no breaks!! help

[rambam!!]

im going to buy a 98 cummins but the real brake lines are shot and i was wondering if there is a way to stop the leaking from the rear end so that the front breaks worked so i could drive it home with me that day any sugestions?

 

[iSlacker816]

The front brakes should work still but the pedal will be spongy

 

[NYCruiser]

X2 - Front and rear brakes should be on separate circuits and reservoirs from the master cylinder.
You could pull the rear lines from the master cylinder, fill the cylinder, and cap the holes.
My recommendation, however, is have it flat bedded.

 

[chopperman1]

The front brakes won't work IMHO. After the first couple pedal pushes all the fluid will be gone. The braking system is reliant upon being a sealed system, the proportioning valve typically supplies X percent to the front and X percent to the back, but again with a sealed system. Without a sealed system all of the pressure is going to take the path of least resistance, in this case the broken/leaking brake lines. Only way I see this happening is removing the rear lines at the proportioning valve and plugging the valve. If it were me... I would be flat bedding or towing it as that's the safest way.

 

[RamV10]

The front brakes won't work IMHO. After the first couple pedal pushes all the fluid will be gone. The braking system is reliant upon being a sealed system, the proportioning valve typically supplies X percent to the front and X percent to the back, but again with a sealed system. Without a sealed system all of the pressure is going to take the path of least resistance, in this case the broken/leaking brake lines. Only way I see this happening is removing the rear lines at the proportioning valve and plugging the valve. If it were me... I would be flat bedding or towing it as that's the safest way.

You have it backwards. When you push on the brakes the lack of resistance with force the proportioning valve to close the rear fluid from passing. That was why the system has the valve. So if you blow a line or wheel cylinder you still have brakes. That is why you have a divided master cylinder Two separate systems when a leak happens on either front or rear.

 

[chopperman1]

You have it backwards. When you push on the brakes the lack of resistance with force the proportioning valve to close the rear fluid from passing. That was why the system has the valve. So if you blow a line or wheel cylinder you still have brakes. That is why you have a divided master cylinder Two separate systems when a leak happens on either front or rear.

Great to learn something new! I've never seen a valve that had the ability to "shut off" a specific line. The ones I've dealt with are basically a piston operated system, applies specific pressure/balance based on it's design. My experience is also with "classic" cars with a separate valve and not built in to the MS which could be the difference.

 

[RamV10]

A proportioning valve is a neutral valve when pressures are equal. The piston remains in the middle in a neutral position. When one side or the other looses pressure it forces the valve to block the loss of pressure side.
Sometimes once the proportional is pushed to one side or the other it is hard to get it reset to the neutral position. Most of the time takes a bleeder to get it back.
This was installed as a safety devise to prevent complete brake failure.