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Discussion Starter #1
I just purchased a new brake pressure gauge from British Tool Works.

This is the first time I’ve use a gauge like this. I wanted to be certain of my brake system #1 condition before going to the trouble of replacing the accumulator sphere.

As you can see in the video, there was no “flick-up” pressure. Apparently, in a healthy system, the gauge should quickly go right up to 1000 PSI. In this case, it only jumped to 400 PSI, and it took a full 30 seconds to reach 500 PSI. It finally peaked at 2,200 PSI after 1:30 minutes. There was some fall-back pressure and the gauge reading remained dead steady at 2,000 PSI.

I guess this means my nitrogen charge is very low and my sphere needs replaced?

Please shared your perspectives.

Many thanks!

 

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Yes, also send out the attached regular for rebuild.
 

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How is the other system? You may be in for another set. The brakes, when up to spec have authority..
You are going about this in the right way.
 

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You have got flick up pressure - it's 400 PSI. It shows the nitrogen is low. Have you carried out the brake pedal test? Everything else looks good.

Here's an except from "From the Shadows Corner"


The gauge should jump very quickly
to a reading of 1000 psi or lower.
This first indication on the gauge is
the amount of nitrogen in the sphere.
If the gauge goes to 500 psi and then
starts rising from there, that's the
amount of nitrogen in the sphere.
This is called flick up pressure.

Geoff
 

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There is flick-up pressure, but it's clearly low.

I agree that the brake pedal test would be useful additional data, but even if it isn't "right now" that accumulator is going to need either recharging and/or rebuilding.

For details on the brake pedal test see: SY Brakes & Hydraulics - Diagnostics & Maintenance
 

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Discussion Starter #6
I just finished the system #2 check. I pumped the brakes slowly and steady 200 times. The system #1 light came on at 35 pumps. System #2 light never came on! I must have a bad switch or bulb.

When I removed the nipple on the number #2 system to hook up the gauge, about 12 ounces of fluid came streaming out. I was surprised there was still pressure in the system after 200 pumps.

The gauge reading on the number #2 system was a surprise. The needle did not even move when I started the car (video below). It took about 30 seconds for the gauge to swiftly move up. It finally reaches 2000 PSI and then cycles up/down by a few 100 PSI as normal. Now the fluid levels were low so I not sure if this could be the cause of the delay in the pressure build.

What do you think?

 

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Pressure test must be done with sufficient amount of brake fluid in the reservoir. Your No.1 system would appear to have a way too low nitrogen charge in the accumulator sphere (as indicated by the low flick-up reading) but otherwise No.1 system seems close to normal limits. Your No.2 system would appear to have no nitrogen in the accumulator sphere as indicated by the absence of a flick-up pressure reading so the accumulator sphere definitely needs to be resealed and recharged or replaced but there's another issue in the system identified by the gauge needle fluctuating up and down like a fiddler's elbow. This would suggest that a valve is opening and releasing pressure when this shouldn't be happening and the pump is then having to work hard to replenish the pressure but the valve releases again as soon as the pressure attains a certain level. I experienced a similar problem on my No.2 system a few years ago and after some trial and error I narrowed it down to the height control solenoid valve releasing pressure because of crud at the valve seat. I temporarily plugged the fluid supply to the height control solenoid valve and disconnected the solenoid wires and then my gauge readings became normal. I am concerned about the high pressure discharge from your accumulator valve bleed screw after you had depressurised the system by pumping the brake pedal 200 times, this might also indicate a blockage problem in the rear suspension or a collapsed flexi hose at the rear trailing arm which causes a pressure build up that finds it way back to the accumulator control valve. It has also been known for rear callipers on the front brakes to bind as a result of pressure build up when there's a blockage in the rear. As a starting point in your investigation of the No.2 system I would suggest plugging the height control solenoid valve and see if that causes the gauge needle to desist from fluctuating up and down.
 

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Discussion Starter #9
This is incredibly helpful. Sounds like I need to get familiar with the rear height control system. I'll give your test a try and report back. Thank you.
 

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Another test you could do is replace the bleed nipple on the accumulator control valve and insert the pressure test gauge into the high pressure outlet of the accumulator control valve instead and see if you get a slightly higher pressure reading without those up and down fluctuations on the gauge needle. If that is the case you will know that the problem is farther down the line and my guess is the height control solenoid valve based on my similar experience. In any event your No.2 sphere is shot and should your engine stall you have no residual brake pressure on the No.2 system.
 

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There are couple points that i would like to make, given i worked on Shadows from'60's. Good practice is to remove hp flexible (next to bleed screw) outlet pipe from accumulator body after depressurising system of course! The no2 system does hold onto pressure through height control-even if light is on dash, again good practice is to bleed pressure from height control rams and vertically rock back end car up and down.
By inserting gauge in outlet pipe this isolates reservoir, pump and accumulator from rest of system in order to check it's integrity first, before looking for other issues (if there are any). On starting engine gauge should flick up to between 900-1000psi. As said, this indicates nitrogen pressure-anything below 750-800 requires attention. The purpose of this nitrogen is to give safety reserve of brake pressure to stop car safely if engine cuts out.
The pressure should then build steadily to around 2200-2300 psi and settle at 21-2200psi. I used to also remove reservoir return pipe (after clamping to make sure reservoir does not drain). I then put clear pipe on metal return pipe from accumulator body into same jar as bleed screw pipe. The purpose of this is to observe when the valve body started to return fluid to reservoir. In theory this should not start until about 2000 psi is reached. In reality fluid starts to bleed slowly at first at about 18/1900. If it is bleeding below this it normally is indication that the ball bearing that seals the return is pitted where it sits/seals on bobbin in valve block. If it is very bad, this means that every stroke of pump, instead of fluid going into sphere to charge system, it is being bled off back to reservoir. This accounts for very slow build up pressure-as in one post comment. By opening accumulator bleed screw slowly (so will need bleed pipe in jar) the pressure will drop.
If system working as spec at about 1800 the system that by transfers fluid pressure from sphere to just bleeding it back to reservoir should close, allowing pressure to build again to 2200psi-and so the cycle starts again.
Hope this helps a bit. Make certain reservoir is clean-especially gauze filters!
ALWAYS remove gear selector isolator when working in shop. So easy to knock selector.
 

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Good points Gordon, best to establish in the first instance that the accumulator control valve is operating as it should.
 

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Oh there goes another tool I need to buy so I can check all is well with my SS1.

I have a particular concern with the spheres of my SS1..

My father was a good engineer and rebuilt the spheres when he owned the car back in the 90's (before I inherited the car from him around 2010), and sometimes he was known to improvise (ex desert rat) ..

He did not have access to high pressure nitrogen, but did have access to high pressure oxygen.. Good engineer with metal and I will always love him for my early mechanical education. But potentially not a good engineer with chemistry though!

I have no proof he used oxygen, but I would not put it past him...Need to check they are functioning correctly before I drive it, and later need to check the spheres and diaphragm have not oxidised.

Off to send some more money to Kelly at BTW...
 

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Off to send some more money to Kelly at BTW...
Well, at least you know when you're buying from Kelly you're getting better-than-factory quality in many cases and OEM quality, at "worst," at prices far lower than one should have any right to expect in small-production custom tooling.

God Bless British Tool Works and Kelly Opfar!!
 

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Apparently, Brian and I are in a mutual admiration society. Brian's tireless research has added a wealth of knowledge to be available to our little party of nutcases - um, I mean enthusiasts. His willingness to help all of us and share his knowledge and resources for well over a decade should not go unnoticed.
I have Brian's resource lists and several other documents saved and several of them listed (and properly credited) on my own site.
Brian, is there a central repository where people can find all of your documents? I know I've seen all of them but I don't have them all saved.
Kelly

British Tool Works
 

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Hey Kelly, I will be sending you an email once I get a chance to look through the other items you make, as I do want the brake pressure tester kit, but also need to spend some time looking at other tools suitable for my car to join the carb tools that came a couple of weeks ago (very pleased with them)

Brian, to mirror Kelly's comments, is there a single repository for all of your documents? I would like to sit down for a read of them at some point.
 

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If you can find a copy of "The Shadow's Corner" by Cal West, buy it. It came out a long time ago and was sold by the club. I used to attend hands-on tech seminars by Cal, who was the RR-USA tech guy in the northeast. It covers many areas of the Shadow, problems, solutions, re-builds, etc.
 

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There was also a 3 tape VHS series that was factory produced covering re-builds of the hydraulics. Yes, I have a set and not for sale.
 

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Kelly & sarbirus,

There is no "single point" and definitely not "all my documents." They are spread across several Google Accounts and the Google Drives associated with same, and I have a lot more stuff I've put together over the years for posting on the forums that exist there, and in MS-Word documents on my own computer alone.

Now, on my computer, I do have everything I've ever touched related to RR/Bentley stuff under one folder, but that would take days to upload, and a lot of it was for private correspondence not meant for public consumption.
 
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