Spheres

Mandrake · Post by **Mandrake** » 24 Jan 2006, 00:57

AndersDK wrote:Simon -

There are no mating faces metal to metal - on any sphere mounts.
That would not work as the seal would then not be allowed to function.
The tightness of the joint relies 100% of the slightly compressed seal between the 2 metal surfaces.

Hi Anders,

I'm puzzled, I wonder if you have looked closely at them

I never said that the mating metal faces provided the pressure seal, I said that the mating metal faces can rust together and cause it to need "cracking" when undoing them. Of course the sealing is provided by the seal

If you look closely you will see that the square section seal is *slightly* thicker than the depth of groove it sits in when uncompressed eg. it stands slightly proud of of the flat metal face around it.

When you screw the sphere on, the metal face on the sphere compresses the seal slightly (by about 0.5mm) and then comes to rest on the outer metal face (shoulder) of the base it is being screwed onto.

Therefore the seal is slightly compressed and clamped in place providing the sealing, but there is also direct metal to metal contact between the outer section of the sphere face and the non-recessed outer part of the base its screwing onto.

It's this metal to metal contact that prevents you from being able crush the seal by overtightening it. If as you said there was no metal to metal contact, someone heavy handed could easily crush the seal flat by overtightening

(which doesn't happen)

The correct compression of the seal is provided by the precise thickness of the seal relative to the recess depth. An overtightened sphere doesn't damage the seal, it just bites even harder on the metal to metal face and makes it more difficult to unscrew.

Regards,
Simon

AndersDK · Post by **AndersDK** » 24 Jan 2006, 01:36

Rubbish -
You can overtighten a sphere if you want. The result would be that the seal will twist and then no longer fulfill its job. This is often done by first timers on replacing the spheres. The seal is simply pressed up/out the location bore and LHM pours out much to the owners panic.

Try screw down a sphere on a suspension cylinder (with a seal) - then unwind it and look for any contact markings on the cylinder - see any ?
I have not.

Do a lab test in your workshop :
In your vice clamp any base that will hold a sphere. Place a dry seal (new or used) then tighten the sphere as hard as you ever can using hand force. Now place your sphere removal tool on the sphere and start slightly un-torque it.
What happens ?

If you look closely you can see/feel that the sphere (and your tool) is moving ever so slightly in the sphere base - because of the soft rubber it is torqued against. The sphere will not release unless you put an amazing torque on your tool - and you can clearly feel its not a metal/metal contact you are cracking - but a metal/rubber contact.

Mandrake · Post by **Mandrake** » 24 Jan 2006, 06:59

AndersDK wrote:Rubbish -
You can overtighten a sphere if you want. The result would be that the seal will twist and then no longer fulfill its job. This is often done by first timers on replacing the spheres. The seal is simply pressed up/out the location bore and LHM pours out much to the owners panic.

It is quite impossible for a correctly fitted seal to be pressed out of the correct location by over tightening - it is fully captive once the sphere is screwed on to the point where it is starting to become tight, and the metal shoulders act as a limit stop to prevent you compressing the seal too far.

It *can* happen if the seal is placed over the neck of the sphere instead of in the groove, (in which case it will get pinched) or if the seal is not lubricated it can be twisted and damaged due to it gripping the sphere instead of allowing the sphere to slide against the seal.

These are the mistakes first timers make that cause a leaking seal. The mistake of overtightening the sphere just makes life difficult for the next person who tries to undo the sphere.

Try screw down a sphere on a suspension cylinder (with a seal) - then unwind it and look for any contact markings on the cylinder - see any ?
I have not.

Why do you expect to see visible markings ?

Why not do the test properly and do something such apply some bearing blue to one face, screw it on, then remove it and you will see clearly the contact areas. Just because you don't see visible gouges doesn't mean there is no contact

Do a lab test in your workshop :
In your vice clamp any base that will hold a sphere. Place a dry seal (new or used) then tighten the sphere as hard as you ever can using hand force. Now place your sphere removal tool on the sphere and start slightly un-torque it.
What happens ?

What happened when I just tried it (on a pressure regulator base) is that I was able to undo it by hand with roughly similar strength to what I tightened it with. The dry seal made little difference to the ability to undo it compared to a lubricated seal or no seal at all.

If you look closely you can see/feel that the sphere (and your tool) is moving ever so slightly in the sphere base - because of the soft rubber it is torqued against. The sphere will not release unless you put an amazing torque on your tool - and you can clearly feel its not a metal/metal contact you are cracking - but a metal/rubber contact.

I simply don't understand where you get this idea from Anders, it is 100% clear to me that there is solid metal to metal contact when a sphere is tightened even with one hand. Look at the profile of the joint. How can it not contact ?

As you screw it on you can start to feel some resistance as the seal begins to compress and then approx 1/4 of a turn after that it suddenly becomes tight as the metal faces bite into each other. Beyond this torque you cannot compress the seal any significant amount further, only increase the bite of the metal faces.

The seal is captive and without the metal shoulder on the outside of the seal the seal could never hold the pressure without blowing out.

There is simply no way that the sphere is torqued soley against the rubber seal with no metal contact. Try inspecting the joint with a magnifying glass as it is tightened.

It seems we will just have to agree to disagree

Regards,
Simon

Homer · Post by **Homer** » 24 Jan 2006, 07:49

mezuk04 wrote: 1. Ride height to minimum (I shall be putting the car onto car ramps at the front).

You won't need ramps to do the spheres and I would keep it on the ground unless you plan to change the accumulator or a height corrector at the same time.

As for changing the filters more often. If you don't mind the expense then it certainly won't do any harm.

andmcit · Post by **andmcit** » 24 Jan 2006, 08:36

AndersDK wrote:
andmcit wrote:That strap wrench on the link looks a tad lightweigt!! Is that band fabric!?

I agree that the usual oil filter chain wrenches don't fare well with stubborn spheres but I do use the following when the proper Citroen band wrench is too chunky to gain access:

http://www.machinemart.co.uk/product.asp?p=040210037

It is akin to a motorcycle chain more than a bicycle!!

Andrew
Andrew -

Steel chain tools are in fact dangerous to use on circular steel members to be unscrewed. Because steel to steel has very low friction. This makes it very prone to slip while you apply your last bit of hand torque. For some reason your hands always stops against something VERY hurting

Its kind of an outdated old fashion tool - because "thats what we always use when its stuck".

Frankly, I don't want to get involved in any for & against conflab.

I'm simply suggesting an alternative that HAS worked for me and not YET let me down - certainly not had slippage that damages anything! [ME OR THE CAR]. This has worked well for me in circumstances where the access to the sphere is limited due to surrounding clutter in the engine bay.

The chain may have less surface area actually gripped than the continuous metal band type BUT it does grip. Both are immeasurably better than a cold chisel and hammer...or welding a lug to pound against on the sphere itself!! Any tool is only as good as how you use it, goes without saying.

IIRC the heavy chain wrench variety is regularly shown in Car Mechanics magazine /independent manuals and IIRC even in the Citroen workshop manual alomg with the continuous band variety - If I'm wrong regarding the Cit manaul so be it - I don't have time now to check...

Andrew

mezuk04 · Post by **mezuk04** » 24 Jan 2006, 12:15

Yes I realized my mistake with regard to the car ramps, i shall hopefully be doing all the filters aswell, but first job is to get the spheres done which have arrived at work this morning

.....but i wont be putting the car on ramps for the spheres

AndersDK · Post by **AndersDK** » 24 Jan 2006, 17:52

Simon & Andrew _

Yeah right - lets settle on disagreeing

There is nothing like differing opinions & experiences to move you on. Thats how humans invents when they team up

jeremy · Post by **jeremy** » 24 Jan 2006, 18:00

mezuk - Citroen don't recomment changing the tank filters - at any rate for the BX - they simply say wash them in petrol and re-use. Thye also advise petrol as the fluid for washing the reservoir - and while it seems dear - its cheaper than most solvents.

mezuk04 · Post by **mezuk04** » 24 Jan 2006, 18:03

Jeremy - Dont worry when i mentioned 'filters' i was referring to the every 5000 service filters (Well all of them as in fuel, air, pollen and oil) NOT the LHM filters.

Although these were cleaned with Brake Fluid cleaner a few months ago and the tank/reservoir when we did a LHM change since it was orange

soupy_sam · Post by **soupy_sam** » 17 Feb 2006, 15:24

Exactly where is this little screw valve please

mezuk04 wrote:Thanks for that Anders, I have just ordered the tool with the link you have provided.

Can you confirm that its a case of

1. Ride height to minimum (I shall be putting the car onto car ramps at the front).
2. Turn off the engine.
3. Release the pressure by the little screw valve at the front (only half a turn as to not lose the ball) and then tighten the valve back up.
4. Loosen them using the "new" tool I have just ordered.
5. Put a bit of LHM round the seal of the new spheres and hand tighten them into position.
6. Start the car, down the ramps and enjoy the nice new improved ride??

Is it a good idea to keep some spare LHM handy due to the spillage thats required to replace this or isnt it necessary?

Ive browsed the other threads but they never seem to answer the questions i specifically need for my own personal level of competence

Kowalski · Post by **Kowalski** » 17 Feb 2006, 17:16

soupy_sam wrote:Exactly where is this little screw valve please

Its a 12 or 13mm bolt on the pressure regulator (the bit the accumulator sphere screws into).

The Haynes BOL shows where it is (or at least thats how I found it originally).

soupy_sam · Post by **soupy_sam** » 17 Feb 2006, 17:35

All done 10 minutes thanks guys

john alexander · Post by **john alexander** » 17 Feb 2006, 19:54

Hi as a welder for 33 years I wouldn't advise welding a lug on to a sphere, it might still have some pressure in it. you could end up in a&e getting your own lug fitted back on, thats if they find your head. my wife's dad was injured in an accident when he was told to cut the end off a steel tube with a lathe.The tube was pressurised , he ended up deaf and the lathe was destroyed.

dnsey · Post by **dnsey** » 17 Feb 2006, 20:51

I wouldn't advise welding a lug on to a sphere, it might still have some pressure in it.

Besides, most of the spheres which would 'benefit' are in places where there's not enough clearance to remove them if they had a lug fitted. You'd have to grind the lug off again once they'd 'cracked' - more hassle than it's worth IMHO.

bxbodger · Post by **bxbodger** » 17 Feb 2006, 21:07

Steel chain tools are in fact dangerous to use on circular steel members to be unscrewed.

Not with this!!!!Resistance is futile!!!!

I would agree though that the rubber seal can grip ferociously tightly- the sphere should never be tightened more than light hand pressure only, about the same as an oil filter............and we all know how difficult it can be to shift an overtightened oil filter: even sometimes with the leverage of a screwdriver rammed through it!!! I'm always amazed when working on other peoples cars how tight an oil filter can get.