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Discussion Starter #1
Hi to all My rolls Royce silver Shadow 1971 brake problem
Brake light 1 turns on every time pedal is pressed I have switched around the pressure sensors made no difference check the hydraulic pump and they're both pumping but the pump closest to the radiator is pumping erratically the actuators' were rebuilt last year need help please
 

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Assuming that you have sufficient hydraulic fluid in the front section of the reservoir and that the reservoir filter isn't blocked and causing fluid starvation to the No.1 pump my first thoughts would be of a ruptured diaphragm in the No.1 accumulator sphere or a defective No.1 system accumulator control valve which is not allowing sufficient pressure to build. The easiest way to find out if the problem is in the sphere or accumulator control valve or hydraulic pump is to attach a hydraulic pressure test gauge to the bleed screw on the accumulator control valve to monitor what the pressure readings are. Another possibility is that the push rod that operated the No.1 pump via the engine cam has snapped rendering the No.1 pump inoperative, a hydraulic pressure test at the accumulator control valve will help to narrow down the problem. Basically the only way to diagnose the problem without stripping down components is to use a hydraulic pressure test gauge, without a test gauge you're only shooting in the dark and could be bringing extra work on yourself. There's an article on this site about building you own hydraulic pressure test gauge or you can purchase a quality one at a very reasonable price from Kelly Opfar at Britishtoolworks in Utah. If you google "Silver Shadow bleeding your brakes the easy way" written by Brian Vogel you'll find an article on building a hydraulic pressure test gauge. Good luck.
 

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found the PDF for building the gauge by googling "building your own hydraulic pressure gauge - Rolls Royce" but I reckon that the gauge supplied by Britishtoolworks works out just as cheap and is less hassle considering the effort to source the various assortment of threaded components.
 

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Discussion Starter #4
Ok thanks for you help will go get a pressure gauge to test I did do a test with the brake pump by undoing the top screw to see how much brake fluid will come out it was coming out erratically and where would I find the accumulator control valve to thanks
 

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Ok thanks for you help will go get a pressure gauge to test I did do a test with the brake pump by undoing the top screw to see how much brake fluid will come out it was coming out erratically and where would I find the accumulator control valve to thanks
If you follow the steel outlet pipe from the No.1 brake pump it will lead you down to the accumulator control valve on the lower side of the engine. You say that your hydraulic pump is expelling fluid erratically, therefore the problem would appear to be within the pump itself or with the fluid supply from the reservoir to the pump. If the pump is working efficiently it should deliver a steady pulsating flow. Check that your reservoir filter isn't blocked with crud which would restrict the fluid supply to the pump. Also check the gravity feed hose between the reservoir and the pump for obstruction. If you depressurise the system and detach the lower end of the high pressure hydraulic feed pipe from the pump at the accumulator control valve (ACV) and place the end of the pipe in a suitable clean container you should get a steady pulsating flow of fluid into the container once you start the engine, it should pump about a half pint per minute. If there's an air lock in the pump this method should bleed it. If that does the trick you will need to refit the pipe to the ACV and bleed all the No.1 system brakes afterwards. Is the No.1 pump noisier than the No.2 pump? Be careful when rethreading the pipe to the ACV, it's easy to crossthread these fittings, first loosening the top end where it leaves the pump may help when reattaching the lower end of the pipe to the ACV inlet. If the pump has a good gravity supply and is not air locked but still doesn't work properly then it will need to be removed and serviced or replaced, there's a special tool for removing it which is also available from Britishtoolworks. You can view or download the technical manual for your car for free on the Australian RR forum site. I suggest that you study the manual to familiarise yourself with the hydraulic system, the system is not as daunting as it might first appear once you get to understand it. Good luck.
 

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I would open the reservoir first and see what's inside. Drain with a turkey baster and inspect the filter screens after removing with a 1" deep socket. I think you may find destroyed screens.
 

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Discussion Starter #9
Cheers I check the filters inside the reservoir they still look brand new though replace last year I will have to check the gravity fed hose tomorrow thanks for all your help
 

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Discussion Starter #10
Number one pump is noisier it also has a clicking sound sometimes but haven't heard it in a while ever since the brakes went spongy and brake light come on
 

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It's possible that the pump has a bent or snapped push rod, the fact the pump was chattering before the brake pressure light illuminated but became silent afterwards might indicate this. Before going to the trouble of removing the pump (for which you will need a special tool) try the hydraulic fluid delivery test at the lower end of the high pressure pipe at the ACV. If fluid delivery is OK then reattach the pipe and do a hydraulic pressure test at the ACV. If fuid delivery is sporadic or insufficient and you end up having to remove the pump and push rod read the manual first because there's important information there about measuring the thickness of the shims between the base of the pump and the engine.
 

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The use of a hydraulic gauge that can read 0-3000 psi and glycerin filled, will tell you the complete story at several points within the hydraulic system.
All is good with having the correct diagnostic tool, however understanding the results, is another matter, and fully explained in the workshop manual.
 

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I will also add that there is way too much made of the pumps "being noisy" when it is eventually determined that the charge in the accumulator is close to or entirely spent.

The pumps are designed to operate, at least during the charging phase, with some "push back" on them from the nitrogen charge in the accumulator. Much like many things of that ilk, the push back acts to quiet them down a bit.

On both my cars the pumps have a very slight tick even when the system is "in perfect condition" but when the charge in the accumulator for a given pump has gotten low that ticking becomes distinctly more pronounced.

I have yet to hear anyone claim that the pumps are ever dead silent, at least when you're standing over the engine bay. I can hear them even in the car, just as I can hear the ticking of the SU fuel pump before starting as it primes the carbs or the whir of the Pierburg pump when doing same (but the latter never stops, since it runs continuously and the fuel is shuttled back to the fuel tank when the carbs don't want it - the SUs cycle on and off and there is no fuel return).
 

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I will also add that there is way too much made of the pumps "being noisy" when it is eventually determined that the charge in the accumulator is close to or entirely spent.

The pumps are designed to operate, at least during the charging phase, with some "push back" on them from the nitrogen charge in the accumulator. Much like many things of that ilk, the push back acts to quiet them down a bit.

On both my cars the pumps have a very slight tick even when the system is "in perfect condition" but when the charge in the accumulator for a given pump has gotten low that ticking becomes distinctly more pronounced.

I have yet to hear anyone claim that the pumps are ever dead silent, at least when you're standing over the engine bay. I can hear them even in the car, just as I can hear the ticking of the SU fuel pump before starting as it primes the carbs or the whir of the Pierburg pump when doing same (but the latter never stops, since it runs continuously and the fuel is shuttled back to the fuel tank when the carbs don't want it - the SUs cycle on and off and there is no fuel return).
I agree that a noisy pump isn't necessarily a problem but when there's no pressure warning light when a pump is noisy and then the pump goes unusually silent in tandem with the pressure warning light illuminating logic would make one wonder if something has gone wrong with the pump. A pump output test and accumulator pressure test would help to diagnose what's going on.
 

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All possibilities do need to be considered. That being said, I go for those that are easier to test for and/or more probable to determine the order I'm checking.

I would expect a dead pump to result in a circuit never being able to build up enough pressure to extinguish the warning light. If there was ever a period when the filter screens were compromised, the gravity feed hose needs to be checked to make sure that nothing has collected in it and is acting much like an embolism in the human body can.
 

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Discussion Starter #17
Hi mate thanks for that the brake light only comes on when the pedle is pressed and it turns off with pedle retracts
 

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Discussion Starter #18



Here's a video of the top of the brake pump is the push rod going up and down all right thanks
 

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that looks like it's travelling up and down as it should but that's all that the video will confirm, however, brake fluid should be belching out when you turn over the engine unless the fluid supply has been blocked or disconnected.
 

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You can download the workshop manual - TSD2476 - for free from the Australian RR forum or the Bentley Heritage site. Section G explains the operation of the hydraulic system.
 
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