Inspecting Rolls-Royce and Bentley hydraulic systems

How to test and inspect the brake and hydraulic systems in Shadow and Spirit/Spur era Rolls-Royce and Bentley motorcars.

Disclaimer: This article describes a process whereby a knowledgeable owner can get a good approximation of a car's hydraulic system condition in the field without specialized test tools.  It is not meant to replace the procedures described in the factory workshop manuals. Rather, it recognizes that the workshop manual procedure relies on specialized hydraulic gauges which are unavailable to most owners around the world, and the need to test brakes is more widespread than the proper tools to do it.

1983 Corniche drophead (C) JE Robison

The advice in this article is provided as-is, with no warranty as to completeness.  I've done my best to illustrate a complete procedure but there are inevitably circumstances where a car might experience a hydraulic problem that would be missed by this simplified test, yet found by the factory procedures.  Always use the gauge tests if you can  

One of the more unique features of 1965-1998 Rolls-Royce motorcars is the hydraulic system.  The hydraulic system powers the brakes and the rear suspension’s height control.  These systems are legendary for their complexity and potential for bank-breaking repair costs.  In this essay I'll show you how to check yours out so you can get a sense of what's happening before disaster strikes, and hopefully avoid disaster altogether.

The early version of this system (1965-80) is filled with a derivative of conventional brake fluid (RR363).  RR363 is essentially brake fluid with an added lubricant.  The lubricant is needed for the engine driven pumps. Newer cars (until the advent of the Silver Seraph series) used Castrol hydraulic system mineral oil, or HSMO, which by its nature lubricates the pumps and powers the brakes.  The two fluids are not compatible.  Use of the wrong fluid in a car will cause severe system damage.  All reservoirs are clearly labeled RR363 or HSMO.

RR363 fluid reservoir as used from 1966-1980.  Note warning label and style - a simple steel container, normally painted silver as shown.  Windows to check fluid level are visible on the side.

Mineral oil reservoir (and fill bottle) from a post 1980-Rolls (1995 shown) Style varies by model year but colored warning and symbols are the same. Floats to indicate fluid level via a green dot are visible atop the reservoirs.

The fluid in these systems should be changed annually.  Some owners question the need for this, when their cars are rarely driven.  Here's why it needs to be done:  The hydraulic pumps deliver fluid to accumulators where they compress nitrogen gas under very high pressure.  The fluid is separated from the nitrogen by a rubber barrier, but it is inevitable that some nitrogen will make its way into the fluid.  This forms bubbles, and bubbles in the fluid cause the brakes to pull and act erratically.

Any car that has been sitting a long time is sure to have "funny feeling" brakes for this reason  The cure:  Change the fluid annually.

The system contains two hydraulic circuits that operate in parallel for the brakes.  One of the systems also powers the rear height control.   Hydraulic fluid is stored in reservoirs on the left fender well.  Lines carry the fluid to the hydraulic pumps, which are located in the center top of the engine; under the carburetors or the fuel injection.  High-pressure pipes carry the hydraulic fluid to the accumulators under the motor.  From there excess fluid is returned to the reservoirs.  Braided lines carry the high-pressure fluid to the distribution valve assembly located under the driver seat. 

Rolls-Royce brake distribution valves (all Shadow and Spur era cars similar) under driver seat

A network of steel pipes carries hydraulic fluid to the calipers at each wheel and to the rear suspension and height control.   The rear suspension contains height control valves, shocks, and gas springs that sit above the shocks in the trunk area.

All the pumps, valves, and moving parts are subject to failure.  Calipers rust or leak.  Gas springs and accumulators lose their gas charge.  Metal lines rust and rubber hoses deteriorate invisibly.   A system this complex can only be fully tested by trained people using special tools in a workshop.  However, it’s possible to do a pretty good “quick check” without tools, using the following procedure:

Begin with the vehicle sitting, engine cold.  We start by discharging the hydraulics. Get in the car and slowly but steadily pump the brake pedal 25 times.  Open the hood and check the level in the hydraulic reservoirs. (see illustrations above)  If the level is low, look for leaks (as evidenced by wet spots on the calipers, the hoses, or the engine pumps or accumulators) Turn the key on but do not start the engine yet.  You should see two lights illuminated, identified as Brake 1 and Brake 2.  Depending on the year of the car these may be in an electronic unit between the gauges, in a group of lamps to one side, or by themselves in the middle of the dash.

If you do not see the lamps, or if only one is lit, give the brakes 10-20 more pumps.  If the second light does not come (or if neither come on) on you can assume that warning circuit is broken.  That is a big red flag.  A car whose brake safety lamps are not working is not safe to drive, as it could have total brake failure with no warning. To proceed with testing, start the car.  Watch how long it takes for the lights to go out.  They will typically flicker briefly before extinguishing. If one or both lights do not go out you probably have one or two failed pumps, which is a no-drive fault.  If the lights remain on more than 20 seconds the hydraulic pumps are probably weak.  That's not a no drive fault but it indicates the need for professional inspection and probably service.

Run the car 2 more minutes, shut it off, and turn the key back on.  Begin slowly pumping the brake and note how many pumps before the Brake 1 and 2 lamps illuminate.  If you see the lamps come on (either or both) in 5 pumps of less, the car is not safe to drive.  If the light comes on within 5-10 pumps the car should be driven carefully straight to the workshop. Less than 20 pumps indicates the car has weak accumulators and should be serviced soon.

You want the car to endure 20+ pumps without either light coming on.  That indicates a system with sufficient charge to provide a margin of safety in braking, particularly if the engine stalls at highway speed or on a hill.  If you do not get to 20 pumps before seeing a lamp, in each case, the repair needed would be to replace (Spur) or rebuild (Shadow) the accumulators and overhaul the valve bodies.  After that the system would be bled.

** MAKE SURE THE CAR IS IN A SAFE PLACE FOR THE NEXT TEST.  It may lunge and roll when put into gear.  Be sure nothing is at risk for damage or impact **

Now, while holding the pedal down at the 20th or 21st press, start the engine.  Immediately pop the car into gear - get it in gear within a second or so of starting.  What does the car do?  If it lurches forward and then stops in a few seconds as the brakes grab, there is a problem in the warning circuit.  If the car holds firm and does not move the brakes and the warning lamps are ok, and it's good.

If the car holds 21 pumps the brake accumulators should be good for a few more seasons.  Brand new accumulators may hold 40 or more pumps but any number in that range is safe.  If you want to know the exact count, run the car till the lights go out, give it a few more minutes, and slowly pump till both lights illuminate.  Usually one will come on followed by the other.

Once that is done, let the car run and wait for the brake warning lights lights to go out.  Go to the back of the vehicle and bounce each corner.  If the car is soft and pushes down a few inches with your weight that’s normal.  If it’s rock-hard that is a sign of failed gas springs in the rear suspension.

Sit down on the rear bumper (even better, have two people sit on the bumper) and wait 30 seconds. You should feel the car lift to the original (and visibly correct) ride height.  If it does not lift that’s a sign of problems in the height control.

Take the car onto the road.  Try braking slowly and quickly.  Pay attention to any pulling or diving that may indicate caliper problems or air in the lines.  Look for any pulsation or shudder that may indicate warped or damaged rotors.  Let the car come to a stop on a gentle slope and release the brake.  Make sure the vehicle begins rolling smoothly and the brakes do not drag.

Shut the car off and put it in neutral.  Press and release the brakes a few times.

Finally, put the vehicle on a lift and make sure all four wheels spin freely.  If any wheels drag that may be a sign of caliper trouble.  Next check all the components for leakage.  Look at the reservoirs (top left fender well), the pumps (top of the engine), the main valves and accumulators (under side of the engine), the distribution valves (under driver seat), the brake lines and calipers, and the rear suspension components.

   

Look at the fluid and make sure it looks smooth and uncontaminated.  RR363 (used 1965-1980) should be almost clear; HSMO (used 1980-1998) is dark green.  There should not be any foam, sediment, or sludge visible.  Color should be consistent. 

Look at the rubber hoses to see if they are original.  If your car is more than 10-15 years old I suggest you replace all rubber hoses as they can swell inside, creating invisible failures.  A swollen hose may cause brakes to drag and overheat.  Old hoses are also prone to bursting.

Original Shadow-era brake hoses, overdue for change (C) JE Robison

New style lines and hoses in a restored Shadow (C) JE Robison

If your car passes all these tests you can give yourself and the vehicle a pat on the back.  If you see potential failures, I suggest you find a specialist and get a more thorough evaluation.


If you liked this story, please leave a comment.  And if you want more . . . here are some of my other RR/B essays


Thoughts on buying a used Rolls Royce or Bentley - applies to Silver Cloud and newer series cars

More thoughts on Spur - Spirit - Turbo era car buying

Thoughts on restoration - applies to all cars

Evolution of the RR/B models - Silver Shadow through Arnage/Seraph - original article from the Robison Service website

Inspecting a Rolls Royce or Bentley - Applies to Corniche, Continental, Azure, Turbo R, Mulsanne, Eight, Turbo R, Silver Spur, Silver Dawn, Silver Spirit

More Things to Look For in a 1981-2000 Rolls Royce or Bentley - this is the original article from the Robison Service website

The last Crewe built Rolls Royce convertibles - applies to 2000-2002 final Series Corniche

Repairing convertible top hydraulics - Applies to 1996-2004 Rolls Royce and Bentley Corniche and Azure cars

Head gasket failures in Bentley Turbo cars - applies to Turbo R, Continental R and T, Azure, Arnage

Checking engines after head gasket failure - Applies to all cars

Checking and inspecting Rolls Royce hydraulic systems - all cars after Silver Cloud and print to Silver Seraph. Applies to all Shadow/Spur era vehicles

Case Study - brake failure in a Shadow - Silver Shadow era cars with RR363

Rear suspension gas springs - Applies to all 1981 - 1999 cars prior to Silver Seraph

Changing batteries in seat and ECUs, Applies to 1980s-1990s Silver Spirit / Silver Spur / Mulsanne /Eight / Turbo R

Changing alarm ECU batteries,  Applies to 1980s-1990s Silver Spirit / Silver Spur / Mulsanne /Eight / Turbo R

Servicing Shadow and Spur series brakes - applies to 1966 - 1999 cars after Silver Cloud and prior to Silver Seraph

Alcon racing brakes for Continental and Azure - Applies to all 1990s cars but most particularly to the final series Azure, which had these brakes fitted at the factory - a unique variant

Fixing Power Steering Leaks - applies to 90s cars with the reservoir above the alternator

Questions and answers on collector car storage - Applies to all cars

Evaluating paint - Applies to all cars

John E Robison

JE Robison Service

RROC Tech Consultant

Robison Service has provided independent service, repair, and restoration for Rolls Royce and Bentley owners all over New England for over 25 years. Our company is an authorized Bosch Car Service Center. We also service Mercedes, Jaguar, Land Rover, Porsche, and MINI motorcars. We have flatbed transport throughout the region. We also offer local pickup and delivery for cars in  Springfield, Wilbraham, Longmeadow, Agawam, Westfield, Northampton, and Amherst.