Mineral Oil Accumulators for Rolls Royce & Bentley from 1980 onwards

Matt covers all you need to know about Rolls Royce & Bentley models with hydraulic systems using mineral oil.

“Hi there & welcome back! Today we are going to talk about hydraulic spheres again. We’ve previously talked about the Rolls-Royce Silver Shadow spheres that take the RR363 Brake Fluid. In 1980 Rolls Royce & Bentley introduced the Mineral Oil Hydraulic System. They change from using RR363 and they begin to use a mineral oil. That was with the introduction of the Rolls Royce Silver Spirit and the Bentley Mulsanne, also the Corniche and the Bentley Continental. They went over, I think, slightly earlier. The same principle with the hydraulic sphere.. this is the CD6000GMF, this is the one for the brakes. It does the same job as the sphere on the Rolls-Royce Silver Shadow where there is a diaphragm inside, high pressure gas on one side and that stores pressure when you start pumping fluid into it.

So that’s like the battery of pressures, the reserve of pressure for the hydraulic system. There are two of these, two systems so you have got the two brake pumps still; the two valve bodies; two spheres, obviously the valve body is different. This is more like a standard Citroen setup – it’s very similar to a Citroen setup. But the pressures are different in the sphere. So you can’t just go and buy a Citroen sphere and bolt it on because you won’t get the right pressure in the system. You won’t get the right flick-up pressure. I think these are a 1000 psi which is the same as the Silver Shadow ones, or 900 and something. Basically, the same as this, which is the GMF1106, now this is the rear gas springs. These screw in above the rear suspension struts and they do a completely different job. The way the height control works on the mineral oil cars is that they have a hydraulic ram which is also your suspension damper and unlike the Silver Shadow where they have a normal damper and then a ram above it, which actually lifted the suspension separately, these have the damper which is hydraulically pressurised to give you a different height.

So, above the damper, if you obviously just had that damper with pressurised oil in it you are going to get a lock, the suspension is just going to lock up, but what this allows for is that pressure is actually acting on the diaphragm so this is an actual spring. This screws into the valve body on top of the damper and when the suspension goes up and you push the telescopic damper up, it pushes the fluid into this and against the pressure behind the diaphragm.

It’s got a completely different pressure to the CD6000GMF. This is a much higher pressure and I think if you were to put one of these in place, the suspension is just going to go solid because it won’t to be able to move the pressure inside the sphere. There are actually two different types: an early and a late one. They change them but you can actually interchange them, there is no real difference in pressure. It’s GMF1039, both of these take the same O ring. They screw in and the fitting is the same. Ooops, lost it!

So this sits in a recess inside the valve body. When you fit this what you can risk doing is actually you get it near the end and the O ring will just slip out of the recess, as it’s quite a shallow recess, and then instead of compressing the O ring you’ll actually pinch it and then high pressure fluid is just going to pour out. So these ones are a bit more fiddly because they are up in the boot so you have to take the boot trim out and gain access to them that way. Obviously de-pressurise the system before you touch them, but then, when you are spinning this on you can just about get them in. Just got to remain careful that you don’t misplace the O ring as you screw it back up.

You can usually get them off with a pair of big plumbers grips, but if they are tight sometimes people air chisel them off but then you risk damaging other parts on the car; eg. the valve body. But apart from that, these are just straight forward and replaceable. You can throw them in the bin or recycle them. But they are not something that you can actually overhaul, there is no diaphragm you can get there as you can see. They are welded shut and permanently capped off, not like the shadow one that you can dismantle and rebuild. That’s pretty much it. If you have any questions, please comment on the video and we will try to get back to you with the right answers.”

PhotoPart NumberDescriptionApplicationPrice (excl. VAT)
GMF1225-X seal o ringGMF1225-XACCUMULATOR O RINGRolls-Royce Silver Spirit & Silver Spur
Bentley Mulsanne, Brooklands & Turbo
GMF1106-X accumulatorGMF1106-XSPHERE REAR SUSPENSIONAll models from 1980 to 2003 with chassis 13860 onwards£64.01
CD6000GMF-X accumulatorCD6000GMF-XSPHERE BRAKE ACCUMULATORAll models form 1965 to 1980 with chassis 50,000 onwards (mineral oil)
All models from 1980 to 2003
GMF1039-XGMF1039-XREAR GAS SPHERERolls-Royce Silver Spirit & Silver Spur
Bentley Mulsanne & Turbo

Check the RR – Technical Video Library for more.

Tags: , , ,
Posted in RR Technical - Rolls-Royce & Bentley
Pin It

Comments are closed.