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dovaka · 06-16-2013, 02:47 PM

I have been working on this RV for a bit and I am in the process of completely restoring it from the ground up. i went to bring it to the gas station the other day to fill up the tanks after finally getting it to run well and realized that it had no brakes. after poking around for the cause i saw that the master cylinder was empty so i filled it up and tried to bleed out the air so i could figure out why it had drained but it would not build nay pressure at all. so i started looking further and found what appears to be a brake booster mounted to the frame rail in the middle of the rv. there are 2 of them and one of them is missing a cap on the bottom where the 2 larger hoses go into it. i suspect this is the issue thats not allowing pressure to pass threw but i cant seem to find a replacement unit or maybe i just need a new cap on the bottom which resembles a freeze plug.
anyone else out there have this same type of rv or brake booster setup?

Skip426 · 06-18-2013, 11:04 AM

Started working for Dodge in 75 and can say that I only saw this set up a couple of times and never had to work on it. Most times I was under the coach to replace plugs and wires that had a tendency to burn up.
If there is a cap missing at one of the vacuum connections then that may have been a contributing factor to poor running condition. Have you checked the area of the missing cap with the engine running.

If you've lost a master cylinder's worth of fluid , you've got a leak , and if you haven't already replaced the wheel cylinders , I'd say that they would be the next item on the restoration list.
Also move the master cylinder forward off it's mounting , lines should flex enough to move an inch or so, and look for fluid leak there too.
BTW. Welcome to iRV2. looks like you have a real project on you hands.

Dave78Chief · 06-18-2013, 12:45 PM

First step is to determine what Dodge chassis (M300, M400, M500, M600) and year 75/76 you have to define what braking system you have. Dodge had a few different setups. You will need the Dodge VIN number to do that. Many coach mfg's installed this years body (i.e 76) on the previous year Dodge chassis (ie. 75). Though my first hunch is you have a M400 with Hydro-VAC boosters Dave's Place - M400 (RM350) 1973-75. They may need to be rebuilt. You have to bleed these systems in stages.

Rear brakes should be the Twinplex (http://dave78chieftain.zxq.net/TwinplexBrakes.html) but maybe Duo-Servo (http://dave78chieftain.zxq.net/BXDuoServoBrakes.html)

Many of the brake parts are available through NAPA. With this chassis, having the service and parts books is a must. Most parts are found by cross referencing the Dodge P/N to the aftermarket number.

Dave

http://dave78chieftain.zxq.net/DodgeRBrake.html