Terrifying! And depressing... Log Out | Topics | Search
Moderators | Register | Edit Profile

Australian RR Forums » Silver Shadow Series » Terrifying! And depressing... « Previous Next »

Author Message
Top of pagePrevious messageNext messageBottom of page Link to this message

Chris Miller
Prolific User
Username: cjm51213

Post Number: 135
Registered: 5-2013
Posted on Tuesday, 15 July, 2014 - 01:10 pm:   Edit PostDelete PostView Post/Check IP

Hi Folks,

I have just returned from a terrifying trip. I drove to a supplier about five miles away and just as I pulled into the parking lot, one of the accumulators posted a "zero pressure" warning! And it was real...

I said to myself, "Self, this is really odd. I just rebuilt those accumulators. And bench-tested them! I have complete confidence in them."

So, I pump tested them. The other one was accumulating about twenty strokes of pressure, when this morning it was over fifty. So, one has gone from over fifty strokes to zero and the other from over fifty strokes to about twenty!

Do I have two different and simultaneous failures? If it were just the one going to zero, I could conclude that the intake screen to the pump might be clogged. That would explain zero pressure. However, how do I explain the other one? If the second screen was clogged so flow was reduced, then it would simply take longer to develop full pressure, but I'd still be getting full pressure, and I'm not. And I have new fluid and freshly cleaned screens, so clogged screens are really unlikely.

What gives? Assuming my carefully rebuilt accumulators did not both simultaneously -- and suddenly -- leak nitrogen in different amounts, or the accumulator control valves did not enter into a conspiracy, and that the accumulators are, in fact, still intact, then I fear I have a failure to develop pressure at the pump. However, the same symptoms would be produced if the ACVs suddenly started to misbehave and switch to "bypass" at the wrong pressure. So, pump or AVC? How can I tell?

Suppose the pumps are working, then I will see fluid levels rise as I pump the brakes and then lower as I run the engine. Failure to see such changes means that fluid is not being stored in the accumulator, which can be either the pump is not developing pressure or the ACV is bypassing at the wrong pressure. Can I tell which without removing the accumulators?

Since I have no reason to suspect the accumulators or the ACVs, I suspect the pump... What would cause one pump lose pressure partially and the other to lose pressure completely? Simultaneously?

So, you can imagine the drive home... Yes, I had brakes from one accumulator, the front one, but it was obviously impaired and whatever failure I was seeing could appear in the working system at any moment! And I had not yet tested to see if the master cylinder had any braking credibility whatsoever. I crept home along the shoulder in first gear at 15 MPH and really pissed-off a lot of Californians.

This is probably a pretty good time to test the breaking power of the master cylinder...

Any thoughts?

Chris.
Top of pagePrevious messageNext messageBottom of page Link to this message

Paul Yorke
Grand Master
Username: paul_yorke

Post Number: 1225
Registered: 6-2006
Posted on Tuesday, 15 July, 2014 - 05:08 pm:   Edit PostDelete PostView Post/Check IP

Yes . . . but I doubt you will like it.

"but it was obviously impaired and whatever failure I was seeing could appear in the working system at any moment! And I had not yet tested to see if the master cylinder had any braking credibility whatsoever."

Get a bloody AAA membership!

If you want to risk your own life testing brakes in a deserted parking lot fair enough.

But deliberately driving a car with undiagnosed failed brakes on a public road just because it is more convenient for you is disgusting.

Do you really think that two and a half tons of metal will not damage anything it hits because it is only doing 15MPH?

Put the car in park and your brain in gear!
Top of pagePrevious messageNext messageBottom of page Link to this message

Chris Miller
Prolific User
Username: cjm51213

Post Number: 136
Registered: 5-2013
Posted on Tuesday, 15 July, 2014 - 10:53 pm:   Edit PostDelete PostView Post/Check IP

O.K., Paul, feel better?

The question I am posing is, given a running engine and a red "zero pressure" warning, we know the accumulator had no fluid. I can think of two ways that might happen. The pump might not be developing any pressure or the ACV might be bypassing at the wrong charging pressure, zero in this case.

Can you devise a test that will determine if the pump has failed or the ACV has failed?

I could remove the accumulator and re-bench test. I could remove the lid of the reservoir and test to see if fluid is circulating. I could open up the pump and visually inspect for damage. Is there some way to make this determination based on observation without all the intrusion?

Thanks for the help,

Chris.
Top of pagePrevious messageNext messageBottom of page Link to this message

Richard Treacy
Grand Master
Username: richard_treacy

Post Number: 3032
Registered: 4-2003
Posted on Tuesday, 15 July, 2014 - 10:58 pm:   Edit PostDelete PostView Post/Check IP

Wow, Paul.

quote:

Put the car in park and your brain in gear!


That's a bit extreme. And rude surely ?

No. Not really. Not at all. Just common sense, so thank you.

DIY accumulators, RR363 home brew and substandard brake pads on below-spec disc rotor thicknesses with grooves are a hazard to the general public. I just wonder at those who take shortcuts on safety items when the proper parts are available at very reasonable prices.

Pads. Sure you can buy cheapies sold for Holden HD-HK cars (those are ancient Australian cars by General Motors like Vauxhauls, and probably Australian-made and English-made made Ford Cortina stuff fits too), but they use the budget material.. They provide poorer brake fade and excessive (often punishing) disc rotor wear results. If you spend a few dollars more and buy Ferodo equivalents in the premium version they are correct, delivering less brake fade and longer component lives. Surprise, surprise. Crewe sells the same Ferodo premium pads in a Crewe box, but believe it or not, the Crewe price is lower.

Likewise, exchange accumulators are not at all expensive from a proper outfit (Paul, do you offer them ?) and disc rotors are strictly routine replacements as are brake hoses and brake caliper overhaul kits.

RT.
Top of pagePrevious messageNext messageBottom of page Link to this message

Richard Treacy
Grand Master
Username: richard_treacy

Post Number: 3033
Registered: 4-2003
Posted on Tuesday, 15 July, 2014 - 11:26 pm:   Edit PostDelete PostView Post/Check IP

All this stuff is not expensive, especially compared to the price of a tank of fuel. LPG, pwtrol or diesel alike.
Top of pagePrevious messageNext messageBottom of page Link to this message

Bob uk
Unregistered guest
Posted From: 94.197.122.89
Posted on Wednesday, 16 July, 2014 - 05:57 am:   Edit PostDelete PostView Post/Check IP

All brake parts that I buy come via a large well known UK motor factor who doesn't sell substandard parts because they also supply police and other gov agencies

Brake friction material comes in different grades

The grade is chosen by how a car is likely to be driven

The makers don't know so they pick a middle of the road grade

A race shop near me has 2 choices road or green race

Thin pads will transmit more heat to the dot I change at 1/2 thickness

To check ventilated disks I like to remove so I can see the backs properly

A certain level of scoring is ok
and will not affect the brakes

Although a bit more bedding in will be needed when New pads are fitted

Accumulators have to be right

The pumps output approx 1/2 cc per
Stroke which is at 1/2 engine speed

If the accumulators are down there is no reserve and the brakes will fad because the pump can't keep up unless the engine is revved

A crash is most likely

When I used to test police cars I would give the brakes serious "abuse" we wasn't happy until we could light a fag from the heat

70 mph on and off the brakes abs cutting in and out

When I do my 6 week brake test I am not so brutal ( it's my car)

If it doesn't come up to snuff it gets fixed until it does

They rest of the time I read the road and hardly use the brakes

I was unhappy about your warning lights.

Mine come on at about 1500 psi meaning I still have brakes to stop with

I would like permanent 3000 psi gauges fitted

Run engine at 1000 rpm the pump should output 250 cc a minute via the valve body bleeder

I replaced my accumulators in 1996
£140 for 2

The front has 90 pumps to lights on
The rear 70

Front holds pressure for 12 hours

Rear because it is trying to level the car 1 hour my rear springs are a bit saggy if the springs were better then Maybe far longer

My hydraulics are good because I religiously follow the manual and have good working practices

I do nothing in a hurry

I was also good at working for the government

(Message approved by david_gore)
Top of pagePrevious messageNext messageBottom of page Link to this message

Bob uk
Unregistered guest
Posted From: 94.197.122.73
Posted on Friday, 18 July, 2014 - 08:56 am:   Edit PostDelete PostView Post/Check IP

Chris

Now that you have been told off

I will explain

First refer to.chapter G in manual

Find fault finding flow chart

Follow the procedures

To test pressure relief valve

Disconnect return line to tank plug tank side to stop dot draining out

Start engine if dot flows from the return with no pressure on the gauge then the valve is not seating and most likely dirt

If gauge shows pressure and the pump give 250cc at 1000rpm then pumps are good

Most likely accumulatore have failed

Don't worry nobody died

I have made errors and ended doing a job twice

I have never repaired any accumulators only watched

The two halves of sphere must not turn against each other when tightening the lock ring

My accs were charged many weeks before I picked them up the guy checked them while I waited to make sure they were 1000psi took my old ones in exchange

In the manual it explains that the prudent RR garage keeps charged accs in stock and retest before using

This will show up any leaks

Dirt is the enemy of hydraulics in general

(Message approved by david_gore)
Top of pagePrevious messageNext messageBottom of page Link to this message

Chris Miller
Prolific User
Username: cjm51213

Post Number: 142
Registered: 5-2013
Posted on Tuesday, 22 July, 2014 - 02:37 am:   Edit PostDelete PostView Post/Check IP

Hi Bob (UK),

You're right. I lost Nitrogen. I excluded that because I just rebuilt these accumulators and the reason I did that was because I was losing nitrogen, so that problem should no longer be evident, right? Well, "once more unto the breech"; I'm just going to have to keep doing this until I get it right.

Once I realized that with the exception of failed pumps, every other failure will require me to remove the accumulators anyway, I determined that I could identify a pump failure pretty easily. I evacuated the accumulators with the "pedal test". I attached a hose to the front calipers. I opened the bleed valve and I noticed a small amount of fluid emerge. I started the engine and depressed the brake pedal. I saw a steady stream of fluid. So, from this I conclude that the pumps are functionally working, but the question of pressure is deferred until I rebuild (again) my accumulators, and bench test them so I know the ACV is working, and I know the pressure necessary to engage the by-pass. I will complete the pump test when I put the accumulators back and confirm that the pumps are producing pressure necessary to engage the ACV by-pass.

Thanks for the discussion and the help clarifying the problem definition,

Chris.
Top of pagePrevious messageNext messageBottom of page Link to this message

Brian Vogel
Grand Master
Username: guyslp

Post Number: 911
Registered: 6-2009
Posted on Tuesday, 22 July, 2014 - 03:05 am:   Edit PostDelete PostView Post/Check IP

Chris,

Have you found a viable technique for removing just the accumulator sphere that doesn't require the ACV to come out along with it?

Your car is, I believe, an SY1 series so I think this is an easier task, anyway, but I've been trying to figure out if there's a way to get an accumulator off of the ACV without damaging either.

Brian
Top of pagePrevious messageNext messageBottom of page Link to this message

Chris Miller
Prolific User
Username: cjm51213

Post Number: 143
Registered: 5-2013
Posted on Tuesday, 22 July, 2014 - 03:15 am:   Edit PostDelete PostView Post/Check IP

Hi Brian,

The answer is "Yes.", and you're right, it is a whole pile easier! However there is a catch that will cause howls...

When I rebuilt my accumulators, I learned, because I had bench testing ability where I could test and find leaks, that the sphere can be threaded into the ACV finger tight! Believe it or not, no tools are required to re-attach it, which means subsequent removal is also a no tools required operation. Leaks would be obvious, since you'd see brake fluid drips, but it will not leak. So, next time you remove your accumulators, restore the sphere to the ACV without any tools, which will allow you to remove it without any tools.

Let the howls begin... (-:

Chris.
Top of pagePrevious messageNext messageBottom of page Link to this message

Brian Vogel
Grand Master
Username: guyslp

Post Number: 914
Registered: 6-2009
Posted on Tuesday, 22 July, 2014 - 04:05 am:   Edit PostDelete PostView Post/Check IP

Chris,

Well, I'll howl slightly because I'd be concerned that they could work loose secondary to vibration at just "finger tight" though "grab ring with both hands and turn" tight would probably be sufficient. The O-ring itself acts as a bit of a locking mechanism.

After all, 55-60 ft-lb is not a massively tight torque figure.

Brian, who already has his accumulators attached to their respective ACVs at the Chapter P specified torque figure, noted above
Top of pagePrevious messageNext messageBottom of page Link to this message

Chris Miller
Prolific User
Username: cjm51213

Post Number: 148
Registered: 5-2013
Posted on Tuesday, 22 July, 2014 - 04:33 am:   Edit PostDelete PostView Post/Check IP

Hi Brian,

Yeah... I used one hand. I have only 50 miles of experience in the "might work loose" department, but the '72 has an integrated bolt in the end caps on the check valve, that provide support from a brace, and I think that part will keep anything from working loose. I know that this was added after '66, and I suspect that it was never deleted, because it simply make sense.

Since we are talking about "pro-active" steps with the accumulators off, I can tell you that I caused myself huge headaches requiring that I re-manufacturer the 3/8" high pressure line from the forward pump to the forward accumulator. And I damn near did it a second time, knowing that it could happen!

JIC Fitting

The 3/8" high pressure line connects to the ACV at a JIC flare fitting. This fitting is threaded into the ACV. So, if you have a clear picture in your mind, there are TWO sets of threads there -- one for the flare cap on the JIC flare fitting and one for the fitting to thread into the ACV body, and guess which one loosens first? If you guessed the cap, you'd be wrong and you'd probably do what I did -- twist up the 3/8" line because the cap kept the line tight to the flare fitting, as the cap turned the fitting with the 3/8" tube...

Yes. There is a hex face so you can use two wrenches to isolate these, but you have to realize what is happening, before it is too late, because you don't expect it, and it is cramped space for working with two hands and two wrenches, but it obviously can be done.

The proactive step here is to use a thread lock on the JIC fitting/ACV threads, so the cap will loosen before the fitting, and there is probably no reason to ever want that fitting to come out, unless you have the ACV on the bench and you can heat it to release the thread lock. I spent a lot of time thinking, "Geeze, if I could do this over, I would ..."

For your consideration,

Chris.
Top of pagePrevious messageNext messageBottom of page Link to this message

Bob uk
Unregistered guest
Posted From: 94.197.122.86
Posted on Tuesday, 22 July, 2014 - 05:46 am:   Edit PostDelete PostView Post/Check IP

Someone on this site commented that rear rams are often overtightened as though it was trying to contain a nuclear explosion.
I think that fully seated and a nip is enough.


My car the accs were seated and then a nip with a oil filter strap
They don't leak and were fitted 18 years ago.

In general if a hydraulic fitting is lightly nipped it should not leak. If it does then the seats are dirty, damaged, or whatever.

Brake line tube nut fittings if left loose will drip but under pressure the fitting will try to pop out and seal itself.

Just a nip is all that is needed. Overtightened fittings just ruins fittings.

Typically the plain bit next to the flare buckles out and when unscrewed damages the thread of the bit it was screwed into.

The 3/16 pipe fittings are 3/8 unf except the front calipers 10mm fine at the caliper end.

(Message approved by david_gore)
Top of pagePrevious messageNext messageBottom of page Link to this message

Bob uk
Unregistered guest
Posted From: 94.197.122.75
Posted on Tuesday, 22 July, 2014 - 07:26 am:   Edit PostDelete PostView Post/Check IP

And
If the brake pedal is depressed with the lights on and the engine started because pressure holds the valve shut the pedal will kick back.

Is another way of showing that at least one pump is working

(Message approved by david_gore)
Top of pagePrevious messageNext messageBottom of page Link to this message

Bob uk
Unregistered guest
Posted From: 94.197.122.85
Posted on Tuesday, 22 July, 2014 - 06:42 am:   Edit PostDelete PostView Post/Check IP

Before removing the valve accumulator ass. loosen the accumulator, when refitting hand tighten fit to car then nip

(Message approved by david_gore)
Top of pagePrevious messageNext messageBottom of page Link to this message

David Gore
Moderator
Username: david_gore

Post Number: 1402
Registered: 4-2003
Posted on Tuesday, 22 July, 2014 - 11:33 am:   Edit PostDelete PostView Post/Check IP

Gentlemen,

I am becoming concerned with the procedures and related matters being discussed in this thread as they involve the high pressure hydraulic system and also the driving of vehicles with suspect brake systems on public roads.

I [and certainly the RROCA] would be extremely unhappy if one of our members let alone innocent members of the public were injured or worse as a consequence of inappropriate service techniques, unsafe workshop testing and/or dangerous road testing of vehicles. The fact that serious problems with "repaired/overhauled" components have been encountered after they are reinstalled in the vehicle suggest the recommended procedures for overhauling the parts and/or standard hydraulic workshop practice are either being ignored or overlooked. Hydraulic service technicians undergo extensive and rigorous training based on long standing experience and practice before they work unsupervised because of the inherent risks and adverse consequences of service failures due to unsuitable/untested repair/overhaul techniques. Some of the questions being asked suggest the individuals concerned may have minimal understanding of the basic principles of hydraulics and, in particular, how hydraulic components function and how they fail.

Owners considering the option of doing their own hydraulic maintenance should only do so if they have the training and experience to do so or a suitably experienced person is available to supervise and comment during the overhaul process. Above all, always respect and consider the information provided by professionals who have the knowledge and experience to do the job properly and safely; they know what can go wrong and how to test that the repair has been successful before the component is reinstalled. Ignore their comments and the outcome may not be what you expected.

There is a lot of experience and knowledge held by members of this forum who are prepared to share this with others who recognise their limitations and lack of knowledge by asking for information before starting work instead of doing things "their way", encountering problems and then seeking help for largely avoidable and sometimes expensive problems of their own making.

Above all, readers of this forum do so subject to the condition that any information is of a general nature only and does not constitute professional advice or recommendations; it is the reader's obligation and responsibility to seek professional assistance from a suitably qualified person before proceeding with any repair/maintenance procedure where they do not have the requisite knowledge and/or experience to undertake the work required safely, competently and compliant with relevant standards and specifications.
Top of pagePrevious messageNext messageBottom of page Link to this message

Paul Yorke
Grand Master
Username: paul_yorke

Post Number: 1230
Registered: 6-2006
Posted on Wednesday, 23 July, 2014 - 02:04 am:   Edit PostDelete PostView Post/Check IP

Hand tighten the accumulators. Don't be so incredibly stupid. So it's easy to get off again. Hell why not just leave everything loose????

Get the job done properly. Use properly overhauled parts. Fit them correctly and you won't need to play around with them again for many many years. You won't need to worry about taking them off for many many years.

If a jobs worth doing - do it right.
If in doubt - renew throughout.

Two maxims from the Rolls-Royce workshop floor.

You are asking for catastrophic failures by pratting about with these systems.

To be honest- it is not, imho, a question of legality or whether the insurance company pays out or the owner has to sell everything to pay some liability because of an accident.

The shocking gists of these posts are you don't give a damn about other human beings. If anybody is driving a car with faulty brakes and unknown faults or faults they should be made to jump out in front of it. Not a car you have just bought with undeclared or hidden faults, but one that you have personally made dangerous! The fact is that when somebody is 'playing' at fixing cars but does not give a flying **** about others they should be getting their selves checked out . . . not their cars.

Do you honestly think a family who has just lost a couple of kids because some prat feels like trying out a few experiments on two and a half ton lump of metal cares whether it is legal or not. Whether an insurance company is paying for their kids funeral or not.

PUT YOUR BLOODY BRAIN IN GEAR AND REPAIR THINGS PROPERLY OR GET SOMEBODY WHO CAN DO THE JOB PROPERLY!!

There is being cheap - not paying for repairs you CAN'T do yourself.

There is utter tightness. Not buying the correct parts to do a safe repair.

And there is plain selfish unbelievable stupidity. Not been able to do a repair and then imagining you can by making up some kind of sh1t with crap that you just have hanging around the sweepings on the floor. Have a rummage through and you will probably find thousands of lost brain cells in that sawdust as well!

Some people do not deserve to be allowed to have a Rolls-Royce let alone allowed out on the public roads.

As a professional R-R & B engineer I implore people to ignore this thread and the rantings of somebody who has no idea about how stupid the things they are suggesting are.
Top of pagePrevious messageNext messageBottom of page Link to this message

Chris Miller
Prolific User
Username: cjm51213

Post Number: 154
Registered: 5-2013
Posted on Wednesday, 23 July, 2014 - 02:15 am:   Edit PostDelete PostView Post/Check IP

Hi Paul,

> Hand tighten the accumulators. Don't be so incredibly stupid.
> So it's easy to get off again. Hell why not just leave everything loose????

Well, as loose as necessary. Hand tight is all that is necessary. If the sphere is not sufficiently tight, then it will be quite immediately obvious; you will have a brake fluid leak. Mine never leaked brake fluid; mine leaked nitrogen. So, experience and evidence bears out the conclusion.

For your consideration,

Chris.
Top of pagePrevious messageNext messageBottom of page Link to this message

Bob uk
Unregistered guest
Posted From: 94.197.122.89
Posted on Wednesday, 23 July, 2014 - 06:46 am:   Edit PostDelete PostView Post/Check IP

Chris.
You are wrong to say finger tight is ok to make dismantling easy.

Oil filters are spun on hand tight.

By a nip I mean with a strap wrench or similar and a firm pull. Not legs braced against the hub with neck veins bulging that's for getting tight ones off.

RR don't make cars that need a brake overhaul every month. If the job is done properly then it will last.
Mine has lasted 18 years from a good check over part overhaul, with 6 week checks (2 hours no rushing) as recommended by the AA, RAC and others.
The reason I said that to loosen and tighten the accumulators while on the car is that a vice could damage the valve body. Whereas bolted to car has 2.3 tons holding the valve body steady.

The adaptor doesn't need chemical locking. Chemical thread locking stuff is designed to be undone with normal hand tools. It doesn't lock just stiffens the action.

I don't mess with accumulations because of the safety and I have had no training. I know how they work which is enough to diagnose. Plus I have someone to blame should it all go badly wrong.
I have as every body has a duty of care to property and people which in the UK is law.
Every once in a while someone is nicked by the health and safety executive and get prison or seriously fined. £10K is not unknown
Because I have engineering knowledge I would have no defence.
You have had 2 near misses 3rd time lucky
The 3rd time might land you in the do do.

Bite the bullet and get the accs pro overhauled.
I am happy with well engineered sensible bodges but not high pressure anything.

(Message approved by david_gore)
Top of pagePrevious messageNext messageBottom of page Link to this message

Chris Miller
Prolific User
Username: cjm51213

Post Number: 155
Registered: 5-2013
Posted on Wednesday, 23 July, 2014 - 07:41 am:   Edit PostDelete PostView Post/Check IP

Hi Bob,

The requirement is that there be no leak between the ACV and the sphere. It requires no tools to accomplish this.

For your consideration,

Chris.
Top of pagePrevious messageNext messageBottom of page Link to this message

Bob uk
Unregistered guest
Posted From: 94.197.122.82
Posted on Wednesday, 23 July, 2014 - 08:53 am:   Edit PostDelete PostView Post/Check IP

Chris
The manual is for the guidance of the wise and for the obedience of fools.

Imagine that the accumulator is fitted to a aeroplane.----

The reason the accumulator has to be tight is that there is a real danger that the o ring will blow out.

I have seem oil pressure relief valves jam and blow the seal out of a spin on oil filter. Ford V4 and V6 Essex engines used to do this.

Your coming into land and the plane yaws left and the pilot gives a little bit of right rudder and the accumulator seal blows, the plane will cart wheel down runway in a fireball.
I am trying not to be rude.}}

(Message approved by david_gore)
Top of pagePrevious messageNext messageBottom of page Link to this message

Chris Miller
Prolific User
Username: cjm51213

Post Number: 156
Registered: 5-2013
Posted on Wednesday, 23 July, 2014 - 02:37 pm:   Edit PostDelete PostView Post/Check IP

Hi Bob (UK),

As you spin the sphere on to the ACV, it goes through three distinct stages. The first stage is the first dozen or so spins. The second stage is when the o-ring in the sphere makes contact with the mating surface on the AVC and the spinning is slightly less free. The third is when the two steel mating surfaces touch, and it quickly becomes much harder to turn at that point.

You can reach the third stage without any tools, and there is no chance for the o-ring to blow out, since it is completely contained. Any torque beyond this is unnecessary since you have done what is required -- keep the brake fluid in the brake system.

I don't know if Rolls Royce designed this behavior, but it is so beautiful, that I'd like to believe they did.

For your consideration,

Chris.
Top of pagePrevious messageNext messageBottom of page Link to this message

David Gore
Moderator
Username: david_gore

Post Number: 1409
Registered: 4-2003
Posted on Wednesday, 23 July, 2014 - 03:47 pm:   Edit PostDelete PostView Post/Check IP

Chris,

Have you considered the need for the tightening procedure to generate residual tensile stresses in the accumulator bodies to compensate for thermal expansion when the accumulators warm up when the car is being driven?

A closed gap at room temperature can become an open gap when hot if there is no residual tensile stress to keep the bodies locked together. This is why tightening torque figures are often specified for threaded components and always for critical components. I note TSD 2476 Section P specifies a torque of 55/60 ft.lbs for the accumulator sphere to valve body and a torque of 265/275 ft.lbs for the accumulator bodies. I am in no doubt the Citroen and Rolls-Royce engineers who designed and tested the Shadow hydraulic system knew what they were doing and the torque specifications in the workshop manual were derived from their knowledge and experience. I am certain a Rolls-Royce professional such as our member Paul Yorke would be well aware of any subsequent changes to specified procedures through Service Bulletins and his comments in this thread indicate this has not been the case.

I respectfully suggest you and I are not qualified to suggest let alone recommend any changes to or deviations from the recommended procedures. In fact, I suspect your loss of gas charge may have been due to separation of the housings when hot due to thermal expansion and operating gas pressure; the use of insufficient tightening torque allowed the gas charge to escape causing your loss of braking capacity.

"You can reach the third stage without any tools, and there is no chance for the o-ring to blow out, since it is completely contained. Any torque beyond this is unnecessary since you have done what is required -- keep the brake fluid in the brake system.

I don't know if Rolls Royce designed this behavior, but it is so beautiful, that I'd like to believe they did."


I certainly do not think this statement is correct - if they did design it in the way you suggest, the workshop manual would specify your procedure rather than the alternative specified in the manual or there would have been a subsequent Service Bulletin advising the revised procedure.
Top of pagePrevious messageNext messageBottom of page Link to this message

Richard Treacy
Grand Master
Username: richard_treacy

Post Number: 3040
Registered: 4-2003
Posted on Wednesday, 23 July, 2014 - 05:41 pm:   Edit PostDelete PostView Post/Check IP

Further to Davidís comments, Chris you are relying on the o-ring as a friction device to stop the sphere from rotating. You may say that a spin-on oil filter does the same, but that would be misleading. The filter has a flat high-friction seal which takes all the torque with no metal-to-metal end stop and is designed for the purpose. The sphere by contrast has an o-ring only partially compressed in its cavity and is not made of a friction material Ė quite the reverse. The sphere definitely needs to be nipped up to a torque as David explains.

This being a public Forum, observers out there must think that we are Cowboys from the Wild West promoting dodgy practices and second-rate components. Canít we lift the game ?

RT..
Top of pagePrevious messageNext messageBottom of page Link to this message

Chris Miller
Prolific User
Username: cjm51213

Post Number: 157
Registered: 5-2013
Posted on Wednesday, 23 July, 2014 - 11:43 pm:   Edit PostDelete PostView Post/Check IP

Hi David,

> Have you considered the need for the tightening procedure
> to generate residual tensile stresses in the accumulator
> bodies to compensate for thermal expansion when the
> accumulators warm up when the car is being driven?

No, I haven't because, as I've said, the goal is to keep the brake fluid in the brake system and that goal is accomplished. If this were a necessary consideration, then I would see operational brake fluid leaks, and I don't.

> In fact, I suspect your loss of gas charge may have
> been due to separation of the housings when hot due
> to thermal expansion and operating gas pressure;
> the use of insufficient tightening torque allowed
> the gas charge to escape causing your loss of braking capacity.

This is possible and a valid engineering concern and consideration, but I'm pretty sure that the nitrogen escaped through the check valve. That experiment yielded some lessons and some design improvements ...

How do you go from "spin the sphere on finger-tight", and I agree "finger-tight" is not a well defined term, although I have explained what I mean earlier, to "failure to adequately torque the sphere composition joint"? That is a rhetorical question; please don't answer it... These things are unrelated and nowhere do I advocate gentle force when it comes to composing the containment body of the sphere.

If you're really interested in discussing the engineering, than so am I, but so far I have seen far more heat than light, and it is wearisome.

Chris.
Top of pagePrevious messageNext messageBottom of page Link to this message

Chris Miller
Prolific User
Username: cjm51213

Post Number: 158
Registered: 5-2013
Posted on Wednesday, 23 July, 2014 - 11:54 pm:   Edit PostDelete PostView Post/Check IP

Hi Richard,

> you are relying on the o-ring as a friction device
> to stop the sphere from rotating.

No, I'm not. I'm relying on the friction between the steel mating surfaces of the ACV and the shpere, with additional stabilization from the threaded post on the check valve cap. I mention the o-ring because it is a very important part of the "feel" as you reassemble the accumulator from the sphere and the ACV.

> You may say that a spin-on oil filter does the same, but that would be misleading.

No, not misleading at all. The pressure ranges are an order of magnitude different, true, but the containment failure (brake fluid leak, oil leak) are immediately obvious and quite easily rectified, although a bit of foresight avoids the need to "rectify" anything.

For your consideration,

Chris.
Top of pagePrevious messageNext messageBottom of page Link to this message

Mark Aldridge
Prolific User
Username: mark_aldridge

Post Number: 139
Registered: 10-2008
Posted on Thursday, 24 July, 2014 - 12:45 am:   Edit PostDelete PostView Post/Check IP

The situation here in the UK may be different, but paying £120 for a guaranteed recon sphere seems cheap and effortless.
Mark
Top of pagePrevious messageNext messageBottom of page Link to this message

Jeff Young
Prolific User
Username: jeyjey

Post Number: 191
Registered: 10-2010
Posted on Thursday, 24 July, 2014 - 01:00 am:   Edit PostDelete PostView Post/Check IP

Just wanted to say that I have found this discussion useful and interesting.

Yes, perhaps a little too much "heat" at times, but at least I know when the poster feels strongly.

At the end of the day, sometimes I feel like paying to have something done, and sometimes I feel like doing it myself. This usually has more to do with how much enjoyment vs. hassle I think the job might be than cost.

When I do choose to roll up the sleeves, these discussions are a gold-mine of things to consider.

Cheers,
Jeff.
Top of pagePrevious messageNext messageBottom of page Link to this message

Richard Treacy
Grand Master
Username: richard_treacy

Post Number: 3041
Registered: 4-2003
Posted on Thursday, 24 July, 2014 - 01:05 am:   Edit PostDelete PostView Post/Check IP


quote:

additional stabilization (sic vs stabilisation) from the threaded post on the check valve cap.




Brave indeed.

quote:

The situation here in the UK may be different, but paying £120 for a guaranteed recon sphere seems cheap and effortless.




Agreed.

Translated into American:
The zituation here in the UK may be different, but paying £120 for a guaranteed recon zphere zeemz cheap and effortlezz.
Top of pagePrevious messageNext messageBottom of page Link to this message

Brian Vogel
Grand Master
Username: guyslp

Post Number: 921
Registered: 6-2009
Posted on Thursday, 24 July, 2014 - 01:38 am:   Edit PostDelete PostView Post/Check IP

Jeff,

I couldn't have said it better myself (and didn't).

The fact is that rebuilding an accumulator and an accumulator control valve really is not rocket science. The accumulator is an utterly simple thing and as long as you've got the pin wrench and strength to get them apart and put back together you're fine.

For myself, I don't think that re-creating the accumulator charge port sealing mechanism that I've seen in the Flying Spares kit is sacrilege nor inherently unsafe. Careful monitoring afterward is required.

Brian
Top of pagePrevious messageNext messageBottom of page Link to this message

Chris Miller
Prolific User
Username: cjm51213

Post Number: 161
Registered: 5-2013
Posted on Thursday, 24 July, 2014 - 03:06 am:   Edit PostDelete PostView Post/Check IP

Hi Richard,

> Translated into American:
> The zituation here in the UK may be different,
> but paying £120 for a guaranteed recon zphere
> zeemz cheap and effortlezz.

Who knew you had a sense of humor? Ha! (For those of you that don't know me well, that is amusement, not derision.)

Chris.
Top of pagePrevious messageNext messageBottom of page Link to this message

Paul Yorke
Grand Master
Username: paul_yorke

Post Number: 1231
Registered: 6-2006
Posted on Thursday, 24 July, 2014 - 04:22 am:   Edit PostDelete PostView Post/Check IP

Well, as loose as necessary. Hand tight is all that is necessary. If the sphere is not sufficiently tight, then it will be quite immediately obvious; you will have a brake fluid leak. Mine never leaked brake fluid; mine leaked nitrogen. So, experience and evidence bears out the conclusion.

You are the most dangerous type of fool If you truly believe that 50 miles of testing even remotely proves a point like this.

Things loosen themselves. That is a fact that you will never be able to change.

Badly fitted and Loose oil filters do not always leak upon start up . . . with catastrophic engine damage. FACT. Same for hydraulic components.

I know some guy who was convinced he'd overhauled his accumulators safely but once they had warmed up a couple of times completely lost their nitrogen,

I'm waiting for some idiot to come back and say . . . doh if you leave things that are supposed to be tight - loose . . . that's called a f**king mistake.

True . . . . in any language.
Top of pagePrevious messageNext messageBottom of page Link to this message

Chris Miller
Prolific User
Username: cjm51213

Post Number: 162
Registered: 5-2013
Posted on Thursday, 24 July, 2014 - 04:29 am:   Edit PostDelete PostView Post/Check IP

Hi Paul,

> Things loosen themselves. That is a fact
> that you will never be able to change.

Yes, this is true and a really good design takes this into account and mitigates it. Sometime after 1966 Rolls Royce added the threaded post to the check valve cap and a frame-mounted plate for this attachment. The threaded post on the check valve cap prevents the sphere from rotating with respect to the ACV, so it will not loosen.

For your consideration,

Chris.
Top of pagePrevious messageNext messageBottom of page Link to this message

David Gore
Moderator
Username: david_gore

Post Number: 1413
Registered: 4-2003
Posted on Thursday, 24 July, 2014 - 07:43 am:   Edit PostDelete PostView Post/Check IP

I think this is an appropriate time to close this thread.

I caution anyone contemplating alternative maintenance practices to those specified by R-R Motor Cars to either seek professional advice before proceeding or take the safest way out by purchasing reconditioned components from a reputable supplier.