C5s and DOT4 brake fluid

lolingram · Post by **lolingram** » 20 Aug 2007, 08:12

Anyone any thoughts as to why Citroen reverted to horrid alcohol based DOT brake fluid for C5/C6s?

Seems a real retrograde step...

Post by **CitroJim** » 20 Aug 2007, 13:21

There may be two reasons Lol,

One is that all other PSA group cars now use conventional brakes and thus reasons of economy and the other reason my be due to safety legislation.

The old hydraulic pump/doseur/accumulator system may be seen by legislators as a system having severel single points of failure and thus not truely dual circuit and have effectively been legislated out of existence.

It cannot be because the factory making hydraulic components has shut down as they're still in procuction for Iranian CKD Xantia kits.

Whatever, I agree it is a retrograde step and very regrettable.

It could just be because people don't like the pedal feel and/or cannot cope with the exceptionally efficient brakes...

nick · Post by **nick** » 20 Aug 2007, 14:10

Didn't some Citroens with "normal" brakes use LHM in the system too?

I seem to recall my mum's 1982 Dyane used LHM rather than DOT fluid.

Post by **CitroJim** » 20 Aug 2007, 14:31

nick wrote:Didn't some Citroens with "normal" brakes use LHM in the system too?

I seem to recall my mum's 1982 Dyane used LHM rather than DOT fluid.

They did indeed Nick

I've never understood, nor been given any good reason why conventional glycol based brake fluid is preferred over LHM in any system. Look at brake fluid: it's corrosive, hgroscopic (sp? - absorbs water), a paint stripper , poisionous (I believe) and it seizes nipples. LHM and mineral-based hydraulic fluids have none of those drawbacks. So what is it? cost? or does LHM in comventional brake circuit arrangements have some major drawback I'm not aware of?

Post by **elma** » 20 Aug 2007, 16:28

Isn't the C5 on LHS? Maybe it's got different properties not suitable for brakes.

Post by **CitroJim** » 20 Aug 2007, 17:03

superloopy1 wrote:Citrojim - just had a quick look at your website. Are you planning on pushing out the links to all those little sub-jobbies, hydraulics, calipers etc. Would be damned useful to someone like me, pictures tell a thousand words or so they say ......

Yes, I am!

Time is the enemy at the moment. Keep watching it

Kowalski · Post by **Kowalski** » 20 Aug 2007, 20:06

The simple fact is that PSA has decided to cut costs. It would cost more money to design a LHM or LDS based ABS system with EBD and all of the other features that the 407 has. Even if they went with a conventional system and used LHM or LDS in it (assuming they were suitable) they'd have to change seals and pipe materials, which is a load of cost they don't need to be involving themselves in.

If you wanted a step forward, perhaps a DOT5 silicone based fluid would have been a way forward, but apparently it doesn't work well with ABS and has issues with aeration.

Post by **CitroJim** » 20 Aug 2007, 22:27

Kowalski wrote: If you wanted a step forward, perhaps a DOT5 silicone based fluid would have been a way forward, but apparently it doesn't work well with ABS and has issues with aeration.

You may be on to something there

LHM certainly behaves badly when aerated. Bleeding Xantia brakes after an LHM change can produce a bottle of froth, like a green pint of beer

I've never seen conventional brake fluid froth like LHM can and perhaps yes, Elma, LDS may froth even more badly than LHM does.

AndersDK · Post by **AndersDK** » 21 Aug 2007, 00:31

elma wrote:Isn't the C5 on LHS? Maybe it's got different properties not suitable for brakes.

Not LHS - but LDS.

LHS was the old red stuff used in pre '67 D-models.

The latest type LDS (Liquide Direction & Suspension) fluid is not compatible with either LHS, LHM or DOT3/4 fluids.

Donno what kind of fluid LDS really are, but I'm pretty sure we'll soon learn how its composed, at least to know its base fluid type.

Mandrake · Post by **Mandrake** » 21 Aug 2007, 07:27

citrojim wrote: You may be on to something there LHM certainly behaves badly when aerated. Bleeding Xantia brakes after an LHM change can produce a bottle of froth, like a green pint of beer

Thats caused by the pump losing its prime when you disconnect the feed line to the pump and/or lift the centre out of the tank, causing a large air pocket to be sucked in by the pump, airated, and then returned to the tank and/or into the system.

The trick to prevent that getting into the rest of the system is to make sure to always start with the bleed screw open after doing an LHM change, let it idle a couple of minutes for the air to circulate out and the frothing in the tank to die down, and if you're really paranoid let it stand for 10-15 minutes with the engine off before closing the bleed screw and pressurizing as normal. This way you won't get any bubbles into the hydraulic system at all...

I've never seen conventional brake fluid froth like LHM can and perhaps yes, Elma, LDS may froth even more badly than LHM does.

Conventional brake fluid has no magic anti-froth properties, it's just not subjected to the kind of scenario described above where its being pumped through a high pressure pump along with a mixture of air when the system is being primed...

Regards,
Simon

Mandrake · Post by **Mandrake** » 21 Aug 2007, 07:30

AndersDK wrote:Donno what kind of fluid LDS really are, but I'm pretty sure we'll soon learn how its composed, at least to know its base fluid type.

Indications are that LDS is a synthetic mineral compatible oil - and that seals and sphere diaphrams between LHM and LDS systems are in fact compatible with each other. No hard evidence yet though, and I forget the source of this information, so take it with a grain of salt.

Regards,
Simon

lolingram · Post by **lolingram** » 21 Aug 2007, 08:08

citrojim wrote:
nick wrote:Didn't some Citroens with "normal" brakes use LHM in the system too?

I seem to recall my mum's 1982 Dyane used LHM rather than DOT fluid.
They did indeed Nick

I've never understood, nor been given any good reason why conventional glycol based brake fluid is preferred over LHM in any system. Look at brake fluid: it's corrosive, hgroscopic (sp? - absorbs water), a paint stripper , poisionous (I believe) and it seizes nipples. LHM and mineral-based hydraulic fluids have none of those drawbacks. So what is it? cost? or does LHM in comventional brake circuit arrangements have some major drawback I'm not aware of?

My son worked 18 years for Lewmar - boat winches, bowthrusters and windlasses mostly hydraulically driven. Nothing but minerals used.

AndersDK · Post by **AndersDK** » 21 Aug 2007, 11:01

Mandrake wrote:
AndersDK wrote:Donno what kind of fluid LDS really are, but I'm pretty sure we'll soon learn how its composed, at least to know its base fluid type.
Indications are that LDS is a synthetic mineral compatible oil - and that seals and sphere diaphrams between LHM and LDS systems are in fact compatible with each other. No hard evidence yet though, and I forget the source of this information, so take it with a grain of salt.

Regards,
Simon

The new style C5 & C6 (grey painted) spheres are backwards compatible with LHM Xantiae - so some relationship to mineral based oils must exists.

Its quite funny what Citroen mechanics are lead to tell customers - to be sure they come back even for simple LDS level checks and top-ups :
"The new LDS fluid is very poisoning and dangerous. You must wear gloves when handling it. Dont try purchase this stuff elsewhere."
o*-.Spoken by a Citroen mechanic on a DK Citroen forum.-*o

lolingram · Post by **lolingram** » 21 Aug 2007, 11:11

AndersDK wrote:
Mandrake wrote:
AndersDK wrote:Donno what kind of fluid LDS really are, but I'm pretty sure we'll soon learn how its composed, at least to know its base fluid type.
Indications are that LDS is a synthetic mineral compatible oil - and that seals and sphere diaphrams between LHM and LDS systems are in fact compatible with each other. No hard evidence yet though, and I forget the source of this information, so take it with a grain of salt.

Regards,
Simon
The new style C5 & C6 (grey painted) spheres are backwards compatible with LHM Xantiae - so some relationship to mineral based oils must exists.

Its quite funny what Citroen mechanics are lead to tell customers - to be sure they come back even for simple LDS level checks and top-ups :
"The new LDS fluid is very poisoning and dangerous. You must wear gloves when handling it. Dont try purchase this stuff elsewhere."
o*-.Spoken by a Citroen mechanic on a DK Citroen forum.-*o

And the truth being.... (so we know!)?

Kowalski · Post by **Kowalski** » 21 Aug 2007, 21:43

AndersDK wrote:The new style C5 & C6 (grey painted) spheres are backwards compatible with LHM Xantiae - so some relationship to mineral based oils must exists.

Its quite funny what Citroen mechanics are lead to tell customers - to be sure they come back even for simple LDS level checks and top-ups :
"The new LDS fluid is very poisoning and dangerous. You must wear gloves when handling it. Dont try purchase this stuff elsewhere."
o*-.Spoken by a Citroen mechanic on a DK Citroen forum.-*o

If it were so dangerous, it would say so on the bottle.

No doubt a material safety data sheet will be available for LDS somewhere or other.