Silver Shadow Brake Issues: Your Help Would Be Appreciated! - Rolls-Royce and Bentley Forums
Reply
 
LinkBack Thread Tools Display Modes
post #1 of 25 (permalink) Old 01-07-2009, 02:37 PM Thread Starter
Member
 
wookieecantina's Avatar
 
Join Date: Jan 2009
Posts: 22
Silver Shadow Brake Issues: Your Help Would Be Appreciated!

Hello,
I recently purchased an extremely well cared for 1976 Silver Shadow, simply beautiful vehicle, but the brake 1 light is coming on while stopping and when brakes are applied slightly harder, the brake 2 light will blink but then stop. The brakes seem to be working fairly well, no noise, but the pedal is tad bit hard, not like a standard Shadow's brakes.
There is also a loud ticking coming form the engine near the distributor, so I'm thinking it could be a hydaulic pump.
Can't see any visual leaks, but perhaps a broken return spring is preventing adequate pressure from being built.
Any help would be dearly appreciated! I have a 1959 Cloud I and she's such a simple vehicle. This Shadow is very much a completely different vehicle but a true pleasure to drive.
Thank you for any assistance!

Dale
wookieecantina is offline  
Sponsored Links
Advertisement
 
post #2 of 25 (permalink) Old 01-09-2009, 04:55 PM
Senior Member
 
guyslp's Avatar
 
Join Date: Aug 2007
Location: Staunton, VA - USA
Posts: 2,919
Do you have the service records for the car?

The first thing that comes to mind based upon your description is that your accumulators are shot and need to be rebuilt. The fact that the lights both go out quickly suggests, at least, that the pumps are doing their job.

Here's the way to do a fairly exhaustive check of your hydraulic system and to isolate (in most cases) the source of problems:

-------------------------------------------------------------------------------------
Testing the Rolls-Royce/Bentley SY Series
[Shadow/T & Shadow II/T2] Hydraulic System

1. Make sure the system is *COMPLETELY* depressurized. The easiest
way to do this is to turn the key to the RUN position *without*
starting the car. Pump the brake pedal 50 to 70 times until the
Brake 1 and Brake 2 pressure warning lights come on. (If only
one warning light comes on after 70 pumps, you probably have
a bad pressure sensor switch for the system that hasn't lit. If neither
light up *both* are probably bad. That, or the lights themselves are
burned out, and you should know whether this is the case or not when
you try to start the car and the warning panel does its "light all the
lights to show you they're working" bit.)

This step is also a "quick test" of how your accumulators are doing
in terms of accumulating pressure. If the indicator light for either
system comes on in less than 30 pumps you can be almost certain
that the nitrogen charge in that system's accumulator is less than
1000 PSI and that the accumulator should be rebuilt. If the indicator
light comes on after less than 10 pumps, you may very well have
a ruptured diaphragm [which basically means that were the engine
to stall you have no brakes for that system almost immediately. NOT
GOOD.]

[To complete the "Quick Test",
AFTER BOTH LIGHTS HAVE ILLUMINATED:
1. Start your engine.

2. Observe your warning lights. They should go out after
10-15 seconds.

a. If a light goes out in just a second or two, it's
almost certain that you have a ruptured diaphragm
and the accumulator is being brought up to pressure
by being filled with fluid. If this is the case, YOU HAVE
NO BRAKING IN THAT SYSTEM IN THE EVENT OF AN
ENGINE STALL!!.

b. If they go out after longer than about 15-20 seconds
you probably have a depleted nitrogen charge.

IF EITHER a OR b is the case you need to have your
accumulators serviced. Circumstance 'b' is suboptimal
and circumstance 'a' is downright dangerous.

END QUICK TEST]


2. After you are certain the system is completely depressurized, slowly
turn and remove the bleed screw on the accumulator you are
testing and screw in a proper pressure gauge. Make sure that this
gauge has been used ONLY on RR363 based systems. Mixing even
the smallest amounts of RR363 and the later mineral oil hydraulic
fluid can create a BIG mess.

3. Start the car. In a PERFECT system:

- The gauge should quickly go right up to 1000 PSI. THis is
called the "flick up pressure" and directly relates to the
amount of nitrogen charge in the lower half of your accumulator.

- After the initial flick up the gauge should start rising higher
and higher until it reaches 2500 PSI and stops. This is called
the "cut out pressure".

- The gauge should then drop by about 100 to 150 PSI and then stay
steady between 2350 and 2400 PSI. This is called the "fall back
pressure."

4. Turn the car off. The pressure should now stay steady. If the pressure
drops at this point you have a leak somewhere in the system that could
be internal (some internal valve not closing when it should) or external
(a leaking o-ring in a valve somewhere. You may see dripping or, more
often, a "crust" has formed over time where there is a tiny, slow leak.)
If you've got a leak, find it and get it fixed before starting this whole
process again.

5. Start the car again and pump the brakes or activate the height control to
begin using accumulated pressure. The gauge should drop slightly each time.
When the decreasing pressure drops to between 1750 and 1850 PSI the accumulator
valve will open to begin pressurizing the system again. The pressure at
which the valve opens again is called the "cut in pressure."

6. The gauge will then begin rising, going back up to the cut out pressure of
2500 PSI then drop back down to somewhere between 2350 and 2400 PSI, the
fall back pressure. *ANY* loss of pressure if there has been no activation
of the brakes or height control indicates a leak *somewhere* in the system.

7. If there is a leak, you need to keep isolating the different components until
you find the problem.


Some examples of possible problems:

A) System is depressurized to 0 PSI, you start the car and the gauge rises
slowly and steadily to 2500 PSI, then falls back to 2350 and holds steady.
You turn the engine off and the pressure continues to hold steady:
YOUR ACCUMULATOR LACKS ITS NITROGEN CHARGE. YOU KNOW THIS
BECAUSE THE FLICK UP IS ABSENT.

B) System is depressurized to 0 PSI. Engine started and gauge goes quickly
to 600 PSI [flick up present, but low] then rises slowly to 1900 PSI and
stays there. Turn off the engine and the gauge slowly falls back.
YOU HAVE AN INSUFFICIENTLY CHARGED ACCUMULATOR AND A PROBLEM WITH
THE ACCUMULATOR PRESSURE VALVE.

C) System is depressurized to 0 PSI. Start engine and a quick rise on the
gauge to 1000 PSI [correct flick up] then steadily rises to 2500 PSI at
which point it settles bak to 2350 PSI [correct fall back]. When driving
the car you feel a clunking sensation that seems like a misfire (but you
know the engine isn't misfiring).
YOU ARE FEELING THE BRAKES ACTIVATE WHEN THEY SHOULDN'T. ONE
POSSIBLE CAUSE IS THAT THE SOLENOID VALVE THAT CONTROLS THE SPEED
OF HEIGHT CONTROL IS ENERGIZED AT THE WRONG TIME (CAUSING FAST
LEVELING BEHAVIOR WHEN IT SHOULD BE SLOW). MORE LIKELY, THOUGH,
IS THAT YOU HAVE A PLUGGED UP RESTRICTOR VALVE THAT'S CAUSING
FLUID BACK PRESSURE.

-------------------------------------------------------------------------------------

Good luck.

Brian

Brian

The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.
~ Niels Bohr


guyslp is online now  
post #3 of 25 (permalink) Old 01-09-2009, 06:39 PM Thread Starter
Member
 
wookieecantina's Avatar
 
Join Date: Jan 2009
Posts: 22
Thank You Truly!

Dear Brian,
I truly cannot thank you enough! You spent a great deal of time researching this topic and I'm so grateful for your assistance!
The widow we purchased this Shadow from could not locate any records, although she promised to mail them to us should they appear. She had a fellow who ran a limo business assist her in the care of the Rolls after her husband passed away and while he honestly seemed to care for her, he had his own mechanic complete much of the maintenance.
Judging by what you have stated, it does sound as though the accumulators are bad. The car levels and rides wonderfully, which sounds as though the accumulator 2 is probably not quite as bad as #1, but should be rebuilt also.
Wow, you have truly saved me a great deal of time, I can't thank you enough.
I'll try to pick up some gauges and diagnose a bit further. We have a shop nearby who comes very highly recommended but finances are a bit tight and being able to repair myself would be terrific.
Thank you again Brian, have a wonderful weekend!
Dale

Dale
wookieecantina is offline  
 
post #4 of 25 (permalink) Old 01-11-2009, 12:03 PM
Senior Member
 
guyslp's Avatar
 
Join Date: Aug 2007
Location: Staunton, VA - USA
Posts: 2,919
Reposted below with a few updates needed after several years have passed and more information has become available.

Brian

The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.
~ Niels Bohr


guyslp is online now  
post #5 of 25 (permalink) Old 03-24-2009, 08:47 PM Thread Starter
Member
 
wookieecantina's Avatar
 
Join Date: Jan 2009
Posts: 22
ALL FIXED!

Well, it took some time and a little money, but the tools to repair the accumulators arrived from the UK and after a very tiring weekend, both accumulators, both brake pressure switches and both accumulator valve body assemblies are now rebuild!
Thanks to Brian for his wonderful advice!

Dale
wookieecantina is offline  
post #6 of 25 (permalink) Old 10-23-2009, 11:45 AM
Phantom
 
Join Date: Oct 2009
Location: Kingston Upon Thames
Posts: 78
Blimey Brian, I could not have put it better myself.

And well done for overhauling the spheres they are a pain. I always had to wack the **** out of them before I could split them, even with the proper tool.

For the next time you can buy reconditioned spheres and valve bodys on an exchange basis.

Matt.

matt@introcar.co.uk

www.introcar.co.uk

Tel +44 (0)20 8546 2027
Skype Matthew_3
mattjdduncan is offline  
post #7 of 25 (permalink) Old 10-23-2009, 11:45 AM
Phantom
 
Join Date: Oct 2009
Location: Kingston Upon Thames
Posts: 78
Blimey Brian, I could not have put it better myself.

And well done for overhauling the spheres they are a pain. I always had to wack the **** out of them before I could split them, even with the proper tool.

For the next time you can buy reconditioned spheres and valve bodys on an exchange basis.

Matt.

matt@introcar.co.uk

www.introcar.co.uk

Tel +44 (0)20 8546 2027
Skype Matthew_3
mattjdduncan is offline  
post #8 of 25 (permalink) Old 10-23-2009, 01:26 PM Thread Starter
Member
 
wookieecantina's Avatar
 
Join Date: Jan 2009
Posts: 22
Wonderful Support From The Forum

This forum has been so exceptionally helpful during my Shadow education, thank you to all.
One thing I did notice on the accumulators, was the amount of torque required to split them. I purchased a 3/4 air impact, as in the Curzon video, but even at 100 PSI it was not enough. Then I realized my airline was only a 1/4 diameter, and it should have been a 1/2. Using a cheater pipe on a 3/4 drive breaker bar, the rings finally broke free. I'm actually 6'7, 290 pounds and it wasn't easy. This led me to believe that the last mechanic who assembled the accumulators probably used a 400 ft lb impact gun and tightened them purely with the impact gun, not a 3/4 torque wrench set to the specific required torque.
Just my impression and perhaps something to think about for those soon to take on this job.
I purchased a used 3/4 drive torque wrench on ebay for approx. $140.00 which was tremendously helpful.
Thank you again for your help and patience!

Dale
wookieecantina is offline  
post #9 of 25 (permalink) Old 10-23-2009, 01:53 PM
Phantom
 
Join Date: Oct 2009
Location: Kingston Upon Thames
Posts: 78
When ever I used to overhaul the accumulators I used to remove the caps, depress the valve to ensure no gas left in, thenI would lay the sphere in its side on an anvil and hit the ring with a 4.5 lb hammer. I would have to hit it very hard several times before I was able to split them.

When doing them back up I would put the valve together in the top, fit the new diaphram, then I put the two halves together and spin on the ring, As the torques are about 400 lb ft we would use a 2 meter scaffolding bar and hang on it. They have to be tight as they hold such high pressure.

Any way well done for doing them

Matt

matt@introcar.co.uk

www.introcar.co.uk

Tel +44 (0)20 8546 2027
Skype Matthew_3
mattjdduncan is offline  
post #10 of 25 (permalink) Old 10-05-2011, 06:25 PM
Senior Member
 
guyslp's Avatar
 
Join Date: Aug 2007
Location: Staunton, VA - USA
Posts: 2,919
FYI, to anyone following this thread, rebuilding accumulator spheres requires a special set of tools and is not, generally, a DIY job. If you can get access to the tools to disassemble the accumulator spheres and a nitrogen tank and the connection to charge them it is possible, but not an easy job.

You definitely need a very, very solid workbench to attach one part of the accumulator-splitting tool to and, often, will need two people to get sufficient torque to open the accumulator. When reassembling it, be sure to use some anti-seize compound on the threads to make it easier for the next person who has to rebuild them.

The accumulator rebuild kits (a diaphragm and a few other assorted bits) are to my knowledge available available exclusively from Crewe original parts suppliers. These days that means an authorized Bentley dealer.

There are several people in the U.S. who rebuild these accumulators. If you want an extensive list of resources for parts, repair, restoration, etc., then click on RR & Bentley Parts, Repair, Restoration & Other Resources Compilation on Google Docs to download the file.

If you are doing this job you should also plan on flushing and bleeding your entire hydraulic system. This is easier to do than one might expect. Take a look at SY Hydraulic System Flush & Bleeding Instructions for specific step-by-step instructions.

Brian

The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.
~ Niels Bohr


guyslp is online now  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Rolls-Royce and Bentley Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome
 

Garage Plus vBulletin Plugins by Drive Thru Online, Inc.

SEO by vBSEO 3.6.1