Bleeding silicone brake fluid
Ian
I'm recommissioning my Herald at the moment. After a certain amount of
swithering, I decided to go for silicone fluid in the brake and
clutch. The clutch, which I did first, was fine. However, the brakes
have been a real pain. After a first session, with almost a litre of
fluid through the system the pedal was still very springy. A second
session a week later improved things a bit. A third session today
shows no bubbles at all emerging, but there is still a fair bit of
spring in the pedal.
However ... I also have new shows and pads, which always adds a bit of
bounce on the Herald till things bed in
And ... I have read claims that silicone fluid is a bit more
compressible than glycol
So ... should I be worried? Have folk here had problems bleeding
silicone fluid? Experience of it giving more spring to the pedal?
Shall I just take the car out for a drive - the MOT station is 20
miles away over twisting moorland roads - and hope that everything
firms up a bit.
Incidentally, I know that I could switch to glycol, but my reasons for
silicone are fairly good, and I'd like to stick with it unless it
simply isn't going to be possible to get satisfactory performance.
Ian
PS New master cylinder, calipers, rear cylinders, hoses (Goodrich) and
most pipes.
Harry Bloomfield
> The clutch, which I did first, was fine. However, the brakes
> have been a real pain. After a first session, with almost a litre of
> fluid through the system the pedal was still very springy. A second
> session a week later improved things a bit. A third session today
> shows no bubbles at all emerging, but there is still a fair bit of
> spring in the pedal.
Does it have a servo and you are testing it with the engine running?
If so they can feel a little soft and springy with the servo working,
try it again without. Its to do with you applying much more pressure on
the pedal than you would when actually driving.
--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk
Rob
Personally I don't like silicon fluid not worth the expense. If you
correctly flush your fluid every two years you should have no problems,
except wear and tear on the system components, which is normal what ever
the fluid you use.
Ok having had my rant, make sure that the rear brake shoes are adjusted
fully up, this can induce soft brakes, these should also be adjusted up
after the linings bed in.
After the system has been bleed let the car sit and check the pedal next
day. You may check the play in the rod on the pedal and adjust that up
as well.
r
chongqing....@gmail.com
wrote:
Make sure the shoes are adjusted properly, have you tried bleeding
with the shoes backed off, then adjusting the shoes to the correct
postion?
Also make sure that all seals in the system are happy with silicone
fluid, silicone fluid is not reccomended for my Morris Minor because
it is said it can damage the seals.
Ian
> Personally I don't like silicon fluid not worth the expense. If you
> correctly flush your fluid every two years you should have no problems,
> except wear and tear on the system components, which is normal what ever
> the fluid you use.
Like I said, it was a close call, and if all else fails I'll go back
to glycol.
> Ok having had my rant, make sure that the rear brake shoes are adjusted
> fully up, this can induce soft brakes, these should also be adjusted up
> after the linings bed in.
They're as well adjusted as any new shoes in new drums can be - I'll
certainly expect to re-adjust them after everything has bedded in.
> After the system has been bleed let the car sit and check the pedal next
> day. You may check the play in the rod on the pedal and adjust that up
> as well.
No adjustment at the pedal or in the cylinder. However, leaving the
car to sit for a few days after the first bleed did seem to improve
things a bit - mainly, I think, by allowing microbubbles to coalesce
into bigger, bleedable lumps of air.
I've done some limited road testing and the brakes work OK, without
pulling - it's just that the pedal feels bouncier than I'd like. And,
I fear, than the MOT tester will like ...
Ian
Ian
>
> > The clutch, which I did first, was fine. However, the brakes
> > have been a real pain.
> Does it have a servo and you are testing it with the engine running?
No servo - just a bog standard Herald system.
Ian
Jim Warren
> Dear All,
>
> I'm recommissioning my Herald at the moment. After a certain amount of
> swithering, I decided to go for silicone fluid in the brake and
> clutch. The clutch, which I did first, was fine. However, the brakes
> have been a real pain. After a first session, with almost a litre of
> fluid through the system the pedal was still very springy. A second
> session a week later improved things a bit. A third session today
> shows no bubbles at all emerging, but there is still a fair bit of
> spring in the pedal.
>
> However ... I also have new shows and pads, which always adds a bit of
> bounce on the Herald till things bed in
>
> And ... I have read claims that silicone fluid is a bit more
> compressible than glycol
>
> So ... should I be worried? Have folk here had problems bleeding
> silicone fluid? Experience of it giving more spring to the pedal?
I have got silicone fluid in my PI - it wasn't my choice, the previous
owner put it in after a complete brake overhaul.
And at the time I bought the PI, I had a 2000 with ordinary brake fluid.
And there was *always* a different feel to the PI brakes. The systems
are pretty well identical except the PI has a vacuum storage thing and
the 2000 didn't, and both stopped well enough to get MOTs, but the PI
pedal never felt as solid as the 2000 one.
When I had to replace one of the brake parts for an MOT, I let the
garage do it for the cheap retest, and provided a bottle of DOT5 to make
sure he used the right stuff. It got the MOT, but when I collected the
car afterwards the pedal felt even more spongy than before. I used it
for a week or so, then decided I really didn't like it so took it back
for him to bleed again. It was better second time, but still not as
good as it had been when I bought it. A third bleed a month later
finally fixed it.
Apparently, silicone fluid gets "micro-bubbles" which are too small to
see in the bleed jar but affect the braking system. You have to leave
the system unused for long enough for these micro-bubbles to coalesce
into larger ones and then bleed them out.
My advice is to leave your Herald undriven for at least a week, then
bleed again. Provided after that you get brakes without the pedal going
so far down that you feel inclined to pump it, then it is safe to drive,
it should get an MOT, and you need to do some driving to bed in the new
pads and shoes. Once you are happy that they are bedded in, adjust them
then leave the car as long as is practical without using it, and then
bleed again. The pedal will still feel a little bit springy - it is a
characteristic of silicone - but that last bleed should make it as good
as it will get. And it should then stay like that for years!
Jim
Willy Eckerslyke
I was about to say that'll be the same as my Vitesse then - unless yours
is drums all round. I never had a problem with silicon and don't
remember any great difficulties bleeding the system. But perhaps I was
less sensitive to any sponginess than you are.
I'd certainly recommend you persevere rather than switching back to
normal brake fluid.
Ian
> My advice is to leave your Herald undriven for at least a week, then
> bleed again. Provided after that you get brakes without the pedal going
> so far down that you feel inclined to pump it, then it is safe to drive,
> it should get an MOT, and you need to do some driving to bed in the new
> pads and shoes. Once you are happy that they are bedded in, adjust them
> then leave the car as long as is practical without using it, and then
> bleed again. The pedal will still feel a little bit springy - it is a
> characteristic of silicone - but that last bleed should make it as good
> as it will get. And it should then stay like that for years!
Thanks Jim - much appreciated.
Ian
Mrcheerful
If the problem is micro bubbles, then the answer we found (on motorcycles)
is to pressurise the system and leave it pressurised over night, the
reduction in pedal travel the next day is quite amazing.
I use a brake pedal jack (home made from a mastic gun) to hold the pedal
down. Also useful for checking brake equality and brake lights !!
Mrcheerful
Ian
> If the problem is micro bubbles, then the answer we found (on motorcycles)
> is to pressurise the system and leave it pressurised over night, the
> reduction in pedal travel the next day is quite amazing.
>
> I use a brake pedal jack (home made from a mastic gun) to hold the pedal
> down. Also useful for checking brake equality and brake lights !!
Splendid idea. I shall investigate a bodge along those lines!
Ian
Willy Eckerslyke
> If the problem is micro bubbles, then the answer we found (on motorcycles)
> is to pressurise the system and leave it pressurised over night, the
> reduction in pedal travel the next day is quite amazing.
When I mentioned the trouble I'd had bleeding the front brakes of my
Landy (notoriously difficult) to the MOT tester, he said that he always
gravity bled them - i.e. opened the bleed nipples and just let the fluid
run through on its own for an hour or so. I've never tried this, but
guess it would avoid the problem of micro bubbles.
A web search suggested reverse bleeding them by forcing fluid into the
bleed nipples via a syringe, but I'd already sorted them by then. Dunno
if that method would help the OP.
> I use a brake pedal jack (home made from a mastic gun) to hold the pedal
> down. Also useful for checking brake equality and brake lights !!
Nice idea, and less hassle than searching around for a length of wood
then trying to jam it against the seat back!
Jim Warren
> Mrcheerful wrote:
> >
>> I use a brake pedal jack (home made from a mastic gun) to hold the pedal
>> down. Also useful for checking brake equality and brake lights !!
>
> Nice idea, and less hassle than searching around for a length of wood
> then trying to jam it against the seat back!
For checking brake lights I use a KrookLock. Adjust to length then lock
with the key and jam it between pedal and front seat frame.
Jim
Pete M
I've got a mirror on the garage wall. Just back up and have a look.
--
Pete M - OMF#9
BMW 325i SE Touring
Range Rover V8 Turbo
"Wait! We can't stop here, this is Bat Country"
Andy Dingley
> I'm recommissioning my Herald at the moment. After a certain amount of
> swithering, I decided to go for silicone fluid in the brake and
> clutch. The clutch, which I did first, was fine.
Bigger pipes on the clutch. Silicone is a problem because of surface
tension issues meaning that bubbles won't come off the pipe surface as
easily, especially if there's more pipe area / volume. The trick is:
* Don't put bubbles in there. Use fluid that has sat in the bottle and
settled out, then pour it gently.
* Pressure bleed it gently, rather than pogoing on the pedal. The
Gunson pressure bleeder is cheap enough and works fairly well. Run it
from a spare tyre at no more than about 15psi. It also doesn't work on
Alfa Romeos or other cars where the fluid-loss warning switch fits
through a notch cut in the reservoir next (remove the switch, slip a
collar of bike inner tube over it).
I have four Gunsons, as it's the only way I could ever bleed my
fscking Rangie.
Dave Plowman (News)
Willy Eckerslyke <oss108...@bangor.ac.uk> wrote:
> I was about to say that'll be the same as my Vitesse then - unless yours
> is drums all round. I never had a problem with silicon and don't
> remember any great difficulties bleeding the system. But perhaps I was
> less sensitive to any sponginess than you are.
> I'd certainly recommend you persevere rather than switching back to
> normal brake fluid.
I'm not convinced. Provided you change ordinary brake fluid regularly -
perhaps every couple of years - the parts should have a long life. And
changing the fluid and the subsequent bleeding forces you to examine the
condition of the hoses and pipes.
--
*When the going gets tough, use duct tape
Dave Plowman da...@davenoise.co.uk London SW
To e-mail, change noise into sound.
Willy Eckerslyke
>> I'd certainly recommend you persevere rather than switching back to
>> normal brake fluid.
>
> I'm not convinced. Provided you change ordinary brake fluid regularly -
> perhaps every couple of years - the parts should have a long life.
But realistically, how many of us want to change the fluid that often?
Now that he's bought the stuff, and the cost factor is gone, I can't see
any reason not to stick with it. I'm certainly not convinced that the
system will feel noticeably different once properly sorted, and am also
dubious that the trouble he's been having so far is down to the type of
fluid.
> And
> changing the fluid and the subsequent bleeding forces you to examine the
> condition of the hoses and pipes.
ISTR the OP said he'd fitted steel braided hoses, so inspecting _them_
won't tell him much anyway.
Mike G
"Dave Plowman (News)" <da...@davenoise.co.uk> wrote in message
news:4fd65f4...@davenoise.co.uk...
> In article <6hn66fF...@mid.individual.net>,
> Willy Eckerslyke <oss108...@bangor.ac.uk> wrote:
>> I was about to say that'll be the same as my Vitesse then -
>> unless yours
>> is drums all round. I never had a problem with silicon and
>> don't
>> remember any great difficulties bleeding the system. But
>> perhaps I was
>> less sensitive to any sponginess than you are.
>> I'd certainly recommend you persevere rather than switching
>> back to
>> normal brake fluid.
>
> I'm not convinced. Provided you change ordinary brake fluid
> regularly -
> perhaps every couple of years - the parts should have a long
> life. And
> changing the fluid and the subsequent bleeding forces you to
> examine the
> condition of the hoses and pipes.
I'm with you. I really can't see the point of changing to a
silicone based fluid. DOT 5.1 has many of the advantages of DOT 5
IMO, without any of the potential problems.
AIUI DOT 5 is not compatible with glycol based brake fluid, so
unless a glycol based system is completely purged of any traces
of the old fluid, any remaining 'could' cause problems.
There could also be a problem with the seals themselves on an
older system, as apart from the incompatibility of the fluid
itself, early seals were not chemically resistant to silicone
based fluid, meaning all the seals had to be changed for ones
that were.
Having said that, AFAIK all later manufactured seals are
compatible with both types of fluid, but if the seals have been
replaced with NOS seals it could still be worth checking.
Mike.
Willy Eckerslyke
> I'm with you. I really can't see the point of changing to a silicone
> based fluid. DOT 5.1 has many of the advantages of DOT 5 IMO, without
> any of the potential problems.
We keep hearing about the potential problems, but always from people who
have never apparently used the stuff.
I agree that it'd be a mistake to switch to it from conventional fluid,
but on a rebuilt system where all the seals have been replaced, I really
can't see why not. That's what I did with my Vitesse and it's been
perfect. Cost-wise, what's an extra 15 quid when you're probably
spending 100+ quid on parts anyway? And if it's really an issue, you'll
save by not having to replace the fluid every few years anyway.
Spongy pedal feel? Not in my experience.
Advantages - knowing your brake system will come apart when you want it
to without revealing a mess of rusted calliper pistons, etc; No damage
to paintwork from spills so your carefully restored bulkhead can stay
looking that way.
> AIUI DOT 5 is not compatible with glycol based brake fluid, so unless a
> glycol based system is completely purged of any traces of the old fluid,
> any remaining 'could' cause problems.
Officially, it shouldn't happen as the DOT ratings insist that all
fluids can be mixed. But, I agree that it's best avoided.
> There could also be a problem with the seals themselves on an older
> system, as apart from the incompatibility of the fluid itself, early
> seals were not chemically resistant to silicone based fluid, meaning all
> the seals had to be changed for ones that were.
> Having said that, AFAIK all later manufactured seals are compatible with
> both types of fluid, but if the seals have been replaced with NOS seals
> it could still be worth checking.
AIUI, seals are only prone to damage from silicon fluid if they've
already been exposed to conventional brake fluid, so _unused_ old stock
ones are OK.
The funny thing with all this, is that if we'd we always used silicon
fluid, the huge disadvantages of glycol based fluid would see it used
only by genuine racers and the Max Power brigade while the rest of us
would avoid it like the plague. And newsgroups would be full of doom
mongers telling everyone to stick to DOT5!
Jim Warren
> We keep hearing about the potential problems, but always from people who
> have never apparently used the stuff.
> I agree that it'd be a mistake to switch to it from conventional fluid,
> but on a rebuilt system where all the seals have been replaced, I really
> can't see why not. That's what I did with my Vitesse and it's been
> perfect. Cost-wise, what's an extra 15 quid when you're probably
> spending 100+ quid on parts anyway? And if it's really an issue, you'll
> save by not having to replace the fluid every few years anyway.
> Spongy pedal feel? Not in my experience.
Nor mine "Slightly springy" is how I would describe it, but it is only
noticeable if you regularly alternate between a car with silicone fluid
and one with glycol fluid. If you only drive the DOT5 one, you stop
noticing anything after the first few days and it always feels perfectly
normal after that.
And let us not forget that the OP has *already* renewed his entire
braking hydraulics and filled it with silicone, so changing back is not
a realistic option. The merits of one over the other is only of
academic interest to most. Whatever the system is filled with, it will
stay filled with unless and until there is cause to do wholesale
replacements.
Jim
Rob
> The funny thing with all this, is that if we'd we always used silicon
> fluid, the huge disadvantages of glycol based fluid would see it used
> only by genuine racers and the Max Power brigade while the rest of us
> would avoid it like the plague. And newsgroups would be full of doom
> mongers telling everyone to stick to DOT5!
If I assemble brake components I use a liquid silicon, and run a normal
glycol brake fluid. - Calipers, master cylinders and rear cylinders.
So I have a mix to start.I have no problem with mixing the two.
Where does the problem start with the mixture and why does one have to
ensure the integrity of the fluid, where does it start to fail and how?
r
moray
"Willy Eckerslyke" <oss108...@bangor.ac.uk> wrote in message
news:6hqbvkF...@mid.individual.net...
There is one major disadvantage with Silicon fluid though. It's not
hygroscopic.
This means that any moisture that gets in to the system, will gather, and
eventually work it's way to the lowest point in the system, which is
typically the brake calipers/cylinders. Where it'll then sit, until the
brake caliper/cylinder reaches the boiling point of water, then boil in to
steam, giving you some nice brake fade until things cool down again.
However, flushing the brake fluid out won't get rid of that water sitting in
the bottom of the caliper/cylinder, as the bleed nipple is at the top.
Hygroscopicity is the main advantage of conventional brake fluids. It may
sound like a major weakness, but the fact it absorbs water is an advantage.
Rather than the above scenario, any moisture gets absorbed into the brake
fluid, where it gradually lowers the boiling point of the entire system
(unless of course the brake fluid becomes saturated), and by routine
maintenance (ie changing the fluid every two years), the brake fluid boiling
point should never drop below critical levels. Plus 90+% of any moisture
should get flushed out with a fluid change.
Ian
> There is one major disadvantage with Silicon fluid though. It's not
> hygroscopic.
The same goes for LHM, and I'm not aware of any dreadful problems
caused by moisture in Citroen (and other) systems using it.
Ian
Adrian
were saying:
>> There is one major disadvantage with Silicon fluid though. It's not
>> hygroscopic.
> The same goes for LHM, and I'm not aware of any dreadful problems caused
> by moisture in Citroen (and other) systems using it.
Indeed. It's a bloody big ADVANTAGE, not a disadvantage.
moray
"Ian" <ian.g...@btinternet.com> wrote in message
news:8fc745a6-65bf-4241...@c65g2000hsa.googlegroups.com...
Modern hydraulic power brake systems will still work with air in the system,
albeit with a delay in the time taken for them to apply/release while any
air/vapour is compressed/expanded. This is due to the fact the pump pressure
acts directly on the braking system, and doesn't rely on a fixed
displacement once the pedal is pressed.
Ian Dalziel
Modern?
--
Ian D