| Author | Message | ||
     Chris Miller Prolific User Username: cjm51213 Post Number: 122 Registered: 5-2013 |
Hi Folks, My master cylinder circuit is probably air-ridden which "disables" it and that is not unintentional right now, and not part of my question. The brake pedal travels almost to the end of its range before engaging the brakes, and that is just horrifying. You can only imagine. I can still lock 'em up, if I have a mind to, but I think I want to move the active segment closer to the beginning of the pedal travel range; maybe have it somewhere in the middle instead of the very end. Is this something I can adjust? Where can I find the instructions? Thanks for the help, Chris. | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 1221 Registered: 6-2006 |
the pedal acts on the master cylinder. When the master cylinder stops travelling it then operates the distribution valves. Fix the master cylinder and the brake operation range will be correct. Fit a slightly bigger master cylinder for less travel. | ||
| Chris Miller Prolific User Username: cjm51213 Post Number: 124 Registered: 5-2013 |
Hi Paul, Thanks very much. I was under the mistaken belief that the master cylinder was "driver feedback only". I will fix this and thanks for the help. Chris. | ||
| Bob uk Unregistered guest Posted From: 94.197.122.71 |
The master cylinder works one pair of pistols in each rear caliper this gives about 20% brakes and must be working Don't drive on public road until it is The master will stop the car without the pump pressure eventually (Message approved by david_gore) | ||
| Jonas TRACHSEL Frequent User Username: jonas_trachsel Post Number: 51 Registered: 2-2005 |
Shooting at the rear calipers will not help to stop a car. Pistols will eventually stop a car, if you shoot the driver. Jonas  | ||
| Chris Miller Prolific User Username: cjm51213 Post Number: 128 Registered: 5-2013 |
Hi Folks, I did bleed the master cylinder circuit with surprising results. One side showed no sign of air and the other side showed minimal amounts of air, meaning one "brake, open, close, release" cycle expressed two or three bubbles. I probably executed 20 bleed cycles, and that was all I found, but that tiny amount of air must have been in a really important place because this did completely restore the brake pedal active range to something more normal. Now I'm interested to see if the master cylinder is working sufficiently well to stop the car. Will this work? Go to an unused road that has a slope and park at the top. Turn off the engine. Brake until the red warning "No Pressure" lights come on, which effectively eliminates the power brake system. Shift to neutral, coast for a bit, and apply the brakes. At any point, if I see trouble, I can start the engine and will have power brakes quite shortly. Any problems with this procedure? Thanks for the help, Chris. | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 888 Registered: 6-2009 |
Chris, No, NO, NO!! The only brake system (if you ignore the parking brakes, which I am, or the miniscule braking from the master cylinder) in this car is the power brake system. Once your pressure warning lights are on, particularly if you've given multiple pumps after they've initially illuminated, you have no functional brakes!! There is still some residual accumulator pressure when the lights initially come on, which can power the brakes until you exhaust it, but why on God's green earth would you want to risk it! The master cylinder is not sufficient to stop your car once it's on a "real roll" and it would be foolish to try. As far as bleeding goes, the best method for the master cylinder circuit is to use a vacuum bleeder (or a positive pressure bleeder, but then you need to design a reservoir cover [or caps] that holds pressure during the bleeding process). Brian | ||
| Chris Miller Prolific User Username: cjm51213 Post Number: 129 Registered: 5-2013 |
Hi Brian, Thanks. I was going on Bob UK's observation that the master cylinder is sufficient to stop the car ... eventually. There appears to be some disagreement about this. So, now I'm curious to find out, if I can find out without putting anything at risk. I'm thinking an empty parking lot some evening... Find a gentle slope... Nobody around... Probably aught to be sure that the parking brake is working up to spec, huh? I don't have a vacuum bleeder, so I have to rely on manual techniques with the assistance of a surrogate driver. These may not be as good, but they work, right? As an aside, since I am fresh from an exhaustive analysis of the accumulators, I can say with confidence that the pressure warning lights on my '72 indicate "zero pressure", not "minimal pressure". I learned this when I was bench testing my rebuilds. I don't know if this is adjustable, and I didn't look, but I did take note. My circuit would open, effectively extinguishing the light, before even overcoming the initial pressure of the nitrogen, meaning zero fluid in the accumulator. I thought that it was not the right design goal, and I would have preferred them to warn me of an impending failure, rather then identify an exiting failure. Thanks for the warnings, Chris. | ||
| Geoff Wootton Grand Master Username: dounraey Post Number: 439 Registered: 5-2012 |
Hi Chris I had exactly the same idea. It would be really interesting to know just how much of a braking effect the master/slave system had on the car. My plan was to find a deserted road with a slope followed by the a slight uphill section and then roll the car when I was absolutely sure there was nothing else around. Purely for the sake of curiousity. I can absolutely recommend buying a hand operated vacuum pump for bleeding the master cylinder circuit. Saves having to get a helper and standing the car on it's front bumper. They are only about 30 bucks. Geoff. | ||
| Bob uk Unregistered guest Posted From: 94.197.122.84 |
According to my information The master developes 22% And at a guess over 1000 psi So it will be interesting to see if the lp circuit will stop the car Vacuum bleeder Vacuum cleaner Plug suction pipe with wood plug with hole in middle to suit 10 mm plastic hose 1 gallon cider glass jar Drink cider wake later Wood plug two 10mm holes One hole goes to vacuum cleaner The small pipe in this hole goes 1 inch into jar The other hole goes to bleed nipple and the pipe goes to bottom of jar The jar must resist collapsing due to vacuum If a lathe is available then easy Laboratory suppliers sell bungs I use this for not only brakes Power steering and radiators Pressure bleeding is possible but the tank has two vents so if is awkward 2 psi max pressure Work shop are 80/120 psi So use car inner tube not in wheel and Schrader valves My car has pistols not pistons because my predictive text knows better than me (Message approved by david_gore) |
