Joined: Thu Mar 22 2007, 08:13AM
Location: In the workshop
Posts: 1063
There is no need whatsoever to say sorry, Pietin. One of the things that I love about this forum is that free speech is allowed...not like on another forum I used to be on!
Joined: Wed Apr 23 2014, 06:51AM
Location: SF Bay Area, California
Posts: 2
Has anyone experienced gradually increasing/accumulating rear brake line pressure? I upgraded my 1966 300 (power, all drum system) as recommended above but the described problem resulted. I shortened the pushrod and de-adjusted the rear shoes to no avail. I've now installed an adjustable proportioning valve on the rear line (and should only be getting 30% pressure to the rear). Still no dice. I also started with all new wheel cylinders, hardware, and drums. I've bled the master and all four lines. The problem starts after I've driven around town for a few miles and just gets worse; the rear shoes start dragging and the drums get hot. After parking for 20 minutes, the pressure subsides and I can drive again for a few miles. This is driving me crazy. Any help will be greatly appreciated. Thank you in advance. Feel free to call me as well. 510-396-5915 Bob (Richmond, CA)
Joined: Thu Mar 22 2007, 08:13AM
Location: In the workshop
Posts: 1063
On my '65, there is a spacer between the firewall and booster. Could it be that you need one? Without it, the brakes are always slightly on.
As Mike66 mentioned earlier (and I misread) a prop valve is not needed with a drum/drum set up. If you must use something like that, use a combination valve. They can easily be altered for drum/drum, and then changed again if you ever decide to fit front discs.
One other thought. Is the m/c one with a single bore, or concentric bores?
Joined: Sat Aug 19 2006, 05:03PM
Location: Ontario, Canada
Posts: 2919
I suspect that the rubber brake line between the frame and the differential needs to be replaced. When they age they can actually start to swell-up inside and close. You can push fluid past them to apply the brakes, but then they hold the brakes on!
This has happened to both front lines on my dad's 1978 Oldsmobile and one front line on my '66 Chrysler convertible. Never had it happen to a rear line, but if it did, what you're describing would be the result.