Accumulator sphere replacement - Rolls-Royce and Bentley Forums
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post #1 of 25 (permalink) Old 04-30-2008, 06:27 PM Thread Starter
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Accumulator sphere replacement

I want (need) to replace the spheres on my accumulators. I've done the brake pedal pump test, and can only get 12 pumps before the warning lights come on. This is not a good situation. I understand that 30 pumps is a minimum and 60 pumps great.
Anyway, has anyone got a feeling which spheres to use. I reckon that I can fit normal Citroen CX type spheres (as these are the correct era) on the accumulators. As for the rear suspension ones, (assuming I go the whole way), I need to get proper RR ones, as I understand they are set to a special low pressure (~18 Bar), which is not available 'off the shelf' for the citroen.
Also, does anyone know what the difference is between the Citroen XM and the CX accumulator spheres?

Cheers... Rob.

Red to Red, Black to Black, Blew to bits.
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post #2 of 25 (permalink) Old 04-30-2008, 10:32 PM
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Just had mine done and I confess that I took it in as the pumps were leaking as well.

Phil Garey
Santa Clarita
1985 Spirit
1967 MGB
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post #3 of 25 (permalink) Old 05-01-2008, 04:58 PM Thread Starter
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Re: Accumulator sphere replacement

Forgot to mention, its an 89 Turbo R.
Now then
I've had a look underneath (and looked in the manual). It seems that it is necessary to 'remove' the forwardmost (front I guess) accumulator unit to even stand a chance of unscrewing the sphere from the rear accumulator.
Do I have to remove this. or can I just undo it and move it out of the way a little to get the sphere removal tool on it and the sphere actually off.
Any ideas here?. I don't know if my situation is tighter than in the Spirit, as these items would have been on the other side of the block. My problem is the turbo, which has resulted in a possibly more cramped installation on the left hand side of the block.
Anyone any experience doing this?

Cheers... Rob.

Red to Red, Black to Black, Blew to bits.
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post #4 of 25 (permalink) Old 05-02-2008, 04:47 PM
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Hi Rob!

There is a good HOWTO available on the Australian forum. I've seen and read it but can't tell you the exct link. I'm afraid you will have to start your own search. I'll come back here in this thread, if I should run across this the coming weekend.

Regards JimKnopf

from Munich, Germany
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post #5 of 25 (permalink) Old 06-04-2008, 10:41 AM
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Re: Accumulator sphere replacement

Originally Posted by ro80rob
I've had a look underneath (and looked in the manual). It seems that it is necessary to 'remove' the forwardmost (front I guess) accumulator unit to even stand a chance of unscrewing the sphere from the rear accumulator.
Hello Rob,
No, it's not necessary.
You put off the first sphère and after the second one, with a facom tool for oil filters.
If the previous work has been good done, it's very easy to change the sphères.

A good done is to tighten the new sphères only with his hands.

A good idea is to put down the rear of the car by occur on the hight régulator with a screwdriver, before shuting off the pressure in the oil circuit, on the 2 régulators.

Best regards

Would you, please, excuse my bad English, I'm just french. Nobody's perfect ....
Bentley turbo R LWB 1997 & Rolls-Royce Silver Spirit 1987
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post #6 of 25 (permalink) Old 07-20-2008, 04:02 PM
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I just replaced spheres on my 1980 Silver Shadow II,
Every time you must replace spheres, you MUST also remove pressure valves (adiacent to spheres) and rebuild them, there's an appropriate rebuilding kit offered by Rolls Royce dealers.
This is important because the new highly pressurized spheres risk to explose, the old dried seals on pressure valves with consequent oil leaking.
When I did it on my 73 Shadow, an other fault occourred:
the rear height control valves was corroded by old (never changed) brake fluid, both them exploded on freeway and had to replace the group.
Also check rubber hoses and eventual oil leakings from rear shock absorbers.
ITS ANYWAY INDISPENSABLE ask to an OFFICIAL Rolls Royce-Bentley mechanic to replace spheres because must be purged the entire brake fluid, replaced with new one (Castrol RR 363 only on Shadows, Corniches, Camargues and Ts and MINERAL OIL on later models) and test each circuit pressure to obtain the desired brakes power and height control fonction.
RED WARNING INDICATORS ON DASHBOARD must be switch off when engine running!!!! BUT often not so good mechanics removed bulbs on dashboards to resolve the fault! So check also warning lamps functionality!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

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post #7 of 25 (permalink) Old 08-18-2008, 04:18 AM
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To answer one of your first questions - the accumulator spheres on green-juice cars are identical to those used on Citroen CX, BX, GS and late DS (and possibly some of the newer ones but I don't know about those). They are available in UK from GSF for about 20UKP - no exchange.

Similarly HSMO=LHM.

The rear suspension spheres are not equivalent to any Citroen sphere, as far as I know, but I would love to know different.

Hint: as someone has said, tighten them only hand tight. Don't spin them down to a stop because the impact of stopping the sphere will lock it on too tight. If it leaks under pressure the O-ring is not seated properly.

Hint: if you can't get it off any other way use a chisel on the outer circumference. Since you are going to throw the old one away, who cares. Citroen specialists (I don't necessarily mean Citroen agents) sell VERY robust tools for removal - the message about fitting them hand tight has still not reached everyone on the garage world.
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post #8 of 25 (permalink) Old 09-30-2008, 07:01 PM Thread Starter
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Hello Alan

You are correct in that the sphere is mechanically a citroen sphere.


The only Citroen sphere that comes close to being correct is the Citroen CX front suspension sphere. This has the same 75 Bar pressure as the RR unit.
But...., it is not an accumulator sphere, so it also has a valve and a restrictor hole (I did my homework on this little lot before I bought replacements). This provides the sphere with the 'shock absorber' effect. The valve opens to let the fluid in as the suspension piston pushes fluid up into the sphere (as you go over the 'bump'). The fluid can only escape through this 1.5mm hole as the spring re-bounds after you have traverseed the 'bump'. This slowed down flow stops the oscillation that would occur otherwise.
Use of this CX sphere on the RR accumulator system is debateable. Do you consider that the sphere would need to pass fluid out to the brakes at a rate quicker than can be supplied by the 1.5mm hole?. That is the question, and not having designed the system, its not possible to be sure.
Personally, I would guess that it would probably be OK, but there is always that element of doubt, so the smart move is to buy the right one and accept the price doubling over and above GSF's prices.
The rear spheres are only 15 Bar pressure and definitely a RR special pressure, though mechanically its the same item.
As for the fluid, I use Citroen LHM. Its available much more readily, though I do decant it into the original Castrol bottle, as that fits in the holder in the boot.
I take on board the 'not overtightening' of the spheres on re-fitting. I bought a tool off Ebay to undo the stubborn ones. As I said earlier, my accumulator spheres are mounted awkwardly, so I think we will have to demount the lower accumulator to get the upper sphere off. We reckon we can get sufficient flex on the pipes on the lower accumulator unit to get enough room to do the upper.
I won't be re-building the whole accumulator though. The car has only done 55k miles. I didn't see any special tips on the Australian site, which is an excellent resource for the DIY mechanic.

Cheers... Rob.

Red to Red, Black to Black, Blew to bits.
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post #9 of 25 (permalink) Old 10-05-2008, 05:14 AM
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Rob, the Citroen manual says the accumulator sphere is nominally 62.5 bar and my Spirit manual says "60 to 64 bar". It may be higher for later cars - I don't have a Turbo R manual - but the difference is trivial anyway because the working pressure is determined by the regulator blow-off setting. If a lower pressure sphere is used a slightly larger volume of oil at slightly faster pressure drop-off would be available in emergency "no-pump" situations, which have a huge margin of safety.

If you want to use a suspension sphere, drill out the hole. It doesn't have to be huge because the rate of flow is very small - think of the cross-section of the pipes. Take precautions to stop filings getting into the fluid and don't drill through the diaphragm plate. The restrictor is only a couple of mms deep. I use this technique to tune the suspension characteristics of my classic Citroens, and so do other people.

Regards from Alan D.
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post #10 of 25 (permalink) Old 12-21-2008, 07:54 PM
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Replacement Spheres

Everyone tries to find a cheaper way to go. In the US, we don't have all the availability as you do in Europe. With over 30 years experience with these cars, my advice is to not substitute much of anything.

Removal of a tight sphere can be accomplished with a chain wrench. This is a very cheap tool available almost anywhere. I have two of them. One has a long handle, the other uses a 1/2" ratchet wrench. Works well in those tight TurboR spots.

Gas Springs, the rear suspension spheres are only calibrated to the cars, do not substitute anything unless you want to ruin the ride. They are not the damper, the shock tube is. Also, replace the bypass tube on the lower end of the shock, otherwise you're going to have leaks eventually.

If you want to save money, get your green fluid from Nissan. It's actually a better product, 1/4 the price, and larger quantity. The Infinity A cars used this fluid and it's fabulous.

You shouldn't have to rebuild the valve assembly. But you should inspect the pumps, as the o-rings are notorious for leakage.

Good luck.
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