Right and wrong hydraulic fluid

What experience have people got of LR hydraulic cylinders and various clutch
fluids?
My Lucus clutch parts came with instructions that said "only use with Lucus
DOT 4 or 5.1 fluid". The modern LHM+ hydraulic fluid in my garage says "not
compatible with DOT fluid systems, could cause failure".

I've heard that new spec fluids will attack old style natural rubber seals,
but do Lucus still use natural rubber? What fluids do other people use? Have
you ever dissolved clutch seals by using the wrong fluid?

My ongoing clutch problems are becoming a religious obsession. Soon I will
reach enlightenment and adopt the title God of Clutch, until then I am a
clutch infidel.
Pleae teach me.

David

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DavidM djm81NOSPAMatcam.ac.uk

On Mon, 11 Oct 2004 11:56:18 +0100, "DavidM" <djm81@(I hate
spam)cam.ac.uk> wrote:

>What experience have people got of LR hydraulic cylinders and various clutch
>fluids?
>My Lucus clutch parts came with instructions that said "only use with Lucus
>DOT 4 or 5.1 fluid". The modern LHM+ hydraulic fluid in my garage says "not
>compatible with DOT fluid systems, could cause failure".
>
>I've heard that new spec fluids will attack old style natural rubber seals,
>but do Lucus still use natural rubber? What fluids do other people use? Have
>you ever dissolved clutch seals by using the wrong fluid?
>

LHM is a mineral hydraulic fluid, which must be used in vehicles with
hydromatic suspension, such as Citroens, Rolls-royce Shadows, etc.
Using DOT in these systems will wreck the seals, resulting in a
expensive repair bill

DOT3/4/5 are synthetic, and are suitable for use in normal
brake/clutch systems. Systems designed for DOT are not normally
suitable for LHM, and using LHM may result in seal failure. Whilst not
an expensive repair on a vahicle such as a Series or 90/110, brake
failure is not something you want to happen whilst youre driving.

DOT3 is a rather old spec now, but more than suitable for older cars
such as Series/90/110. DOT 3,4 and 5 are backwards compatible with
each other, so a system designed for DOT3 will run quite happily on
DOT4 or 5. However, if a system is designed for DOT5 then do not use 3
or 4. DOT5/5.1 is a very high spec oil and is unlikely to be required
in any normal car over about 5 years old, it is designed for high
performance use. DOT4 is usually suitable for most cars. Certainly
it's not worth paying DOT5 prices if your car doesn't need it.

Alex

"Alex" <[email protected]> wrote in message
news:[email protected]...
>> LHM is a mineral hydraulic fluid, which must be used in vehicles with
>> hydromatic suspension, such as Citroens, Rolls-royce Shadows, etc.
>> Using DOT in these systems will wreck the seals, resulting in a
>> expensive repair bill
>>
>> DOT3/4/5 are synthetic, and are suitable for use in normal
>> brake/clutch systems. Systems designed for DOT are not normally
>> suitable for LHM, and using LHM may result in seal failure. Whilst not
>> an expensive repair on a vahicle such as a Series or 90/110, brake
>> failure is not something you want to happen whilst youre driving.
>>
>> DOT3 is a rather old spec now, but more than suitable for older cars
>> such as Series/90/110. DOT 3,4 and 5 are backwards compatible with
>> each other, so a system designed for DOT3 will run quite happily on
>> DOT4 or 5. However, if a system is designed for DOT5 then do not use 3
>> or 4. DOT5/5.1 is a very high spec oil and is unlikely to be required
>> in any normal car over about 5 years old, it is designed for high
>> performance use. DOT4 is usually suitable for most cars. Certainly
>> it's not worth paying DOT5 prices if your car doesn't need it.
>>
>> Alex

Thankyou, very useful info. I'll make sure it is DOT from now on.
You live and learn.

David

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DavidM djm81NOSPAMatcam.ac.uk

DavidM wrote:
> "Alex" <[email protected]> wrote in message
> news:[email protected]...
>>> LHM is a mineral hydraulic fluid, which must be used in vehicles
>>> with hydromatic suspension, such as Citroens, Rolls-royce Shadows,
>>> etc. Using DOT in these systems will wreck the seals, resulting in
a
>>> expensive repair bill
>>>
>>> DOT3/4/5 are synthetic, and are suitable for use in normal
>>> brake/clutch systems. Systems designed for DOT are not normally
>>> suitable for LHM, and using LHM may result in seal failure. Whilst
>>> not an expensive repair on a vahicle such as a Series or 90/110,
>>> brake failure is not something you want to happen whilst youre
>>> driving.
>>>
>>> DOT3 is a rather old spec now, but more than suitable for older
cars
>>> such as Series/90/110. DOT 3,4 and 5 are backwards compatible with
>>> each other, so a system designed for DOT3 will run quite happily
on
>>> DOT4 or 5. However, if a system is designed for DOT5 then do not
>>> use 3 or 4. DOT5/5.1 is a very high spec oil and is unlikely to be
>>> required in any normal car over about 5 years old, it is designed
>>> for high performance use. DOT4 is usually suitable for most cars.
>>> Certainly it's not worth paying DOT5 prices if your car doesn't
>>> need it.
>>>
>>> Alex
>
> Thankyou, very useful info. I'll make sure it is DOT from now on.
> You live and learn.
>
> David

But get it absolutely correct though!
DOT [US Department of Transport] 3, 4 or 5.1 are compatible. DOT 5 is
NOT compatible with these, so beware. Most brake fluids are DOT 4 or,
rarely 5.1.

LHM is seldom used in car brakes though it is commonly used in heavy
plant vehicles and tractors, though these may sometimes use ATF or
Super Universal oil.

Using the wrong fluid in your system is extemely costly and ultimately
dangerous.

Huw


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On or around Mon, 11 Oct 2004 16:34:15 +0100, "Huw"
<hedydd[nospam]@tiscali.co.uk> enlightened us thusly:
>
>But get it absolutely correct though!
>DOT [US Department of Transport] 3, 4 or 5.1 are compatible. DOT 5 is
>NOT compatible with these, so beware. Most brake fluids are DOT 4 or,
>rarely 5.1.

I was about to say that. well done DOT for screwing up the system.

DOT 5 is (AFAIK) Silicone fluid used in racing brake systems. DOT 5.1 is
the next in the sequence of DOT 3, DOT 4 etc.

The main thing is that as you go up the DOT numbers, the spec of the fluid
in such areas as boiling point and resistance to hygroscopy (absorbing
water) increases - some modern brake systems may get too hot for DOT 3 to
handle, and you *really* don't want to boil the fluid halfway through an
emergency stop...

>LHM is seldom used in car brakes though it is commonly used in heavy
>plant vehicles and tractors, though these may sometimes use ATF or
>Super Universal oil.

from memory, about the only thing that uses LHM is most of the hydropneumo
Citroens (some use LHS - Liquide Hydrolique Synthetique, as opposed to
Minerale for LHM) which use it in the suspension and the brakes - the
systems are combined - and (some) Rolls-Royce which have a power-braking
system on similar lines, I believe.

Putting brake fluid in an LHM system knackers it just as well as LHM in one
designed for normal brake fluid, from what I hear. You can, in an
emergency, use different fluid in a Citroen, but only for a short time and
it should be flushed and replaced with LHM ASAP.

>Using the wrong fluid in your system is extemely costly and ultimately
>dangerous.

quite.

I tend to go with DOT 4 in everything these days, although you can still get
DOT 3 it ain;t common and it ain't worth it.

Mind, some very old brake systems use Girling Crimson fluid (I'm thinking S1
brakes here) and I'm not sure without looking whether those systems are
compatible with DOT 3.

Huw wrote:

> DavidM wrote:
>> "Alex" <[email protected]> wrote in message
>> news:[email protected]...
>>>> LHM is a mineral hydraulic fluid, which must be used in vehicles
>>>> with hydromatic suspension, such as Citroens, Rolls-royce Shadows,
>>>> etc. Using DOT in these systems will wreck the seals, resulting in
> a
>>>> expensive repair bill
>>>>
>>>> DOT3/4/5 are synthetic, and are suitable for use in normal
>>>> brake/clutch systems. Systems designed for DOT are not normally
>>>> suitable for LHM, and using LHM may result in seal failure. Whilst
>>>> not an expensive repair on a vahicle such as a Series or 90/110,
>>>> brake failure is not something you want to happen whilst youre
>>>> driving.
>>>>
>>>> DOT3 is a rather old spec now, but more than suitable for older
> cars
>>>> such as Series/90/110. DOT 3,4 and 5 are backwards compatible with
>>>> each other, so a system designed for DOT3 will run quite happily
> on
>>>> DOT4 or 5. However, if a system is designed for DOT5 then do not
>>>> use 3 or 4. DOT5/5.1 is a very high spec oil and is unlikely to be
>>>> required in any normal car over about 5 years old, it is designed
>>>> for high performance use. DOT4 is usually suitable for most cars.
>>>> Certainly it's not worth paying DOT5 prices if your car doesn't
>>>> need it.
>>>>
>>>> Alex
>>
>> Thankyou, very useful info. I'll make sure it is DOT from now on.
>> You live and learn.
>>
>> David
>
> But get it absolutely correct though!
> DOT [US Department of Transport] 3, 4 or 5.1 are compatible. DOT 5 is
> NOT compatible with these, so beware. Most brake fluids are DOT 4 or,
> rarely 5.1.
>
> LHM is seldom used in car brakes though it is commonly used in heavy
> plant vehicles and tractors, though these may sometimes use ATF or
> Super Universal oil.
>
> Using the wrong fluid in your system is extemely costly and ultimately
> dangerous.
>
> Huw
>
>
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LHM was introduced to automotive use by Citroen in 1967? and has been used
ever since by Citroen in their combined hydraulic systems (brakes,
steering, suspension, gearchange) and a short while later was adopted by
Rolls Royce, who were (are) building the Citroen suspension system under
licence. (As far as I know, no other car makers use it)
This is a mineral oil, and replaced LHS2, which was similar to conventional
brake fluid, but higher viscosity among other differences.
The change corresponded to a change from natural rubber based seals, O-rings
etc to synthetic rubber. I think the main advantage of the LHM is that it
is a better lubricant, although the synthetic seals are perhaps not as good
as the natural rubber ones. Note that compared to most cars Citroen
hydraulic systems operate at much higher pressures, and do not use any edge
seals, but use all O-rings. The height control valves do not use seals, but
are made accurately enough not to need them.
JD

On or around Tue, 12 Oct 2004 06:17:13 +1000, JD <[email protected]>
enlightened us thusly:

>Note that compared to most cars Citroen
>hydraulic systems operate at much higher pressures, and do not use any edge
>seals, but use all O-rings. The height control valves do not use seals, but
>are made accurately enough not to need them.

sometimes, I wish i could combine a citroen with a land rover. The citroen
hydraulic system, when in good condition, beats the hell out of anything
else.

all sorts of cunningness is possible: for example, on the BXs I had, the
front brakes are fed from the full-pressure hydraulics, but the back ones
are fed from the return from the rear suspension - thus, the back brakes are
applied proportional to the load on the back suspension. without any extra
gadgets to get out of order.

and, with some modification and longer legs, and maybe bigger spheres, you
could get a beaut of an off-road suspension setup with adjustable height
etc. you can also run ABS systems without an extra pump, since you already
have the high pressure system to work with. In fact, the normal non-abs
brakes haven't got a conventional brake cylinder or anything, the brake
pedal operates a valve which feeds pressure to the calipers.

of course, if you lose the hydraulics, you lose *everything*, but with
suitable attention that rarely happens, and almost always gives some
warning. The system has an "accumulator" sphere as well as the suspension
ones, so even if the pump belt fails, you still have pressure for a short
while, and as soon as pressure drops, that big red "STOP" light comes on on
the dash.

On Mon, 11 Oct 2004 22:04:52 +0100, Austin Shackles
<[email protected]> wrote:

>On or around Tue, 12 Oct 2004 06:17:13 +1000, JD <[email protected]>
>enlightened us thusly:
>
>>Note that compared to most cars Citroen
>>hydraulic systems operate at much higher pressures, and do not use any edge
>>seals, but use all O-rings. The height control valves do not use seals, but
>>are made accurately enough not to need them.
>
>sometimes, I wish i could combine a citroen with a land rover. The citroen
>hydraulic system, when in good condition, beats the hell out of anything
>else.
>

Yeah, untill it goes wrong, then you're completely stuffed. At least
with a broken leaf or coil you've got some chance of remaining mobile.

Alex

In message <[email protected]>, Alex
<[email protected]> writes
>On Mon, 11 Oct 2004 11:56:18 +0100, "DavidM" <djm81@(I hate
>spam)cam.ac.uk> wrote:
>
>>What experience have people got of LR hydraulic cylinders and various clutch
>>fluids?
>>My Lucus clutch parts came with instructions that said "only use with Lucus
>>DOT 4 or 5.1 fluid". The modern LHM+ hydraulic fluid in my garage says "not
>>compatible with DOT fluid systems, could cause failure".
>>
>>I've heard that new spec fluids will attack old style natural rubber seals,
>>but do Lucus still use natural rubber? What fluids do other people use? Have
>>you ever dissolved clutch seals by using the wrong fluid?
>>
>
>LHM is a mineral hydraulic fluid, which must be used in vehicles with
>hydromatic suspension, such as Citroens, Rolls-royce Shadows, etc.
>Using DOT in these systems will wreck the seals, resulting in a
>expensive repair bill
>
>DOT3/4/5 are synthetic, and are suitable for use in normal
>brake/clutch systems. Systems designed for DOT are not normally
>suitable for LHM, and using LHM may result in seal failure. Whilst not
>an expensive repair on a vahicle such as a Series or 90/110, brake
>failure is not something you want to happen whilst youre driving.
>
>DOT3 is a rather old spec now, but more than suitable for older cars
>such as Series/90/110. DOT 3,4 and 5 are backwards compatible with
>each other, so a system designed for DOT3 will run quite happily on
>DOT4 or 5. However, if a system is designed for DOT5 then do not use 3
>or 4. DOT5/5.1 is a very high spec oil and is unlikely to be required
>in any normal car over about 5 years old, it is designed for high
>performance use. DOT4 is usually suitable for most cars. Certainly
>it's not worth paying DOT5 prices if your car doesn't need it.
>
>Alex
Here we are again - who remembers the old Girling v Lucas problems.
--
hugh
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