when bleeding with the new master

 

[1MOA]

Master cylinder in the brakes is toast.
More specifically the seal on the piston is torn from over extension and is gone.
I will let you in on a break system secret. Never push a brake pedal to the floor while the brake system is being rebuilt when you do you push the piston and it's seal out of the cylinder and when you do it rip's the seal as it pulls the piston back into the cylinder. Put a block of wood or a brick under a brake pedal if you are going to leave it for any length of time so it is not inadvertently pushed down. It's one of the most common things broken when cars go into the shop for restorations. It always gets blamed on the car sitting but it's because someone out of habit got in it and pushed the brake pedal down.

 

[jtallequipment]

"When I release emergency brake, dash brake light dims, but stays on (had same issue prior to yesterday event"

When the brake warning light comes on when you brake, that's because you have a brake fault! Something you should resolve before driving!

You can try and remove each of the wires in turn from the master cylinder, and see if the light still comes on - that tells you which circuit has lost pressure.

Probably master leak as stated, but worth checking the adjustment on the problem circuit too.

"When the brake warning light comes on when you brake"
Actually stays on but dimmer when emergency brake disengaged. Good advice to check wires.
The thing that gets me is I had no brake from pedal. Shouldn't I have had one circuit still working?

Thanks
Jim

 

[jtallequipment]

Master cylinder in the brakes is toast.
More specifically the seal on the piston is torn from over extension and is gone.
I will let you in on a break system secret. Never push a brake pedal to the floor while the brake system is being rebuilt when you do you push the piston and it's seal out of the cylinder and when you do it rip's the seal as it pulls the piston back into the cylinder. Put a block of wood or a brick under a brake pedal if you are going to leave it for any length of time so it is not inadvertently pushed down. It's one of the most common things broken when cars go into the shop for restorations. It always gets blamed on the car sitting but it's because someone out of habit got in it and pushed the brake pedal down.

Good advice, that someone was probably me who pressed the pedal.
I have put about 300 miles on it since back on the road (20 miles at a time) with no indication of problem. Pedal was high and tight not soft and then out of nowhere BOOM.
The thing that gets me is I had no brake from pedal at all. Shouldn't I have had one circuit still working? or is the 2 circuit system only to protect against brake line failure front or back.

 

[pb4ugo]

Yes, with complete failure, its another indication it's the master. Personally I'd inspect frt and rear brakes too. Dual master systems are designed so you'll still have brakes if either the ftt or rear fail. It's also why emergency brakes operate with a totally independent system than the main braking system . That's why using line locks as emergency brakes are a bad idea and a professional shop that installs them as such can be held liable.

 

[3_puppies]

just a WAG here
maybe only the fronts were working, the rears weren't
now you have another issue with the master and now both are not working, hence no brakes at all.
having a rig sit for 12 years and not going thru something as critical as brakes, was not a great idea.
especially as standard brake fluid atracts water and then corrosion follows

 

[jtallequipment]

just a WAG here
maybe only the fronts were working, the rears weren't
now you have another issue with the master and now both are not working, hence no brakes at all.
having a rig sit for 12 years and not going thru something as critical as brakes, was not a great idea.
especially as standard brake fluid atracts water and then corrosion follows

That could be, but pedal feel and stopping distances were good before this happened.
Visible inspection of brakes and lines were done and about 300 miles of soft test driving. No leaks visible, all components appear new and are probably much newer then 12 years, as this was a 12 year project that I assume came together about 5 years ago (age of the tires).

New fluid will be part of the repair. Thanks Jim

 

[45Dougal]

just a WAG here
maybe only the fronts were working, the rears weren't
now you have another issue with the master and now both are not working, hence no brakes at all.
having a rig sit for 12 years and not going thru something as critical as brakes, was not a great idea.
especially as standard brake fluid atracts water and then corrosion follows

Totally agree - front brakes only would give a good pedal feel (albeit with the red warning light).
Putting pressure like that on the middle seal will eventually cause the catastrophic failure seen.
The back circuit is probably pumping up because they're badly adjusted.

 

[pb4ugo]

The rear brakes give pedal height, as the rears wear the pedal height goes down. Adjusting the rears will raise the pedal height. If the rear brakes fail the pedal will drop significantly but will not go to the floor if the frt brakes still create pressure. I agree the seals between the cylinders probably failed.