Re: Brake warning light.

["Al Powell" <APOWELL@agcom.tamu.edu>]

> 	Sure! But please explain in detail. Although I have the
> enthusiasm, my experience is little. Also, aboput the bomb. 
> I have tested the brake pedal and looks like my bomb needs replacement.
> Any instructions on that ?  (for some reason which is beyond me, I am
> not able to access the archives, even after repeated attempts)
> How safe is it to go for a secondhand bomb? Howmuch does it cost?
> If it's not much, I think I'll replace it b4 it gives up...

> Thanks,

> Vinod

Having a gauge made  is simple and will run about $40.  First, you 
must know the thread at the insertion point.  Your gauge screws in 
where the brake pressure warning switch is located - in the side or 
bottom of your brake servo.  

FYI - you WILL need a Bentley manual or copies of the appropriate 
pages from someone's Bentley to make sure you have the servo and 
switch positions, and especially to do the testing sequence.....

Usually the pressure switch are 1.0 pitch by 10 mm.  This sounds like 
greek but is familiar jargon to hose/hydraulic folks.  

To pull the warning switch, first turn the car off (let it cool so 
you don't get caught in or fried by the fan......) and PUMP the 
brakes 30 or 40 times to release all possible hydraulic pressure.  
Unplug both leads from the switch, then use an appropriate size deep 
well socket to unscrew it.  You will probably get a squirt of fluid 
when it comes out - so be ready and don't catch it in the face.  Hang 
a shop rag over the servo to catch the squirt.

Take the pressure switch to a hydraulic/hose dealer and have them 
make a gauge.  Here are the specs:

First, tell them what you're doing...it will help them understand 
what kind of gauge and hose you need.

1)  The gauge must be a hydraulic gauge rated for 3000 PSI service.  
(The system is rated to pump over 2200 PSI...)

2)  To the gauge, have them attach two to three feet of hydraulic hose rated for AT 
LEAST as much pressure as the gauge.  In my case, they used 5000 PSI 
hose, which is fairly stiff stuff.  Great.  I DON'T want it to bust!!

3)  IF you have a 1.0 x 10 mm fitting, unless they happen to have the 
right fitting (Not bloody likely....) have them use a 1/2" NPT 
fitting on the end of the hose.  This will NOT fit your car, but you 
can have it slightly re-threaded.

4)  Take the gauge tool to a machine shop and have them chase the 
1/2" NPT threads with a 1.0 x 10 mm die.  The threads are close 
enough that this works just fine.  ASk them to give you a good, solid 
copper washer which fits over the adapted fitting, as this will give 
you a base seal when you screw it into the brake servo.

5)  Go home, screw the gauge into the servo where the fitting came 
out, SNUG it down with a wrench (don't kill it, but get it good and 
snug...)

6)  Fire up the car, make sure you have no leaks, etc.  And run the 
tests as per the Bentley.  (Since I had adapted the threads on the 
gauge fitting, I wore protective goggles just in case the fitting 
blew.  I can stand tattoos but my eyes don't like 'em.  No problem, 
though - never leaked a drop!)

7)  When tests are completed, release pressure in the hydraulic 
system by pumping the brakes before removing the gauge and 
re-installing the switch.

This is not a mechanically difficult task.  Take your time and make 
sense out of what the Bentley says.  You can do all the tests except 
the flow test for the pump.

I no longer believe in used PAs.  Get a new one from a discount 
source.
Cheers...


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Al Powell                           Voice:  409/845-2807
Ag Communications                   Fax:    409/862-1202
107 Reed McDonald Bldg.             Email:  a-powell1@tamu.edu 
College Station, TX  77843-2112
W3 page - http://agcomwww.tamu.edu/agcom/rpe/alpage.htm

        "Give me a smart idiot over a stupid genius any day."
                 - Sam Goldwyn, movie mogul.
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