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Discussion Starter · #1 ·
I need to replace the seals in both hydraulic pumps, and also the inboard master cylinder. Is there a preferred method for bleeding the system, such as using a vacuum pump? Which I will buy if necessary.

It looks like maintaining the correct level of mineral oil within the tank might be the most "annoying" thing to do, because of the need for the special bottle and the difficulty in seeing the actual level.

Any wise words of advice before I start this project?

Thank you.
 

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You do not need a vacuum pump. There is no master cylinder on these cars. Bleeding is thoroughly explained within the factory workshop manuals which are available online for free.
 

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Discussion Starter · #4 ·
You do not need a vacuum pump. There is no master cylinder on these cars. Bleeding is thoroughly explained within the factory workshop manuals which are available online for free.
Thank you. OK, "reservoir", but referring to it as a mater cylinder is not entirely incorrect. Both contain the supply of hydraulic fluid.

That aside, I have the bleeding instructions, in the ASSIST software, but I have read posts by people who have had difficulty bleeding the system. So, there is a valuable knowledge base out there, which would be helpful.

Thanks again.
 

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Which car is concerned ?
Personnally I have used for more than 20 years a more simple method, inspired from the workshop and from R-R / Bentley specialists.
Engine on as described on the document Brian put , and with something between steering wheel and brake pedal to keep it down.
I start to bleed the 2 brake pressure switches, then one by one the the 8 brake bleeders .
1 per caliper in front, so 4 bleeders in front
2 per caliper ar rear ( 1 up, 1 down, sometime on the frame) so 4 bleeders

With ABS the order should be for LHD : left then right front wheel, left then right rear wheel.
You are supposed to go from close to ABS unit to far.

I regularly check and adjust level, after each wheel

I do not touch suspension which blleds automatically

In any case, LHM should be replaced about every 6 years, specially in calipers.
Yours might be brown if old.
 

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Discussion Starter · #7 ·
Which car is concerned ?
Personnally I have used for more than 20 years a more simple method, inspired from the workshop and from R-R / Bentley specialists.
Engine on as described on the document Brian put , and with something between steering wheel and brake pedal to keep it down.
I start to bleed the 2 brake pressure switches, then one by one the the 8 brake bleeders .
1 per caliper in front, so 4 bleeders in front
2 per caliper ar rear ( 1 up, 1 down, sometime on the frame) so 4 bleeders

With ABS the order should be for LHD : left then right front wheel, left then right rear wheel.
You are supposed to go from close to ABS unit to far.

I regularly check and adjust level, after each wheel

I do not touch suspension which blleds automatically

In any case, LHM should be replaced about every 6 years, specially in calipers.
Yours might be brown if old.
Oops, forgot to include the vehicle information. 1992 Silver Spirit.

Thanks for the advice. So, fluid is pumped through the bleeder nipples by the engine pumps. But, at what rate? does it trickle out, or so fast that I would have to quickly move back and forth between the bleeder and the reservoirs to keep them topped up?

Also, because there are two calipers on the front wheels, are both bled at the same time, or one before the other?

Thanks again for your advice.
 

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There are 2 circuits..read about the system beforehand. At 2400 psi it will definitely squirt. Do not overtighten the bleeders.
 

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Paul,
Fluid is pump from the 2 LHM tanks by pumps then sent under pressure to the caliper.
With my system you do bleeder by bleeder, with the other system, I think better to be two.

As Wraithman says, make sure to understand the system before touching it.

Each caliper has its own bleeder.
4 Front caliper have one bleeder per caliper = 4 bleeders
2 Rear caliper have 2 bleeders per caliper = 4 bleeders

Read carrefully my text. I said 8 bleeders for front and rear calipers in my first message

Each bleeder need tt be bleeded
 

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Discussion Starter · #10 ·
There are 2 circuits..read about the system beforehand. At 2400 psi it will definitely squirt. Do not overtighten the bleeders.
Yes, thanks.

I have read through the system info, and the ASSIST bleeding instructions, which calls for bleeding both systems at the same time. First both calipers on both front wheels, along with the high pressure switches and the pressure limiting valve. 7 bleed points at once. Then the right rear wheel, and lastly, the left rear wheel. The ASSIST procedure also calls for opening the next bleeders before closing the lines just bled. I can see the sense in the latter, but it does result in having 11 tubes and jars connected at one time.

The procedure seems easy enough, except that trying to look at air bubbles on 7 lines, for the front section, means that I will probably waste mineral oil on 6 lines before the 7th is bubble free. Plus, bleeding 7 lines at once will drain the reservoirs pretty quickly. So, from that standpoint, a modified Jean7's method makes more sense. First, both pressure switches, followed by both front left calipers, then both front right, followed similarly by the rear wheels.

Here's another issue. The brakes are slow to engage and slow to release, taking approx 1 second to respond after pressing the brake pedal. Both front and rear brakes. 1 second doesn't seem like much, but it result in more foot pedal pressure than necessary being applied. Based on your experience, do you have an idea which component in the system is likely to cause the delay?

Thanks again.
 

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Discussion Starter · #11 ·
Paul,
Fluid is pump from the 2 LHM tanks by pumps then sent under pressure to the caliper.
With my system you do bleeder by bleeder, with the other system, I think better to be two.

As Wraithman says, make sure to understand the system before touching it.

Each caliper has its own bleeder.
4 Front caliper have one bleeder per caliper = 4 bleeders
2 Rear caliper have 2 bleeders per caliper = 4 bleeders

Read carrefully my text. I said 8 bleeders for front and rear calipers in my first message

Each bleeder need tt be bleeded
Thanks Jean7.

Please see my reply to Wraithman. I will likely follow your method, but modified to do both systems at once.
 

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You most likely have air in the system and it is compressing before it works the brakes.
How can you properly bleed brakes if many bleeders are left open when the point is to bleed air out of the system, one at a time and systematically remove the air, usually starting from the farthest bleeder, RR.
 

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Discussion Starter · #13 ·
You most likely have air in the system and it is compressing before it works the brakes.
How can you properly bleed brakes if many bleeders are left open when the point is to bleed air out of the system, one at a time and systematically remove the air, usually starting from the farthest bleeder, RR.
I did not consider air in the system because the brakes do not feel spongy. Also, air in the system should not cause a delay in the release of hydraulic pressure. There must be a valve hanging up somewhere, of a restriction in a line that feeds both front and back wheels.

I understand you disbelief of that bleed method. Like you, I've always bled one wheel at a time, using the conventional method, and sometimes using automatic bleed nipples. But, this is my first time with an accumulator based system. The bleed method I described come from ASSIST, which is a Rolls Royce/Bentley publication, so I figure the method is correct. What I didn't include was the little detail that the bleed nipples are opened with the engine off and after the system has been depressurized.
Starting the engine results in the pumps attempting to pressurize the system, but with nipples open, the system should not be able to achieve full operating pressure, but will be enough to force hydraulic fluid through the system at a flow rate that, hopefully, is not too high.
 

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1 second before action/reaction is a lot for brakes.

Bleed as much as you can, I would say air and probably dirty LHM.
Also, if I were you, I would take all padds out and clean with a fine iron brush all the calipers inside (carrefull with seals) to make sure the padds can move freely.

One important point, when you open brake pressure switch, you do not need to push the brake, but you need engine iddling. Often this is where this is air because this is a one way point with no circulation.

Second very important point, open all bleeders very slowly, otherwise you will get emuslion, meaning bubbles, which is bad.

Last imprtant point, do not overtighten bleeders otherwise they will leak.

I know well procedure from workshop you refer to and decided not to follow it and bleeded only switches and All calipers bleeders.

To be done next year if your LHM apperas very dirty, otherwise every 6 years max because LHM is "suffering" indeed in the suspension system because of pressure and huge efforts on oil.
 

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The brake pedal won't feel spongy with air in the system because it is operating a distribution valve, not compressing fluid in a master cylinder. Delayed application and release of the brakes is a sign there is definitely air in the system. Bleed one at a time, it's way too complicated to try and do all at once with a number of jars and hoses. One jar, one hose, start at left front, work to rear. Run engine 4 or 5 minutes, shut off, use a stick between seat bottom and pedal. Bleed fronts, top up fluid, bleed rears, if fluid flow stops run engine again to build up pressure. Keep an eye on reservoir floats but you should be able to do both fronts and rears with only a single top up of reservoirs unless the fluid is brown in which case you should clean the reservoirs out and start with fresh mineral oil.
 

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Discussion Starter · #16 ·
Excellent information from Wraithman, Jean7, Jim Walters and guyslp. Thanks guys.

Obviously, the operating condition and problem symptoms with this RR system are quite different compared to the standard systems that I have worked on. Quite an education.

I have to service both pumps, both leak, particularly the rear one, which sits above almost a 1/2 inch deep puddle of LHM. I also have a leak on the inboard reservoir, so will also be servicing that one, maybe both, especially as the "clear" tubes are not clear enough to clearly see the black level indicator.

Thanks again.
 

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I got the original "shortened and simplified" bleeding instructions years ago from a RR/Bentley expert by the name of Richard Treacy who used to be very active on the RROC Australia Discussion forums as well as the RROC US counterpart. He seems to have dropped off the face of the earth as far as either of those venues goes, but is apparently still running his parts business in Australia:

SpurParts Pty Ltd
33/56 O’Riordan Street, Alexandria, Sydney, 2015
New South Wales, Australia
[email protected]
A.B.N. 52 161 984 247


His original comments were:

All that stuff in the manual about low-pressure and high-pressure bleeding and all over the place is B****cks, It is mainly to scare of the uninitiated, but introduces many silly and unnecessary risks. Almost every service specialist I know does it the way I describe. To quote one in my hometown “these cars have the easiest brakes on earth to bleed.”.

The same applies to SZs. Forget all the intermediate bleed points. If you just do it properly at the end points (callipers and struts) that does the job more safely, quickly and easily.
 

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I got the original "shortened and simplified" bleeding instructions years ago from a RR/Bentley expert by the name of Richard Treacy who used to be very active on the RROC Australia Discussion forums as well as the RROC US counterpart. He seems to have dropped off the face of the earth as far as either of those venues goes, but is apparently still running his parts business in Australia:

SpurParts Pty Ltd
33/56 O’Riordan Street, Alexandria, Sydney, 2015
New South Wales, Australia
[email protected]
A.B.N. 52 161 984 247


His original comments were:

All that stuff in the manual about low-pressure and high-pressure bleeding and all over the place is B****cks, It is mainly to scare of the uninitiated, but introduces many silly and unnecessary risks. Almost every service specialist I know does it the way I describe. To quote one in my hometown “these cars have the easiest brakes on earth to bleed.”.

The same applies to SZs. Forget all the intermediate bleed points. If you just do it properly at the end points (callipers and struts) that does the job more safely, quickly and easily.
I completely and unequivocally endorse both Guyslp's and Richard Treacy's advice regarding SY and SZ brake system bleeding having both done this on DRH14434 during my custodianship and the numerous self-help workshops we organised for members of the NSW Branch of the RROC[Australia] and two Federal Rally sessions I conducted as the Federal Registrar for the Silver Shadow series especially those wishing to undertake routine servicing of their vehicles,

I made great use of a Shadow brake system interactive model created by a Norwegian RR/B owner Tord Sambal which I highly recommend for all DIY owners of SY and SZ vehicles wishing to understand how the hydraulic brake and levelling system on these vehicle functions. A copy of this simulator cannot be attached below as executable files are not allowed, I thank Tord for giving me permission for his model to be freely made accessible world-wide for all SZ and SY custodians and I am happy to provide the simulator programme to any member of this form if they send an email to me at [email protected]. If you have any concerns about this link, I authorise Guyslp to verify my authenticity and status on request.
 
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