scout80lover
New member
Good afternoon y'all. I've run into a bit of a head-scratcher and am seeking any advice since I seem to be missing something obvious.
Been doing brakes and mechanical work for over 30 years, but I'm stumped at the moment.
1) vehicle model.
Scout 80
2) production date/or year model.
1965
3) two wheel drive or four wheel drive.
4x4
4) type of transmission (and transfer case if applicable).
T90
5) if 4x4, which axles front and rear.
Not sure offhand
6) which engine variation.
152
7) which ignition system variation.
stock with a pertronix conversion in the distributor
8) which fuel system variation.
factory dual tank
9) which brake system variation.
factory-style single reservoir master cylinder
stock rear drums, factory original ebrake & components, front disc conversion (https://scoutparts.com/Disc_Brake_C...e_4x4_Scout_80_800__Scout_80_Scout_800/p18307)
10) non-oem modifications present which May impact a response.
When I purchased the Scout about 4 years ago, I replaced the master cylinder, just out of good measure as it had been sitting for years. About a year into driving her around, I did the front disc brake conversion. Everything has been working great since. Daily driver.
Just recently, the brakes have started getting stuck in the applied position, like somebody was standing on the pedal after using them a couple times. Initially thought it was just affecting the rears. Inspected the ebrake cabling...but everything actuates great, no binding or sticking. Figured, what the hell, maybe the rear cylinders had finally given up after all these years and were sticking. Replaced them with new rear cylinders. These are non-self-adjusting rears, so require manual adjustment, which I've done on a ton of vehicles. Bled everything, condition is still happening, brakes get stuck on. All the hardware in the drums appears fine, no damage visible to anything.
Palm to forehead, realized maybe it is master cylinder as I discovered the front are getting stuck applied as well. Swapped the master cylinder for a new one. Bench bled it and it got stiffer and stiffer as the air came out as one would expect. Just got everything installed and bled and they are STILL remaining stuck after depressing the pedal a couple times.
All the hard-lines are factory original and completely undamaged...no kinks, bends, nada. The front flex lines are only like 3 years old and undamaged as far as I can tell. Even the single rear flex hose at the differential looks fine on inspection, no cracking or binding. The portioning block is original and looks fine, no visible damage. On visual inspection, everything might as well be right out of the factory.
For the life of me I cannot figure out what on earth is keeping pressure in the lines and seizing all 4 wheels rock solid. Brand new master cylinder. The only time I have ever had this happen in the past was when rebuilding a 1950 Chevy master cylinder and having missed cleaning the pressure relief port in the cylinder due to old residue that I didn't notice. This master cylinder is squeaky clean and clear as it just arrived new in the mail yesterday.
Can anyone think of any gotcha tricks that I'm missing? Captain Obvious is certainly scratching his head at the moment.
Been doing brakes and mechanical work for over 30 years, but I'm stumped at the moment.
1) vehicle model.
Scout 80
2) production date/or year model.
1965
3) two wheel drive or four wheel drive.
4x4
4) type of transmission (and transfer case if applicable).
T90
5) if 4x4, which axles front and rear.
Not sure offhand
6) which engine variation.
152
7) which ignition system variation.
stock with a pertronix conversion in the distributor
8) which fuel system variation.
factory dual tank
9) which brake system variation.
factory-style single reservoir master cylinder
stock rear drums, factory original ebrake & components, front disc conversion (https://scoutparts.com/Disc_Brake_C...e_4x4_Scout_80_800__Scout_80_Scout_800/p18307)
10) non-oem modifications present which May impact a response.
When I purchased the Scout about 4 years ago, I replaced the master cylinder, just out of good measure as it had been sitting for years. About a year into driving her around, I did the front disc brake conversion. Everything has been working great since. Daily driver.
Just recently, the brakes have started getting stuck in the applied position, like somebody was standing on the pedal after using them a couple times. Initially thought it was just affecting the rears. Inspected the ebrake cabling...but everything actuates great, no binding or sticking. Figured, what the hell, maybe the rear cylinders had finally given up after all these years and were sticking. Replaced them with new rear cylinders. These are non-self-adjusting rears, so require manual adjustment, which I've done on a ton of vehicles. Bled everything, condition is still happening, brakes get stuck on. All the hardware in the drums appears fine, no damage visible to anything.
Palm to forehead, realized maybe it is master cylinder as I discovered the front are getting stuck applied as well. Swapped the master cylinder for a new one. Bench bled it and it got stiffer and stiffer as the air came out as one would expect. Just got everything installed and bled and they are STILL remaining stuck after depressing the pedal a couple times.
All the hard-lines are factory original and completely undamaged...no kinks, bends, nada. The front flex lines are only like 3 years old and undamaged as far as I can tell. Even the single rear flex hose at the differential looks fine on inspection, no cracking or binding. The portioning block is original and looks fine, no visible damage. On visual inspection, everything might as well be right out of the factory.
For the life of me I cannot figure out what on earth is keeping pressure in the lines and seizing all 4 wheels rock solid. Brand new master cylinder. The only time I have ever had this happen in the past was when rebuilding a 1950 Chevy master cylinder and having missed cleaning the pressure relief port in the cylinder due to old residue that I didn't notice. This master cylinder is squeaky clean and clear as it just arrived new in the mail yesterday.
Can anyone think of any gotcha tricks that I'm missing? Captain Obvious is certainly scratching his head at the moment.
