Ok I have a 07 ram 2500. I keep busting the break line on the master cylinder the one closest to the fire wall. it has a hydroboost system on it I really dont know anything about it. And the fluid is so hot it set any plastic on fire. Thanks in advance for any help.

 

When you say that you bust the brake line, do you mean the hard line cracks, or, does the fitting come out of either the junction box or master cylinder?
If the fitting is coming out then check the threads. It may have been over-torqued and stripped the threads. Torque on the fitting is only 14 ft/lbs.

 

It splitting the steel break line.

 

Maybe we can determine which brake the line goes to.
Are you able to tell if all of your calipers working properly?

 

its the line that goes from the master cylinder to the abs. There are two of them. The one that is busting is the first from the fire wall. I checked the calipers there fine.

 

There are a couple of different brake setups for your model. From your description, the two lines supply pressure either; diagonally (one rear and one front wheel per line), or, one line for front brakes, one for rear. I think troubleshooting steps would be same regardless, but it is something I would recommend you research to understand what is being supplied by the broken line.
This is an unusual situation, and I doubt many on this forum have experience with hard brake lines bursting under pressure. At least I'm assuming that the split line is being caused by pressure.
I recommend that you start by bleeding the brakes at each caliper. First gravity bleed to check that fluid is flowing, then force flow by pumping the brake pedal or using a brake bleeder tool. Goal of this step is to see that fluid is flowing to each caliper. I suspect there is blockage at one or two calipers. Make sure you are comfortable with brake bleeding so you don't introduce air into the system.
I hope you did not get air in your brake junctions or ABS when the line split. That'll be next project once you figure out cause of split line.
Where are you getting your replacement brake lines? Making them yourself? Could line quality be the problem?

 

The only time I have seen brake lines burst, is when they were rusted beyond usefulness. If you are blowing up new lines, think I would try a different source for lines first...... It takes a LOT of pressure to blow them up..... Even STANDING hard on the brake pedal shouldn't phase them.

 

Heyyou, I was thinking the same thing. It seems like the steel line would be the strongest point in the system and that fluid would blow past the seals in the master cylinder before the line would break. I never heard of a new hard line breaking. We will all be smarter when we figure out what the problem is here.
OP mentions fluid was hot, so I'm thinking there is some high pressure being made somewhere.

 

Is this a steel or plastic line?

Steel lines are rated for approx. 3000psi and that's usually with a 3-1 safety factor.

If the flares are not done correctly I suppose that could lead to a crack but busting NEW hard lines without some kind of pre-existing defect or user installed error is near impossible.

And even saying a user installed error could lead to a failure, steel lines are pretty forgiving.
The double flare (done correctly) will usually seal up even with a little misalignment.

Getting back to the hydroboost.
You get brake assist from a pressure line from the power steering pump.
In the 2500+3500 series trucks, that pressure is approx. 1800 psi. Still not enough to burst a NEW hard line.

As far as how hot the fluid is. The act of compressing the fluid will increase it's temp., but it shouldn't get so hot that it melts plastic!

I'm not familiar with the layout of the lines on a 2500 + 3500 series truck but maybe a exhaust leak could explain the melted plastic?
If the lines are plastic, and you have some source of heat heating up the plastic lines, that could definitely compromise those plastic lines leading to a failure.