Friday, June 17, 2016

Leaking ABS modulators on 1990s Rolls-Royce and Bentley motorcars

By this juncture, wise owners of vintage Rolls-Royce and Bentley have learned to take fluid leaks in stride.  It’s part of the charm, to keep the garage floor lubricated.  Folks who could not handle the leaks bought Toyotas instead.

But we assume the leaks won’t strand or disable our cars.  We particularly assume the leaks won’t cause us to crash.  That is what makes this particular story so distressing.

The 1997 car shown here arrived at our shop with some common complaints.  The brakes were soft, and pulled to one side and the low fluid warning was coming on.  It seemed routine – add some fluid and bleed the nitrogen bubbles out of the system.  We encourage people to do this service every year, in the spring, because nitrogen gas leaks into the fluid slowly as the accumulators age.

But that didn’t solve this car’s problem.  Bleeding did fix the pull, but only temporarily.  A closer look revealed the problem.  The ABS modulator was leaking, allowing fluid to escape (hence the low fluid warning) and allowing air to get into one of the front brake circuits (hence the pull to one side.)

The fix for that was obvious – a new modulator.  That was when I had a rude surprise.  I went to the heritage.bentleymotors website and entered the VIN.  Then I typed “ABS modulator” into the search box. The part I was seeking came right up – the UR27685.  As is often the case, the website said, “dealer to advise on cost and availability.”  Unfortunately, the dealer found no cost, and no availability.  The part was discontinued.

I was rather surprised that Crewe would simply drop an essential part that’s used in most 1990s sedans.  But that seems to be the case.  A search online revealed it’s out of stock at the aftermarket sites too.  I hated to do it, but we went to the used parts people and got a “pre-owned” brake modulator.  It leaked too. 

With that we realized that some new solution was needed.  Fixing the leaking modulators is not an option, because they are assembled in a way that precludes disassembly.  The other issue is that repair parts are not sold.  That means anyone repairing the modulator would have to assume responsibility for testing and validating critical brake system components.

After considerable thought and document review, we settled on what we think is a better option – we changed the hydraulic plumbing to the configuration RR/B had immediately before the addition of ABS. 

The original Rolls-Royce hydraulic brake system was extremely complex – un-necessarily so, as it turned out.  They had two pumps pressurizing two reservoirs, and those reservoirs were pipes to two sets of distribution valves, lines, and brake calipers such that each wheel had two essentially independent brake systems stopping it. 

By the late 1980s the engineers at Crewe had quietly backed away from that in favor of a system where one hydraulic circuit powered the front brakes, and the other circuit powered the rear brakes and the level control.  The cars still had two brake calipers on the front wheels, but they no longer had two lines feeding them. Now they were fed with one circuit.

When you look at an older Rolls (like the Shadow in the top photo below) there are two completely independent circuits for each wheel.  By the 1990s (lower photo, Continental R) it looked the same superficially but the two calipers were now fed from one hose.

This was the hydraulic system RR added antilock functionality to in the late 1980s.  Returning the ABS-equipped car to that basic design turns out to be fairly straightforward.  The modulator has two “inputs,” from brake circuits 1 and 2.  It has outputs for the left and right front, and the rear.  It also has returns to vent excess pressurized fluid back to the reservoir when ABS activates. 

We made up a series of pipe adapters to take the place of the modulator.  The benefit of this is that we don’t have to engineer and validate something new.  We’re returning the car to the previous iteration of the Crewe brake design.  Given the choice of no ABS versus a system that leaks, becomes unsafe, and will eventually fail entirely, the choice is obvious.

And for most owners, the elimination of another $3,000 part that can fail is a welcome simplification.

As these cars age, it is certain that other parts will be discontinued and we will face similar situations.  The best we can hope for is to make wise choices and hope for simple modifications with good outcomes.  This appears to be such an example.

Thanks to vintage Rolls-Royce and Bentley master technician Bud Orlich for figuring this one out!

John Elder Robison

(c) 2016 John Elder Robison
John Elder Robison is the general manager of J E Robison Service Company, celebrating 30 years of independent Land Rover, Rolls-Royce and Bentley restoration and repair in Springfield, Massachusetts.  John is a longtime technical consultant to the Land Rover, Rolls-Royce and Bentley clubs, and he’s owned and restored many fine British motorcars.  Find him online at or in the real world at 413-785-1665

Reading this article will make you smarter, especially when it comes to car stuff.  So it's good for you.  But don't take that too far - printing and eating it will probably make you sick.

Wednesday, March 16, 2016

Diagnosing Raps and Noises in Land Rover Pushrod V8 Engines

How do you diagnose a liner or piston rap from a Land Rover engine? 

These are the most serious noises, because they call for complete engine teardown and rebuild.  Liner noises are often confused with valve train rap, and considerable time may be spent chasing a false trail.

Piston and liner noises sound similar but the setup and circumstances may differ.  Here are some videos where you can see and hear the difference.

Piston noises tend to come on gradually, with no noise at first and increasing noise as the engine warms up.  One good clue to a piston noise is that they tend to worsen under throttle, and go away if the plug wire is removed from the affected cylinder. 

The following video shows the piston movement and associated noise in a dismantled engine:


Piston rap happens when the pistons are too loose in the bore.  This was particularly a problem for the 2003-4 Discovery engines.  The pistons are usually tapered with more wear at the bottom. This taper causes a poor combustion gas seal at the piston rings, so motors with sloppy pistons may use oil, or have dirty oil.

Those things aside, piston rap is not fatal to the engine.  A truck with loose pistons may run for years, making gradually more noise.  We fix the problem with new flanged liners and new pistons.  The liners are honed to the exact size of the pistons and the rebuilt engine typically runs more smoothly and silently than it did when new.

Liner noises are different in that they often come on suddenly like flicking as switch, as the engine gets warm.  The engine will be silent, and then, suddenly, it raps so loud you think it’s coming apart.  Once rapping the liner noise is not affected by pulling a plug wire.  The noise may go away under throttle on the road, as combustion pressure jams the liner in place.

In a cold engine the liner is held tight by metal contraction.  As the motor heats up the aluminum block expands more than the steel liner, and at some temp the liner comes loose. That is when the rap starts.  That's why it has a sudden onset, and that sets it apart from gradually increasing piston noise.

The video below shows (in the center of the frame) the liner moving up and down as the crankshaft is rocked back and forth in this 2003 Land Rover Discovery 4.6 engine.  The noise in the video is what you hear when the engine is running, just louder.


Liners move when they were installed incorrectly.  In the manufacture of the motor the liner was supposed to be pressed into the cylinder bore until it seated against the step cast into the block. Then the liner would be cut off flush and countersunk.  Liners that are properly installed CANNOT move, because they are constrained at the bottom by the block casting and at the top by the head and head gasket.

After the liner moves for a period of time it will destroy the head gasket fire ring, and the engine will fail.  Until then, the truck will run fine.

Check out the photos of an original liner, and a flanged liner. We fix this problem by fitting new liners with flanges at the top, so they cannot move up and down.  The liner is clamped between the block and the head gasket and cannot move.  The fit at the bottom – where the original errors occurred – is no longer important.

The original Land Rover V8 liner, the one that breaks loose and moves (c) JE Robison Service

A flanged liner, which cannot move (C) JE Robison Service
Here is a closeup of an engine block, counterbored for flanged liners.  If Land Rover had taken this step to build a better quality engine, these failures would not be happening today.  Carmakers make all sorts of tradeoffs to same money, and this one is not working out too well 

Land Rover block, ready to fit flanged or top hat liner (c) JE Robison Service

In addition, the flanged liners seal against combustion gases getting into the cooling system through cracks in the block casting behind the liner.  This is another and more common cause of Land Rover engine failure.

As of this writing – Spring 2016 – the cost to bring a truck into our shop, rebuild the motor to address failures like this and repair the other issues common to a worn out motor costs $11-15,000.  When motors are rebuilt we can upgrade from 4.0 to 4.6 and we can balance and blueprint for greater smoothness. J E Robison has been doing these rebuilds and upgrades longer than any other shop in the USA, and we’ve seen a very good service record on the rebuilt motors.

The change to flange liners addresses a fundamental weakness in the engine, and renders them much less susceptible to future failure. To read more about liner issues and what we do to rebuild and improve these motors I suggest this essay from 2012

This article applies to all pushrod Land Rover V8 engines, including the motors in Range Rover Classic, County LWB, Discovery, and Discovery II.  It is not applicable to the newer L322 Range Rover, or the Range Rover Sport, LR2, LR3, or LR4.

Thanks to master technicians Paul Ferreira and Danny Ferrari for finding and figuring out these failures.

John Elder Robison

(c) 2016 John Elder Robison
John Elder Robison is the general manager of J E Robison Service Company, celebrating 30 years of independent Land Rover, Rolls-Royce and Bentley restoration and repair in Springfield, Massachusetts.  John is a longtime technical consultant to the Land Rover, Rolls-Royce and Bentley clubs, and he’s owned and restored many fine British motorcars.  Find him online at or in the real world at 413-785-1665

Reading this article will make you smarter, especially when it comes to car stuff.  So it's good for you.  But don't take that too far - printing and eating it will probably make you sick.

Friday, November 27, 2015

Recommissioning a Shadow-era Rolls-Royce or Bentley after long term storage

"It’s only got 25,000 miles on the odometer!  It’s been stored for ten-plus years!  It’s got to be in great shape, right?  How much will it take to put the car back on the road?  The seller only wants ten thousand dollars.  It's got to be a bargain, right?"

Quite a lot, in most cases.  This is the story of one of those cars.

1980 Rolls Royce Silver Wraith II (c) JE Robison

The late70s long wheelbase Shadows were badged as Silver Wraith II cars  (C) JE Robison

Jay’s Silver Wraith II arrived at Robison Service in the beginning of August, 2015. We saw a fairly clean-looking 1980 Silver Wraith II that had not run in some time.  The inspection sticker dated from the spring of 2007 – 8 years previously.  The owner believed the odometer reading of 30,300 was original.  The interior and mechanicals looked original; the body was repainted but clean and undamaged.  There was no sign of mildew or corrosion – at least where we could see. 

This was not a recent purchase.  It was Dad's old car, and now that he was getting on in years, his sons wanted to bring it to life for him to enjoy one more time.  That's often how these jobs begin . . . with a treasured old car from a parent or relative.  Other times we start with a purchase - a barn find.

We began this project by getting the car running (temporarily) and doing an evaluation of what we could see without a road test. The original fuel pump had failed and we had to make some modifications to install a new style pump from Bentley, because the current replacement unit uses entirely different line fittings and mounts.  The old Opus electronic ignition had failed in storage and had to be replaced. We identified a number of basic drivability problems that would have to be addressed before the car could be evaluated on the road:
- The owner was aware of inoperative brakes when he put the car in storage;
- We also found an inoperative parking brake;
- We found deteriorated fuel in the tank and corrosion/leakage at carburetors;
- There were a number of damaged rubber bushings in the front end that would lead to noise when driving;
- We saw collapsed brake supply hoses and aged hoses to wheels;
- All four tires were badly dry rotted.

We noted that the car was still a ways from being drivable and there could be other issues when it was on the road.  With an optimistic outlook, we set out to solve those major problems first.  The owner felt that most accessories had worked when the car was put in storage and he hoped they were still okay.

The first focus of our attention was the brakes, which did not work. There was no system pressure.  We replaced the supply hose to the front pump and tested the circuit. The front pump did turn out to be damaged, and we ordered a new one.  From there we moved on to the wheels.  We removed all six brake calipers and found rusted and frozen pistons in all of them. This is characteristic of a car that sat a long time without the required annual fluid flushes.  The cure is new pistons and seals.  The caliper bodies are generally usable once they are cleaned and honed, which we did.

When we took the calipers off we also examined the flexible hoses and found several of them were collapsing internally like the supply line. All appeared to be original and all were scheduled for replacement.  Rolls-Royce calls for these hoses to be replaced at the 8-year service interval but few owners do that.  In modern times, Land Rover and other carmakers have seen failures of 8-year-old brake hoses so the risk of failure is clearly real.

We pulled the combined accumulator/valve assemblies apart and found more rust and corrosion.  We tried to clean them, but in the end, the accumulator valve units were too corroded to repair and both had to be replaced.  Those valves are no longer available new so we sourced rebuilt units from the UK.  The accumulators themselves were rebuilt with new diaphragms and seals and recharged in our shop.  That was a bit of a challenge as the accumulators had been rebuilt at some time in the past and they were assembled incorrectly, so the factory holding tools could not be put in place.  We got them apart and they are assembled in correct alignment now.

We fitted new brake pads and retaining hardware once the calipers were rebuilt (most of the anti-rattle hardware was missing when the car arrived). The calipers were refitted to the car with new rubber hoses, and the parking brake calipers were rebuilt.  With this work done, we had proper functionality in one hydraulic circuit but the other pump continued to fail the test and we replaced it. With that done we had brake pressure in both systems. 

Moving on to the engine, we completed overhaul of carburetors and setup of the engine.  We drained the fuel system and refilled with clean gas, to find the gauge did not work.  The sender turned out to leak internally and we replaced it.  We replaced the aged ignition wires and mis-matched plugs, and repaired the distributor balance weights and springs which had been damaged by rusting in place. The bimetallic choke element was broken and we fixed that.  We tracked down and fixed a number of vacuum leaks and some under hood wiring errors that stemmed from prior vernacular repair efforts.  With that done the engine ran well.

The owner provided a set of Hankook tires which we mounted and fitted to the car.  The owner decided against fitting the original Avon tires due to the high cost and limited availability.  We have had good success with Hankook tires in the past.  The only issue we’ve seen is that the sidewalls are a lot softer than the Avon tires, and that makes for mushier handling.  However, that is not a concern for many owners of these cars.

We then turned to the transmission, which still had the original undercoating on the pan bolts, indicating the fluid had never been changed.  Inside we found a lot of sludge – no surprise with 35-year-old fluid.  We cleaned the valve body and pan, changed the filter, and filled with fresh fluid.  With the amount of sludge we found inside we have some concerns for the life of this gearbox, but there is nothing more we can do right now.

When we ran the car we measured normal brake pressure on our test gauge but the warning lights did not work properly.  We rebuilt the switches (a common job.)  The car was taken on its first road test and some issues were noted with the accessories.

The air conditioning system was empty; we charged it with the owner’s supply of R12.  The heat worked and the dash outlets worked when the Fascia switch was operated. Two windows were inoperative. We took apart both right side window motors and cleaned them up as best we could as new parts are no longer available.  We repaired broken wiring in the driver door and passenger front door for locks and windows.

The car was all over the road on road test so we replaced all four shocks and we also changed the bushings that had been rattling.  After review with the owner, we fitted Bilstein shocks front and rear; they are the most common choice for this type of car with a slightly more positive ride than the original units.

We continued to road test the car and experienced a loss of pressure on both brake hydraulic systems.  We traced that to one inch of sludge blocking the outlets on the bottom of the reservoir. We cleaned out that sludge and replaced the screens and seals on the reservoir. That remedied the loss of pressure when hot but we were still seeing contamination from the level control in the rear circuit. 

We took apart and cleaned the level control rams, valves, and lines. We removed quite a bit of gelled fluid from that last area.  When we did that work the rear level control began working (it had been inoperative.)  We were finally able to bleed it and eliminate most knocking noise from the rear.

After further running the engine oil and filter were changed.  The transmission was drained and filled again, and the rear axle fluid was changed.  Engine coolant had been changed in the earlier round of work (we drained it for the carburetor work) so all fluids are now fresh.  The fuel system is all clear; the tank was removed and cleaned and the outlet hoses were serviced as needed when it was out.  Some lines were changed on the motor; there are others that may need attention in the future.

All the running lights were checked and several exterior lights were repaired. Most of the light repairs were simple, but a few required tracing dead wire circuits back to the main distribution panel, and some hours were spent bringing the lights back to life.  One shock absorber ball joint was changed, and the compliance mounts were renewed in the front end.  With that done the car steered well and all joints are tight.  New carpet mats were laid into the passenger compartment and the trunk and battery tray was reassembled.  Interior detailing was not within the scope of this job, but the interior is complete and most accessories seem to be in working order.

The car is driving fairly well now.  It starts and runs well, and the engine is quiet.  There are no major fluid leaks at this time.  Steering and ride are normal.  Brakes are working properly though there is still some roughness from the brake rotors – which the owner elected to leave alone for now.  There is slight sag in the front and rear springs.  All in all, this car is now better than 90% of the Shadow II and Wraith II cars on the road.

Going forward, I recommend that the transmission fluid be drained and refilled next season.  The brake hydraulic fluid really needs to be changed on these cars annually and that should be done next fall (or in spring 2017) to protect the work we did on that system.  Other than that, future maintenance needs will be limited to issues that arise in use, and cosmetic fixing up.

I advised the owner to always use the highest-octane fuel he can get.  If the car is to be stored I actually suggest filling with aviation fuel as that does not have the ethanol that proves so destructive. These cars use Mobil Delvac engine oil, 15-40 or 15-50 weight.  The GM 400 transmission uses regular Dexron fluid.  The coolant is the traditional green ethylene glycol mix.  Brake fluid is a special RR363 product and that’s the only fluid you should use in that system.  I suggest putting the tires up to the maximum pressure for winter storage, and I recommend the rubber chocks from to preserve the tire roundness.

This job is typical of a comprehensive re-commissioning of a Shadow-era Rolls-Royce or Bentley motorcar.  We spent a bit over 200 hours on this project between August and November 2015. Our labor was divided among mechanical work, alignment and tire work, electrical troubleshooting, and cosmetic and detail work.  Most of the parts we needed were available, though no one vendor had them all, and the factory no longer supports many of the pieces we used.  When considering the time spent, remember we have lifts and all factory tools, and we have experience (some of us were trained on these cars when they were new!)  A hobbyist doing this at home would likely need considerably more time.

I hope this gives a perspective of what it will take to bring a long-stored RR/B back to life; this car was actually in better shape than many we see.  It’s worth noting that many of the major service headaches on this car could have been headed off by proper preventative care before the car was put away.  Sadly, that does not usually happen.  The best we can do is go through all the key systems step by step and bring the car to life in an orderly and efficient manner, knowing that we will still probably encounter unforeseen problems and complications. 

(c) 2015 John Elder Robison
John Elder Robison is the general manager of J E Robison Service Company, celebrating 30 years of independent Rolls-Royce and Bentley restoration and repair in Springfield, Massachusetts.  John is a longtime technical consultant to the Rolls-Royce and Bentley clubs, and he’s owned and restored many fine British motorcars.  Find him online at or in the real world at 413-785-1665

Reading this article will make you smarter, especially when it comes to car stuff.  So it's good for you.  But don't take that too far - printing and eating it will probably make you sick.