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Thread: Brake fluids?

  1. #1
    Fellow Frogger! Dano's Avatar
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    Default Brake fluids?

    I am sure this topic has been discussed somewhere on this site before, but here goes anyhow.

    What brake fluid should I use in the 404? The web is full of varying opinions, but some firsthand experience would be good.

    From what I can gather, the newer silicone based fluids would be the way to go? I appreciate that the older dot 3, 4 & 5 versions and the newer silicone type cannot are incompatible. But, since the complete hydraulic system will be new, including lines, I do not see a problem. Because the two types arenít compatible, would I need to pull down and clean the new pre-assembled cylinders etc.? I am assuming they were assembled with brake fluid as a lubricant. Or, am I just being too cautious?

    I'd appreciate any advice and recommendations of brands to use. Hopefully, the front callipers will be re-assembled this weekend.

    Cheers,

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    Dan

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    1000+ Posts renault8&10's Avatar
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    Iíd doubt they were assembled with brake fluid, more likely rubber grease but for the small amount they would of used , it could be either rinsed off, or left and not cause a problem. With totally new lines and seals youíre probably in the best position to change to silicon. I use Dot 5 bought in small bottles ~225mls at Harley Davidson dealer parts counters. They are about $25 per bottle and I usually buy 2-3 at a time (2 would probably suffice).

    Prior to that I used to use Dot 4 - usually Castrol. I like the fact the silicon is non-corrosive to paint (or much less so at least) and non hydroscopic so will potentially last longer. In theory it is also reusable if you filter it, but I havenít been that stingy (yet).

    Ps - donít let the pimply 18 yr old in Autobahn, Bursonís etc tell you that Dot 5.1 is the same as Dot 5 but better. Only Dot 5 is silicon based, the others are glycol based and not compatible.
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    Last edited by renault8&10; 26th January 2018 at 11:52 AM.
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    KB


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    1000+ Posts robmac's Avatar
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    Quote Originally Posted by Dano View Post
    I am sure this topic has been discussed somewhere on this site before, but here goes anyhow.

    What brake fluid should I use in the 404? The web is full of varying opinions, but some firsthand experience would be good.

    From what I can gather, the newer silicone based fluids would be the way to go? I appreciate that the older dot 3, 4 & 5 versions and the newer silicone type cannot are incompatible. But, since the complete hydraulic system will be new, including lines, I do not see a problem. Because the two types aren’t compatible, would I need to pull down and clean the new pre-assembled cylinders etc.? I am assuming they were assembled with brake fluid as a lubricant. Or, am I just being too cautious?

    I'd appreciate any advice and recommendations of brands to use. Hopefully, the front callipers will be re-assembled this weekend.

    Cheers,

    Dan
    Definitely use a silicon based fluid if you have new and clean system.

    And note the fact silicon fluid is in use near he master cylinder.

    Any of the name brands are suitable -visit an auto brake supplier or buy Penrite .

    EDIT: I'd add, I've had mixed success with rubber grease. It's good for fitting OEM rubber items that are new and correctly sized.

    However, when fitting a tight non oem substitute part which is "close enough. Bear in mind it makes the item easy to fit: but also easier to slip off as well.
    Last edited by robmac; 26th January 2018 at 12:37 PM.
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    In 1983 we bought a new Nissan and i changed the brake fluid (i think it was made by Dow?) and never changed it in 10 years. I got so curious what the brake system would look like on the inside (b'cause there is the possibility of condensate settling in the lowest part) that i pulled the system apart. Everything looked like new.
    With the older or some silicon brake fluids there can be a comparability problem with rubber so soak the rubbers in the fluid for a couple of days and see if they swell.
    In another car i used BelRay silicon fluid. They claim it mixes with other fluids but i still flushed the system.
    They also claim it's compatible with ABS but i'm not game to put it in the Megane (which is till under warranty) just yet.
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    1000+ Posts PeterT's Avatar
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    I personally think you're better staying clear of silicon and using a quality Dot 4 such as Motul RBF or Wilwood EXP. Most importantly, change it regularly.

    '92 205 Mi16
    '90 Mi16x4

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    1000+ Posts renault8&10's Avatar
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    Quote Originally Posted by PeterT View Post
    I personally think you're better staying clear of silicon and using a quality Dot 4 such as Motul RBF or Wilwood EXP. Most importantly, change it regularly.
    That does depend on intended use Peter. I’m imagining this to be std restored car for tootling around on weekends, not a track car. Horses for courses as they say.
    KB


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    1000+ Posts PeterT's Avatar
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    When did I mention track cars?

    Silicone Brake Fluid

    '92 205 Mi16
    '90 Mi16x4

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    Right on the money about regular change, even for road use

    Years ago had got family 280TE serviced for hols. "Make sure brakes OK, taking a trailer"

    About 1/3 of way down big hill into Huskisson lost brakes. Made it down in one piece by frantic grab for second ( I hate automatics!) and use of handbrake. Arrived at bottom of hill in cloud of brake smoke ( half on all the way down ) and only then told family what was going on ( after changing underwear ). Comment from SWMBO " I thought you were driving even funnier than usual"

    Fluid had not been changed by regular ( soon to be ex ) mechanic and had boiled.

    Important habit, changing the fluid

    Your attached piece on Silicon very useful and interesting. Had been tossing this idea around in my mind for the 4CV, as system will be being renewed from scratch and I now have a little patch of blistered paint under the 404 reservoir after an unnoticed spillage.

    There seems to be something to be said for using parts/consumables as designed and living with the risks

    Many Thanks

    Andrew

    Quote Originally Posted by PeterT View Post
    When did I mention track cars?

    Silicone Brake Fluid

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    1000+ Posts robmac's Avatar
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    I must say, after reading Peter T's link, I'm less inclined to use silicone fluids in classic cars
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    Yep, Now more confused then ever after reading Peter's interesting article. I guess/hope the two pack paint will be a little more resistant to the standard fluid.

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    BelRay claims to have overcome the rubber comparability problem. I've soaked several types of brake rubbers in silicon fluid and only the ones from a Wetczech swelled up like a sponge.
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    I agree with the notion that silicone doesn't belong anywhere near a car or workshop (unless attached to some fair maiden's upper extremities)

    It will contaminate tools, clothes, workshop gloves, rags and containers without being obvious until one want's to paint something.

    Throw anything containing silicone as far away from the workshop as possible, then go find it and throw it even further. This includes silicone sprays, roof and gutter sealants and polish. Even the humble silicone carbide abrasive paper can be a problem when painting.

    Õ know all this from bitter experience.

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    Quote Originally Posted by PeterT View Post
    When did I mention track cars? Silicone Brake Fluid
    Interesting article Peter. There are a few around discussing silicone fluid. And yes, it may not be for everyone and needs approaching properly.

    I'd agree with making the change but with a bit of care and knowledge. In my case, I put silicone fluid (Dow Corning, back then) in my Lockheed drum-braked 1950 Renault 4CV in 1990, and didn't touch the system again until about 2015. That was when I changed the braking system to give it larger drums and different hoses/wheel cylinders. I pulled the older components down and all were perfect after more than 20 years. The car had been used very much intermittently as a classic. This has been the experience of others with these Renaults.

    Then, about 5 years ago, the disc-braked R8 came up for some calliper servicing - the hydroscopic fluids all end up causing corrosion behind the o-ring seal grooves in the callipers, which are alloy. New everything, calliper seal grooves cleaned and polished and all was well. I know of three of these alloy calliper Renaults with silicone fluid and I'm sure there are more. We have had perfect brake performance, and mine is used a lot, not just for odd classic events.

    So, silicone fluid gets the thumbs up for my purposes. I'm hoping it is a long time before high pedal pressures or groaning brakes indicate pistons not moving well in the callipers, now that we have a non-hydroscopic fluid. It certainly lubricates the pistons adequately.

    However, this is a job that needs to be done carefully and properly, and in both cases I took the prevailing advice and changed all rubber components. I did it myself too, so know what was done!

    Personally, it has been very satisfactory. I can't see why you'd change it regularly - perhaps there's a good argument for new brake hoses every few years, based on my experience (and others) of internal deterioration, and then you might change or filter the fluid.

    A related question, rarely raised, is why not to use Citroen's LHM fluid, a mineral-based oil used in a wide range of their from later DS, and CX/Xantia cars up to the C5. Some 2CV brakes run on LHM. It's a lot cheaper than silicone but hadn't occurred to me. It isn't hygroscopic and if it will stop a CX clearly has a high boiling point!

    Cheers
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    Renault 4CV 1951
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    Renault Scenic 2007 (mine)
    Peugeot 306 XT 1995 (daughter's)
    CitroŽn CX Pallas 1980

    National Co-ordinator, Renault 4CV Register of Australia

  14. #14
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    Quote Originally Posted by 59 Floride View Post
    I agree with the notion that silicone doesn't belong anywhere near a car or workshop (unless attached to some fair maiden's upper extremities)

    It will contaminate tools, clothes, workshop gloves, rags and containers without being obvious until one want's to paint something.

    Throw anything containing silicone as far away from the workshop as possible, then go find it and throw it even further. This includes silicone sprays, roof and gutter sealants and polish. Even the humble silicone carbide abrasive paper can be a problem when painting.

    Õ know all this from bitter experience.
    Should have added a "keep the stuff to itself" aspect to my comment. Emphatically yes!!! Terrible stuff for later painting.
    JohnW

    Renault 4CV 1951
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    Peugeot 306 XT 1995 (daughter's)
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    National Co-ordinator, Renault 4CV Register of Australia

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    Problem with LHM, beyond a car designed for it including later 2cv, is that most rubber brake parts are made from EPDM or similar and will not tolerate it. I doubt LDS would be better. This is the same issue people have had with DS suspension boots when mixing parts and fluids. I recall seeing an ID19 on LHS where someone had fitted LHM seals to the rear brakes and it leaked badly after a short period. For a Traction, Franzose advised their seals are intended for Dot4 and are not compatible with LHM. Silicone may be a sane option for that as it has no vacuum booster, used rarely (the main reason for avoiding DOT4) and standard seals can almost certainly be used. Those vacuum pump kits including a bleeder cup attachment cost so little now that having a dedicated unit for bleeding silicone fluid might be a wise move.

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    Quote Originally Posted by David S View Post
    Problem with LHM, beyond a car designed for it including later 2cv, is that most rubber brake parts are made from EPDM or similar and will not tolerate it. I doubt LDS would be better. This is the same issue people have had with DS suspension boots when mixing parts and fluids. I recall seeing an ID19 on LHS where someone had fitted LHM seals to the rear brakes and it leaked badly after a short period. For a Traction, Franzose advised their seals are intended for Dot4 and are not compatible with LHM. Silicone may be a sane option for that as it has no vacuum booster, used rarely (the main reason for avoiding DOT4) and standard seals can almost certainly be used. Those vacuum pump kits including a bleeder cup attachment cost so little now that having a dedicated unit for bleeding silicone fluid might be a wise move.
    Yes, you do need the right rubber! I'm told is it around though if you find the right supplier. Again, it just needs the right attention to detail. LHS/LDS/LHM certainly don't mix from all accounts.

    And, of course, I'm not using silicone on a car with a booster that might leak (WILL leak, in the end....) and suck it internally.
    JohnW

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    Renault Scenic 2007 (mine)
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    Perhaps an inline filter/trap on the engine side of the booster? Contamination should show up easily if it was plastic or glass. Being vacuum, 15psi is the maximum negative pressure it must cope with. Might a glass bowl fuel filter be adapted?

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    It's not. Mine was Glasurit 2-pack

    Didn't take long to bubble

    More fool me for not checking more often ( was leak from clutch cylinder- cap seal below par )

    Andrew

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    Quote Originally Posted by David S View Post
    Perhaps an inline filter/trap on the engine side of the booster? Contamination should show up easily if it was plastic or glass. Being vacuum, 15psi is the maximum negative pressure it must cope with. Might a glass bowl fuel filter be adapted?
    Interesting thought. We have boosters on the Scenics I suppose - rarely lift the bonnets, they being moderns! I'm not touching them, regarding brake fluid, that is for sure. They just go and go and I get them serviced every 6 months or so.
    JohnW

    Renault 4CV 1951
    Renault R8 1965
    Renault Scenic 2005 (wife's)
    Renault Scenic 2007 (mine)
    Peugeot 306 XT 1995 (daughter's)
    CitroŽn CX Pallas 1980

    National Co-ordinator, Renault 4CV Register of Australia

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    Dano, what did you do in the end? Or did the other things in life get in the way, as they do.... ??
    JohnW

    Renault 4CV 1951
    Renault R8 1965
    Renault Scenic 2005 (wife's)
    Renault Scenic 2007 (mine)
    Peugeot 306 XT 1995 (daughter's)
    CitroŽn CX Pallas 1980

    National Co-ordinator, Renault 4CV Register of Australia

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