[DeTomaso] NO REAR BRAKES MANGUSTA

Edward A. Nauman enauman at adelphia.net
Sun Apr 1 14:50:21 EDT 2007


>Did a lot of pumping of the brake pedal, I could feel something when the
pedal went about two-thirds of the way down, there was also >a noise. This
happened every time I pumped the pedal.
 
My suggestion is that master cylinders are cheap.  I would just replace it
and be done with it.  I do have a suggestion to help alleviate the endless
pumping of the pedals (both brake and clutch) to bleed the system(s).  I
made a simple vacuum bleeder device that turns the job into a simple,
foolproof, one man job, that take less than 10 minutes to perform.  I used
an old fire extinguisher, small vacuum pump, ice maker type needle valve and
some vinyl tubing.  If you disassemble the valve on the fire extinguisher,
plug the gage port and adapt the exit nozzle port to the needle valve and
connect the appropriate tubing for the bleeder valves on your car, the only
thing that remains is to drill and tap a 1/8" NPT hole in the tank near the
top for the vacuum line to from the pump.  I also put a needle valve in this
line so I can close off the pump if I want to retain a vacuum in the bottle
with the pump turned off.  This prevents relying on the pumps check valve
when it is shut off.  If you add a second port to the tank for a shutoff
valve and a compressed air fitting, you can empty the tank by pressurizing
it and expel the fluid like the fire extinguisher was designed to do.  All
you have to do to bleed the breaks is:
 
1.)  Connect the line coming from the fire extinguisher's exit nozzle to the
bleeder valve on the car that you wish to bleed.  
2.)  Close the needle valve on the bleeder line.
3.)  Open the needle valve from the pump.
4.)  Start the pump and let the vacuum build in the tank.  
5.)  Open the bleeder valve 
6.)  Open the pump needle valve slowly and draw the fluid into the tank
along with the air in the lines.
7.) Close the bleeder valve on the car
8.)  Close the needle valves
9.)  Shut off the pump and go on to the next bleeder valve and repeat.
 
    Depending on how well your bleeder valve threads seal when the valve is
opened, it may seem that the air in the lines never seems to end.  This is
due to air being drawn into the bleeder line through the threads on the
bleeder valve.  This is not a problem since the air is drawn into the tank
and not back into the brake system due to the vacuum.  Just bleed a
sufficient amount of fluid from the system that constitutes a little more
volume than the lines can contain.  That way you ensure all the air in the
lines has been removed.  The only thing you need to watch is that the volume
in the master cylinder reservoir is not depleted during the process.  Keep
it topped off to avoid drawing more air into the system.  This is the
easiest way to bleed almost any hydraulic system without having to exercise
your thigh muscles while coordinating with the guy who normally opens and
closes the bleed valve.  It takes about 1/10 the time and works flawlessly.

 
    If you have an air compressor, you can buy a venture type vacuum pump
from Harbor freight for less than $10.  Add some cheap tubing and a couple
of inexpensive needle valves from your hardware store and an old fire
extinguisher and you are all set.  I made a light weight steel frame for
mine to mount everything on.  That way, the fire extinguisher handle serves
as a carry handle.  I also added a vacuum gage for convenience.  If you
don't have an compressor, there are a number of small compressors that will
work as a vacuum pump that you can find at garage sales etc.  Most of the 12
pumps sold as tire inflators will draw enough vacuum through the inlet to
work.  
 
    I made a larger version using an old garage size air compressor tank by
adding some wheels and a handle.  I used the venturi style pump on this one
so that I can siphon off flammable liquids if necessary without having to
worry about the explosion hazard created by motor brushes or pump friction.
I just vent the exhaust from the venturi outside to carry the fumes away.
If you want a picture or a schematic, let me know.
 
    Cheers,
 
Edward A. Nauman\
Senior Staff Engineer, Flight Test
Lockheed Martin Aeronautics
1011 Lockheed Way
M/S 0157
Palmdale, CA 93599
 
V: 661 572 7350
C: 661 305 7636
F: 661 572 3507
 
 
 
 



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