Doing Your Actual Hydraulic Pressure Readings

Danger Warning #1:

If you see the gauge going to 3000 psi or higher, “STOP” the engine, have the vehicle carried to your local RR&B mechanic and warn them that the pressure is 3000+ psi when running, a defective accumulator relief

valve can exceed 3000 psi and explode with enough force to break the engine block!

Danger Warning #2:

Before connecting the gauge, even if you pumped down the system this morning, "if the system is still closed", pump your brake pedal slowly to drain system pressure again until both of your pressure warning

lights have illuminated (plus about 10 more pumps), "safety comes first, second and third" with this system.

Note: I install the 3000 psi pressure gauge in place of the hydraulic system accumulator bleeder screw.

Danger Warning #3:

“STOP”, Before Removing/Disconnecting the gauge from the system, even if you pumped down the system this morning, "if the system is still closed", pump your brake pedal slowly to drain system pressure again

until both of your pressure warning lights have illuminated (plus about 10 more pumps), "safety comes first, second and third" with this system.

Danger Warning #4:

“STOP”, "ALWAYS" assume that someone has started the vehicle while you were away from it, "if the system is still closed", pump your brake pedal slowly to drain system pressure again until both of your pressure

warning lights have illuminated (plus about 10 more pumps), "safety comes first, second and third" with this system.

You must NEVER use a test gauge on an RR363 system that has been used on a mineral oil system and vice

versa. If you happen to be a “mixed garage” where there are cars with RR363 and mineral oil systems

then you need to have TWO SEPARATE TEST GAUGES.

 

Testing the Rolls-Royce/Bentley SY Series [Shadow/T & Shadow II/T2 & Derivatives] 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. Slowly & Gently pump the brake pedal until the Brake 1 and Brake 2

pressure warning lights come on, usually 50 to 70 times. (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 back 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.