It is often said that one of the reasons for the sweetness of the Derby Bentley is that all the parts function together perfectly to deliver the car's remarkable driving qualities--and that when one part fails to function properly, the whole car suffers. One reason that the parts function well is that a great many of them are lubricated through the Bijur system. It follows, then, that a key to the sweetness of the Derby Bentley is the proper operation of the Bijur system.

Many articles have been written, in The Flying Lady, Spectre, and elsewhere, on rebuilding the Bijur system, the Bijur plugs, and the Bijur pump. These articles are uniformly good, and the information they impart is vital. However, all of them miss one small but vital part--as I found out the hard way when rebuilding the Bijur systems on both B196HK and GWN20, only to have oil leak out all over the floor from GWN20.

It seems that there aren't drip plugs regulating oil flow through the Bijur system to all parts of the front axle and front wheels on the Derby Bentley (and Phantom and Small Horsepower Rolls-Royces). There is just a straight flow of oil that is only shut off when the bottom of the plunger in the Bijur pump descends to the bottom of the pump housing and forms a seal. Sometimes the plunger doesn't form a good seal, and in consequence the oil flows to the front axle, to the front wheels, down the backs of the front wheels, and onto the floor. The trick, then, is to ensure that a good seal is formed. And this is the little bit of information that I have never seen in one of the aforementioned articles.

At the end of the plunger is a leather disk. It is a bit over 1" in diameter, and it is made of a piece of leather that is about 1/8" thick. It is kept supple by the oil in the reservoir. However, if the car is laid up for a number of years, without any oil in the reservoir, the leather disk at the end of the plunger will dry out, become quite brittle, and be useless in making a seal in the future. It is surprisingly easy to replace the leather disk, and you can actually do it while the reservoir is still on the car. You have to contort yourself a bit, use a mirror and a good light, and use a dental pick, but you can do it. I've done it now on both B196HK and GWN20.

First, extract all the oil from the reservoir. Then undo the piping and fittings at the bottom of the reservoir and remove the metal cup. With a little perseverence, you will expose the bottom of the plunger and the dried-up leather disk. Use a dental pick and a strong light, and probably a mirror, to extract the leather disk from the metal flange on the bottom of the plunger that surrounds the disk. Get a piece of 1/8" thick leather from a shoe store; don't try to use that extra bit left over from when you recovered the seats, because it will probably be too thin. Cut a new leather disk from the shoe store piece. Refit it to the end of the plunger, carefully pushing it in at the circumference under the metal flange. Make sure it is a good fit and lays flat. Refit the cap, reassemble the fittings and piping, refill the reservoir, bleed the system, make sure everything works, and hit the road in your Derby Bentley. Your car will thank you, as will the spirits of W.O., Sir Henry, Lord Hives, Harvey-Bailey, Robotham, et. al.

Philip C. Brooks (7/11/97)