Power brake question

[blown motor]

Asking for a friend with a 62 Jag E-type. He just restored this car and has a crazy brake issue. The car has two master cylinders, one for the front and one for the back. After a 15 mile drive last night the front brakes came on by themselves! He did not touch the pedal, the car just started slowing down because the brakes had come on. He cracked the front line at the MC to relieve the pressure and it was fine. He drove it home without issue. This is not the first time it has happened. We're stumped.   

[1 Wild R/T]

Each master has it's own pushrod & there's a balance bar between them that connects to the pedal link... The pushrod for the front master is probably adjusted a touch long...... If the piston in the master cylinder doesn't return fully home the fluid gets trapped between the M/C piston & the caliper pistons & as it heats up iy expands slightly which causes the brakes to self apply.....

Haven't worked on an E type in a long time so without research I'm just covering it based on general operation knowledge... But I'm sure there's an adjustment..

[RUNCHARGER]

Wow: This is why I have never owned an english bike or car.

[Chryco Psycho]

  Wilds diagnosis makes sense to me

[blown motor]

Each master has it's own pushrod & there's a balance bar between them that connects to the pedal link... The pushrod for the front master is probably adjusted a touch long...... If the piston in the master cylinder doesn't return fully home the fluid gets trapped between the M/C piston & the caliper pistons & as it heats up iy expands slightly which causes the brakes to self apply.....

Haven't worked on an E type in a long time so without research I'm just covering it based on general operation knowledge... But I'm sure there's an adjustment..

Thanks Wild!    I'll pass it along.

[1 Wild R/T]

The reality is twin masters is still a very trick way to set up brakes..  Still used on serious race cars....Completely isolated systems, the bias adjustment instead of trying to limit pressure just changes the leverage/ratio between the pedal & the two masters....   

[jimynick]

Wow: This is why I have never owned an english bike or car.

The E-type Jag has been called, by some, the most beautiful production car built. Where it fell down, was in not having the electrical system built by A/C Delco and in forgetting that here in "the colonies" we get snow and ice that needs salt to tame it and the combination can be fatal to enjoying that British car. You can actually buy a T-shirt emblazoned with "Lucas, prince of darkness" LOL 

[1 Wild R/T]

Wow: This is why I have never owned an english bike or car.

The E-type Jag has been called, by some, the most beautiful production car built. Where it fell down, was in not having the electrical system built by A/C Delco and in forgetting that here in "the colonies" we get snow and ice that needs salt to tame it and the combination can be fatal to enjoying that British car. You can actually buy a T-shirt emblazoned with "Lucas, prince of darkness" LOL 

Why do the Brits drink warm beer?   Cause Lucas made their refrigerators...

[Chryco Psycho]

 
Why would you name your electrical system Lucas [God of Darkness] & expect the lights or anything else to work LOL

[BIGSHCLUNK]

You cant say Lucas and electronics in the same sentence............ 

[1 Wild R/T]

Tried to post this a few days ago but the site as having "issues"..

[Skid Row]

 I learned my lesson on British Leyland/ Lucas cars with a 1959 Hillman Husky.

[RUNCHARGER]

When I bought my first set of decent valve springs for a big block, my friend Bob at the engine shop told me they were the front coils off a Hillman Minx.