Hy HFfarms, I am a mechanic, not an engineer and I don't profess to be one. The fact that I have never seen this brake line plumbing system until you showed us your trucks system sets a red flag in my head. Over the years there have been many different things tried in the field of vehicles, some ideas were good and have continued and been refined and improved. The fact that this particular system was/is not in widespread use tells me it was not something that added a benefit to to the more common single application to the brake booster system. As I said previously, if it were my truck I would remove the second output line from the booster back to the master cylinder, plug that port on the booster and run the system with one output from the master cylinder and one output from the brake booster to the braking piping system. As that is the system we are more used to seeing in a single braking system I think it will work fine. It is your truck and you may restore/rebuild it as you see fit, please verify that whatever system you decide on is safe before you venture out onto the road.
I completely agree to a point. The fact that it is factory makes me breathe easy, and the stopping power of the bigger hydro-vac I see as nothing but a good thing. It could be that as a factory upgrade, it came with a price tag that most buyers didn't care for, and thus it is not as common because of it. Much like the quadrasteer silverado's of the early 2000's as an example. Not common, most look at it cross eyed, but it is arguable more bullet-proof than the standard 8.5" ring gear straight axle and allows significant increase in capability. Most just didn't want the $2k price jump for it to be installed, and opted for the standard route instead. Maybe these brakes are of a similar situation. Money is a great motivator.
As an engineer, I can appreciate the system, but I don't fully understand the need for the return. My only though it that it somehow uses a progressive capability that requires more fluid when heavily loaded with more brake pressure, and thus bypasses a variable amount back to the master at lesser loads (less pedal travel). BUT, i do not understand the exact physics of this unit so this is only a hypothesis.
Regardless of it all, I have a new 3 line hydrovac in my shop, and the master is being disassembled and cleaned for inspection and reuse. Should everything check out, its going back in. Should it not, then due to lack of parts, we are going the single line route with the spare unit I have here. Either way, brakes will be 100% before this truck moves again, I can promise anyone that. Ive lost 3 vehicle in my life to brake failures, so I don't mess around with it. Aint no kill like overkill when it comes to brakes.
