Boosters or Master cylinder?

[FSJNut]

Started the 320 up after it had been sitting for a couple of months, and started right up. That's the good part. \nPut my foot on the brake to go through the gears and my foot went to the floor. \nPlenty of fluid in both reservoirs. No leaks at the wheels. I can hear an air sound around the location of the boosters when I put my foot on the brake with the engine running. So, what do you think? Boosters or MC?

[rcb]

I'm betting the booster if you can hear whooshing.

[Acesneights]

With someone helping you start at the back wheels and crack the bleeders. See if there is any fluid pressure at the wheels. Then go to the boosters then the master. The hydrovacs are notorious for internal leaks when they sit.\nFor years my familys 220 would lose the pedal if it sat more than a month or so. We would refill and bleed and it would not lose a drop as long as we were using it. Never quite got that. You would think if there is a leak, it woild still be there.\nI never liked the remote boosters on these. Always troublesome. My 72 has a vac booser up front like a pickup with the mater bolted to it. It sat for an estimated 20 yrs and still had a pedal when I rescued it.\nTry bleeding it first and go from there. If you have a serious leak, it will show itself.

[rcb]

On that subject, other than linkage, is there any other concern if you swap in a different booster?

[Acesneights]

Well the concern is always when playing around with different non oem parts is what effect will it have. Not sayin OEM is best. In many cases OEM is not the best but when it comes to modifying a brake system on some that weighs 10,000-14,000 lbs I would imagine the main concern would be liablity if it were involved in a fatal accident.

[rcb]

I was meaning more in the line of special features the dual booster may provide as compared to the typical truck setup. If its good enough for a 1 ton with a 19k gcvwr, capacity wouldn't phase me too.much. \n\nThe setup is just a little cumbersome. And speaking of brake failures, what is the deal with the brakes on rv's? I've been looking at many and they all seem to have brake issues (or had). We deal a lot with farm and truck equipment, some of it far older than these... but I haven't seen so many "in need of brake work" disclaimers. It's one of the reasons I've started considering a complete drive line swap should I find a 210. \n\nWe have many vehicles from the 60s and early 70s that rarely have any brake issues. Is it just the lack of use or possibly neglect old motorhomes usually see?

[FSJNut]

The boosters look original - old and rusty. I'm thinking it would be a good idea to replace them. I was thinking if the boosters quit you would still have good pedal, just no power assist. Like a conventional MC/booster setup would do. I guess these are essentially remote master cylinders as well.\nAnother piece of info - as soon as I turn off the engine I hear a loud 2 second long air rush. And then when I press the pedal with the engine not running it doesn't seem to have any residual vacuum.

[rcb]

Make sure to check your vacuum lines and any vacuum reservoirs.\n\nAnd by check, I mean flex the lines. I've seen nearly invisible cracks. Same thing for reservoirs.

[FSJNut]

Good idea. I'll take a good look at the vacuum lines.\nBut it seems like if it was a vacuum issue you would still have good pedal, just brakes that take both feet to stop. \nI'm wondering if I drove it on it's maiden voyage on one booster, and now the other one quit. It doesn't seem too likely that they would both quit at the same time.

[rcb]

True. How is the brake linkage between the pedal and the booster?