A dual line system is a safety item. If a brake line/brake hose lets go you will still have brakes on one axle, you may not stop on a dime but it will stop you. A single line system will leave you with out any brakes at all if one brake line/hose lets go. American made cars have had a dual line systems since 1968.
If fluid is lost due to component failure, you will get total brake failure (loss of all braking except parking/emergency brake) on a single circuit system. A dual circuit system will only fail in one circuit, leaving the remaining circuit working. It is therefore safer.
hydraulic brake booster (power brakes)
replace brake line the damage to the line or if the jb weld gets into the line it will affect how the system works.
Brake system bleeding is working on hydraulic brake systems. This is when the brake line has air bubbles in the line. You open the bleed screw on the caliper and pump fluid through the lines until all of th bubbles are gone from the system, an air bubble will steal pressure from the brake system and prevent good operation.
If you have not opened the brake system ie. taken off any lines or lost any fluid, you should not have to bleed a brake system. Brake jobs are best done by experienced technicians.
Vapor lock in a brake or fuel system is pretty much a thing of the past. If you are experiencing it, then check to see if a brake line is routed too close to the engine, exhaust manifold, or any of the exhaust system. Also drain the brake system and install fresh brake fluid. It may be contaminated with moisture.
The year, make, model and what you have done to the brake system so far would help.
I need to see the brake diagram for a 95' cadillac sedan deville
Yes, there a diagram that illustrates the brake system in a Chevy Impala. It is found in the maintenance manual for the car.
There is a brake line vent tube on most Volvo trucks which allows excessive pressure to be released. This prevents catastrophic failure to the system.
When a high pressure brake line or power steering line is disconnected near the pistons or any where besides reservoir. air may get into the system. the only way to get the air out of the system is by bleeding system, or purging system. if not done the result will be spongy brake's squealing and whining sounds when turning.