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MG 10-15-2004 15:23:40 141.156.38.199 11464 Report to Moderator	Recently saw a message posted about a Dodge 600 with brake problems and thought one of you guys might have an answer to my question. I have a 1974 Dodge 600 with remote mounted single stage MC and booster. My problem is that the brake pedal will seem to lock (become solid, no motion)intermitently as though I have lost vacuum to the booster (like what happens on a P/B passenger car with the motor off) and when this happens I have no brakes. As well, you may have to pump the pedal a couple of times to get the truck to stop. We have bled the system over and over, replaced the wheel cyls, master cyl on the firewall as well as the mc/booster combo under the truck. I am not familiar with this system and cannot seem to find any info on the system. I am also confused about the vent pipe off the remote mc which goes to a muffler or what looks like a air filter under the drivers seat. Any info would be greatly appreciated. [Reply]  [No Email]
Big Jim 10-20-2004 01:38:47 56.0.84.24 11487 Report to Moderator	Re: 1974 Dodge D600 Brakes in reply to MG, 10-15-2004 15:23:40   This is kind of a shot in the dark but I once worked on a GMC that was a few years older but had exactly the same symptoms. We found there was a check valve built into what looked like a brass fitting. The valve was leaking and the bypassed fluid ended up locking the hydrovac solid without any braking action.   [Reply]  [No Email]
MG 10-20-2004 11:37:00 209.150.117.98 11496 Report to Moderator	Re: Re: 1974 Dodge D600 Brakes in reply to Big Jim, 10-20-2004 01:38:47   Thanks Jim, Do not see a external check anywhere but I do believe that as Bob stated, the slave may be bottoming out because of all the pumping required to activate the brakes. Haven't had a chance to get back into it but it is a problem and all info is appreciated.   [Reply]  [No Email]
Dan 10-26-2004 11:31:11 4.226.144.49 11530 Report to Moderator	Re: Re: Re: 1974 Dodge D600 Brakes in reply to MG, 10-20-2004 11:37:00   Sounds like clasping brake lines which happens often with alot of older mopar products.   [Reply]  [No Email]
MG 10-20-2004 11:11:11 209.150.117.169 11494 Report to Moderator	Re: Re: 1974 Dodge D600 Brakes in reply to Big Jim, 10-20-2004 01:38:47   Thanks Jim, Do not see a external check anywhere but I do believe that as Bob stated, the slave may be bottoming out because of all the pumping required to activate the brakes. Haven't had a chance to get back into it but it is a problem and all info is appreciated.   [Reply]  [No Email]
MG 10-16-2004 07:52:38 138.88.195.170 11466 Report to Moderator	Re: 1974 Dodge D600 Brakes in reply to MG, 10-15-2004 15:23:40   After some reasearch I believe this unit is a Bendix Hydrovac or Midland Hy-Power. Would pumping the brakes exhaust the vacuum before it can recover and cause this problem? Maybe a vacuum resivoir would help. Also read that the brakes should still kina work even if the booster has lost vacuum as it is used just as an assist. An individual that has worked on the truck brakes in the past, told me the adjusters are worn out and he can't get the new shoes close enough to the drums. I believe this would cause the need for pumping but not the lockup in the pedal.   [Reply]  [No Email]
Bob 10-16-2004 11:07:26 66.163.134.177 11467 Report to Moderator	Re: Re: 1974 Dodge D600 Brakes in reply to MG, 10-16-2004 07:52:38   About the muffler/filter thingy... The booster runs on engine manifold vacuum. When vacuum is applied to one side of the diaphragm to "boost" the brakes, air is admitted to the other side. When you release the pedal, the process reverses, and the air is drawn out of the booster, into the engine. The filter keeps this air used by the booster, and ultimately fed to the engine, clean. Be sure the filter is clean and all hoses used on the vacuum side are rated for such use. I have seen people use heater hose, and it will collapse under vacuum, and cause a "hard" pedal. For the booster to work properly, you need to have the brakes adjusted so that the pedal firms up on the first application of the brakes, and no "pumping" of the brake pedal is needed to get the brakes to apply. If they are set too loose, or worn out, the piston in the booster is moved farther with each "pump" of the brake pedal, untill the booster runs out of piston travel, and then the brake pedal will be "hard". If the brakes have been "bled" thoroughly of air, and the adjusters can not be set up any more, to firm up the pedal on the first stroke, adjuster repairs, lining replacement, and possibly drum replacement are needed to get things back in spec., so the booster can do it's job. It probably won't be cheap, but driving with faulty brakes may turn out not to be cheap, either!   [Reply]  [No Email]
MG 10-18-2004 17:43:25 138.88.195.170 11478 Report to Moderator	Re: Re: Re: 1974 Dodge D600 Brakes in reply to Bob, 10-16-2004 11:07:26   Thanks BoB, I realize that there are some issues that need addressing. As you mentioned, air in the line, adjustment. Finding parts is a real chore as the truck is so damn old. I will see if I can get these things fixed and report back. I thank you for your input. What about converting to a dual stage booster/mc mounted on the firewall? I realize I will have to find a mc with the same volume, bore and stroke. But am I using the calculations for the slave or the master cyl mounted on the firewall? Thanks.   [Reply]  [No Email]