Amazoning with Silicon Brake Fluid

Ongoing compilation, R. Kwas  (Comments Added)

This is a compilation of the interesting and applicable information I have encountered applicable to the use of DOT 5 silicon Brake Fluid in a vintage Volvo (Girling brake components use EDPM synthetic rubber) ...I intend to add to it as I gather more notes on the subject....naturally, the information presented here is not limited to Amazons, but also applies to its Volvo contemporaries.

DOT Designations and Boiling Points

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First of all:  DOT5.1 is NOT a further development of the Silicon DOT5 fluid as the nomenclature would suggest...you can thank the brainiacs, no, absolute idiots at the DOT for that...this is a MAJOR SCREWUP!  It is in fact of the same formulation and so compatible with DOT4, and not DOT5.  Do not mix DOT3, 4, or 5.1 with DOT5! 

Pros-Big Pros Bolded:

Non-hygroscopic (non-moisture absorbing), no decrease in boiling point with moisture absorption therefore no deterioration over time, no internal corrosion of brake components due to fluid moisture content, no need to periodically change fluid.  

Excellent seal/dust boot compatibility, increased seal life/time between rebuilds by 3 times (conservative estimate from first-hand experience with multiple vehicles), no frozen wheel cylinders or empty reservoirs after prolonged vehicle storage.   Independently conducted fluid compatibility test (under UV) with Girling seals (submerged in fluid PLUS exposed to UV of the sun for a period of 6 months...adding UV energy to any potential reaction in this manner would promote/accelerate it) yielded very good results.  

Inert.  Non paint-attacking in case of spills.  An nicely painted engine compartment will stay nicely painted - especially under the fluid reservoirs.

Cons-Big Cons Bolded:

More compressible at elevated temps, therefore unsuitable for racing.  When silicon fluid first became available, it was heralded as the grooviest thing for all vehicles since a driver...so racers, in their never-ending quest for an advantage tried it and found that at elevated temperatures (a condition they certainly frequently encounter) they would get a soft pedal, making threshold braking difficult if not impossible.  Soooo...Silicon is not suitable for racers or those planning to drive the Mount Washington Auto Road (especially the down trip).

Longer retention of suspended air especially micro-aeration.  This will result in a soft pedal and make repeated system bleeding necessary.  Care must be taken during fluid handling to minimize aeration.  Micro-aeration can occur in rear brake valve during fluid change-over, necessitating repeated system bleeding .

Non-compatible/mixable with other (DOT3/4) fluids.  System must be flushed for fluid change-over.  Top-up fluid should be kept on-board as it may not readily available or be expensive, top-up container should be kept absolutely full to prevent road-vibration caused fluid aeration.  Reservoirs must be clearly marked to prevent topping up with incorrect/incompatible fluid.

Expensive, typical cost is 2-3 times that of DOT4 fluid, but as it does not need to be replaced it breaks even (if not better) over the long haul.  Upon last inquiry, 16oz. were quoted at $8USD (had to be ordered, 2-3 day wait).

Unknowns -To Be Researched:

1.  Affects on motor if ingested and combusted (due for instance to failure of brake vacuum assist unit diaphragm).

Current Sources: 

Few parts houses stock it on shelves, but most can still easily get it on special order.  Eastwood, the restoration specialty supplier out of Pennsylvania used to carry it, but upon last check had discontinued it.  Pooooo

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Reservoirs clearly marked to prevent topping up with  incorrect/incompatible fluid.

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Notes, and my wise*** incredibly intuitive (and obvious!) comments highlighted in yellow.

DOT Designations and Boiling Points Requirements (º Fahrenheit)

from:  http://www.raceshopper.com/brake_fluid_faq.shtml

Notice DOT5 is not listed!!

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UPDATE Nov 2022:  It's been a while since I've updated this page, so here are applicable Random Excerpts and responses to threads on Fora:

 Link to Brake Bleeding Thread:    http://www.volvoforums.org.uk/showthread.php?t=254659 addidition/clarifications added

My post to Thread:

DOT 4 and DOT5.1 are glycol based and hygroscopic*...they need to be periodically changed as the moisture they absorb lowers their BP. To answer Volvorama's question/idea, I have seen the Master Cylinder of a modern vehicle have a custom shaped membrane under the cap which served as a flexible separation of the fluid surface and (moisture containing) make-up air above...it was able to to get sucked down as fluid level dropped with pad wear...I thought that was pretty slick... I'd recommend against silica gel for possible contamination reasons, besides...even if you figured out how to hold a little desiccant packet above the fluid level to keep it dry, I expect it [desiccant] would get wet from sloshing fluid (contaminating it [fluid]!), besides, it would soon be ineffective, because it is essentially exposed to outside air by way of the vent hole, [so you would essentially have left the desiccant packet in the open where it would absorb the (unlimited) moisture available from the air, and soon be ineffective and only ballast!] and desiccant packs have a limited moisture capturing capability!

SwAm; Glycol fluid discolors as it absorbs moisture...good practice with glycol fluids  is / [I like] to flush each corner while bleeding until clear new fluid comes through. Good explanation/correction of Maxiboy's oversimplification. Regarding 3 years shelf life for an unopened product!!! ...that product manager must be HIGH!...but he's just regurgitating the corporate line...and they want to sell product...in today's world, 5 years is forever! ...that is laughable in view of the longevity of our vintage Volvos!...just one more reason to go to silicon IMO, see below!

DOT5 is Silicon based and non-hygroscopic...I have converted all my systems (hyd. Clutches also) to it with superior results! I like and recommend it! See: http://sw-em.com/Amazoning%20with%20...ke%20Fluid.htm
Volvorama; Our tests [...and in our group of acquaintances, we had some very astute engineers, including consulting a materials engineer!] showed only minimal swelling (data sheet states 2-3% expected [per materials data sheet]), and easily >5 times seal service-life increase, and decreased metal part corrosion (big plus!)...and it's STABLE and doesn't need changing...so once a decade is good!  Search Brickboard.com for DOT5 silicon fluid , and you should find lots of info by George Downs (now deceased, RIP!) Materials Engineer and former military man who got much practical experience with Brake fluids while stationed in Panama supporting vehicular operations (where humidity is 700% on a dry day...and you grow mushrooms in your armpits if not careful!). He was a huge advocate of DOT5!

Cheers

* ...as a demonstration of the height of bureaucratic stupidity, the DOT designated the next development of glycol fluid 5.1, suggesting to any sane and logically thinking human that it is a development of Silicon based DOT5...which it most certainly IS NOT! Do not mix DOT 5.1 and DOT5!!!

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Some Comments of mine to a thread asking about DOT5 conversion:

Poster:  "Why?" [...clearly a founding member of the MoFWC (Men of Few Words Club)!]

My response: 

"Biggest advantages: No internal corrosion, no change/decrease in brake function when recommissioning a car stored over the winter (or longer), fivefold increase in brake component service life and fluid change (since there is no degradation in fluid in terms of moisture content or Boiling Point) and component replacement interval (and components which get removed/replaced look a hell of a lot better than those of DOT4/5.1 PolyGlycolEther filled systems!). Minor  advantages [some, for instance smokers, who don't have such a steady hand, might call this major]: No damage to paint if spilled on it. Disadvantages: Cost. Easily micro-aerates possibly causing a soft pedal, so needs special handling to prevent this (NO SHAKING!). Racers found out it is more compressible at elevated temps than PGE fluids, so NOT SUITABLE for racing.

I've collected all I've found relevant on the subject here: https://www.sw-em.com/Amazoning%20with%20Silicon%20Brake... Practical experience with multiple vintage care owners and caregivers: Nothing but positive!

...bottom line: For all my vintage vehicles, which spend much of their time waiting for me to take them on the road, I love it, and highly recommend it!"

Another response (the reader can pretty much figure out the comments my response was to):  

"I agree with your first point, that Boiling Point does not decrease as it does with hygroscopic fluids, as they absorb moisture, but not the second point, (of damaging rubber components). Silicon is the best thing for EDPM (synth) rubber! Besides...you don't think it would have been given a DOT rating, qualification approval to use in vehicles if it was not compatible do you?  Don't get me wrong...I don't think the DOT bureaucrats are that smart at all (we can have a discussion about for instance, non-standard bumper heights, and Headlight illumination pattern standards elsewhere!), but I have ZERO respect for the those DOT IDIOTS, who mis-classified PolyGlycolEther as DOT5.1!" 

...and yet another response of mine...:

"I'm with you!...but I wouldn't call it "contamination" of the rubber parts so much, if system was filled with a PGE non-silicon, but nonetheless approved DOT fluid, because seals are compatible with BOTH fluids (so I'm certain there is no compatibility issue)...it's just that the two fluids don't play nice with each other, so the emulsion/jello/gummi-snot it might turn into will probably not work so well hydraulically, and that is rather important here...(I HAVE experienced first hand, a wheel-cylinder bound up by this snot in an inadequately flushed system also!) ...so I guess when changing over a system, flush, flush, and flush again is the word, but when starting with a newly renovated system, I'd disassemble/clean and reassemble everything with silicon lube like D-C 200 (See: https://www.sw-em.com/Product%20Reviews.htm... ) and go with DOT5 fluid (and I have and I do!) every time, with excellent long-term results (most recently, this includes the ease of disassembly of Calipers rebuilt 25 years ago, car parked the last 10, and condition I found rubbers and pistons in, see: https://www.sw-em.com/Girling%203%20Piston%20Brake...)." 

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Frame capture from Swedespeed Forum (by highly experienced and respected George Downs, †):

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Frame capture from another vintage car Forum, where the thread was actually about hydraulic brake light switch compatibility with DOT5 fluid: 

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Info from surfing:

http://home.wanadoo.nl/this-is-me-at/brembo/brembo.html 

From: Chicagoland MG Club techtips [

http://www.chicagolandmgclub.com/techtips/525.html

Silicone Brake Fluid: Snake Oil, It's Not

There have been many views put forth about this product, but two are inescapable: it must work as brake fluid or it never would have received DOT 5 approval, and, it physically cannot absorb moisture. This latter point was confirmed in a test performed by two members of the Society of Automotive Engineers, with the results published in SAE Paper #780661. [No luck on Search for this...yet!] They reported "After two years of service and 56,295 miles, the physical properties of the (silicone brake) fluid were unchanged, and the water content was 0.00%. System wear and corrosion were non-existent."

More:  http://www.chicagolandmgclub.com/techtips/525b.html

The Real Story:
Conventional vs. Silicone Brake Fluid

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Additional notes (from email):

Bmustnilh@XXXXXXXX wrote:

On your tech article on DOT 5--- I've been trying to find out if DOT 5 is lighter or heavier than water. If lighter there is another big problem. 

Water will still condense in the reservoir with temp and air pressure changes such as the cycling of engine compartment temp. Will such condensation float on top of the DOT 5 or will it drop to the bottom of the reservoir and be distributed through the system defeating the main purpose of DOT 5. 

Please forward to the tech writer.

 My Response:

Bmust;

Thanks for your input...you clearly have an excellent point. Depending on relative densities, if any condensed water were to sink to the bottom, it would certainly get pumped throughout the system and its components and there goes any advantage!

...so I put on my tech writers hat, went out to the garage, and put a couple of drops of water into a small cup of DOT5 fluid...they promptly FLOATED, so I think were OK. 

BTW, as I recall from flushing out DOT4 fluid systems (I like to pump a full reservoir worth through each corner)...with the price of DOT5 fluid being what it is, I typically store the full (glass) drain/bleed bottle on a shelf for a year or so in which time the DOT4 and DOT5 fluids separate out perfectly (DOT5 on top). This allows me to pour the silicon fluid off the top and use it again (for flushing ONLY)...naturally the final reservoir fill is done with fresh fluid.

...any other thoughts, don't hesitate!

Regards, Ron
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from Brickboard regarding reassembling split calipers:

Jim McDonald wrote: 

> No sweat; I've done it several times. 
> The only problem is that the o-rings between the halves (you'll see 
> the grooves) aren't available as replacement parts; you'll have to get 
> them from a bearing supply house. The recommended compound for brake 
> fluid is EPR, [Ref:  https://en.wikipedia.org/wiki/Ethylene_propylene_rubber ]not neoprene or Viton. 
> Instead of worrying about the torque, use a dab of blue Loctite and 
> tighten the bolts good and tight. Otherwise, look for a torque spec 
> for a similar sized bolt (and still use Loctite). The rest of the 
> assembly procedure is pretty straight forward, but I recommend 
> stainless pistons, from John Farrell Auto Parts. The 122 calipers are 
> the same as 1800S (and XKE 4.2 liter). 
http://www.fortunecity.com/silverstone/tread/1046/

Jim;

I have some split calipers that I've been holding on to...I haven't needed them yet, but have thought about what I would do if I ever needed to put them back into service. Sealing between the two halves is clearly the critical issue...if compatible o-rings are available, that's great (and thanks for the info), but I was thinking that an alternate solution would be to counterbore one of the caliper halves for an interference fit copper squish washer which would certainly compatible with ANY brake fluid. 

Thanks also for the info on Stainless pistons...they can't be cheap!...but I love that stuff!!!

Cheers

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One of the best compilation of fluid characteristics comparison I've run across:

Copied from:  http://www.vtr.org/maintain/brake-fluids.html

DOT3

DOT3 brake fluid is the "conventional" brake fluid used in most vehicles. One of the most familiar brands is "Prestone."

Advantages:

• DOT3 fluid is inexpensive, and available at most gas stations, department stores, and any auto parts store.

Disadvantages:

• DOT3 will damage natural rubber brake seals and should not be used in any car suspected of having natural rubber seals (most Triumphs prior to 1968) [Girling Systems, therefore possibly also valid for Vintage Volvo.]
• DOT3 fluid eats paint!
• DOT3 fluid absorbs water very readily. (This is often referred to as being hydroscopic.) As such, once a container of DOT3 has been opened, it should not be stored for periods much longer than a week before use.
• Since DOT3 fluid absorbs water, any moisture absorbed by the fluid can encourage corrosion in the brake lines and cylinders.

DOT4

DOT4 brake fluid is the brake fluid suggested for use in late model Triumphs. The most familiar brand is "Castrol GT-LMA"

Advantages:

• DOT4 fluid is available at most auto parts stores, and at some (but not all) gas stations or department stores.
• DOT4 fluid does not absorb water as readily as DOT3 fluid.
• DOT4 fluid has a higher boiling point than DOT3 fluid, making it more suitable for high performance applications where the brake systems are expected to get hot.

Disadvantages:

• DOT4 fluid eats paint! Small leaks around the master cylinder will eventually dissolve away the paint on your bodywork in the general vicinity of the leak, and then give rust a chance to attack the body of your car!
• DOT4 fluid is generally about 50% more expensive than DOT3 fluid.
• Since DOT4 fluid still absorbs some water, any moisture absorbed by the fluid can encourage corrosion in the brake lines and cylinders.

DOT5

DOT5 brake fluid is also known as "silicone" brake fluid.

Advantages:

• DOT5 doesn't eat paint.
• DOT5 does not absorb water and may be useful where water absorption is a problem.
• DOT5 is compatible with all rubber formulations. (See more on this under disadvantages, below.)

Disadvantages:

• DOT5 does NOT mix with DOT3 or DOT4. Most reported problems with DOT5 are probably due to some degree of mixing with other fluid types. The best way to convert to DOT5 is to totally rebuild the hydraulic system.
• Reports of DOT5 causing premature failure of rubber brake parts were more common with early DOT5 formulations. This is thought to be due to improper addition of swelling agents and has been fixed in recent formulations.  [I'm still seeking details on this...Ron].
• Since DOT5 does not absorb water, any moisture in the hydraulic system will "puddle" in one place. This can cause localized corrosion in the hydraulics.
• Careful bleeding is required to get all of the air out of the system. Small bubbles can form in the fluid that will form large bubbles over time. It may be necessary to do a series of bleeds.
• DOT5 is slightly compressible (giving a very slightly soft pedal), and has a lower boiling point than DOT4.
• DOT5 is about twice as expensive as DOT4 fluid. It is also difficult to find, generally only available at selected auto parts stores.

DOT5.1

DOT5.1 is a relatively new brake fluid that is causing no end of confusion amongst mechanics. The DOT could avoid a lot of confusion by giving this new fluid a different designation. The 5.1 designation could lead one to believe that it's a modification of silicone-based DOT 5 brake fluid. Calling it 4.1 or 6 might have been more appropriate since it's a glycol-based fluid like the DOT 3 and 4 types, not silicone-based like DOT 5 fluid. (In fact, Spectro is marketing a similar new fluid which they are calling Supreme DOT 4, which seems less confusing   [Good for them...an (from all appearances...or until I see a reasonable explanation) idiot maneuver doesn't deserve to be perpetuated!  Because of this improper nomenclature, someone might quite reasonable (but wrongly) add DOT5.1 fluid to a reservoir full of DOT5.]

As far as the basic behavior of 5.1 fluids, they are much like "high performance" DOT4 fluids, rather than traditional DOT5 brake fluids.

Advantages:

• DOT5.1 provides superior performance over the other brake fluids discussed here. It has a higher boiling point, either dry or wet, than DOT 3 or 4. In fact, its dry boiling point (about 275 degrees C) is almost as high as racing fluid (about 300 degrees C) and 5.1's wet boiling point (about 175 to 200 degrees C) is naturally much higher than racing's (about 145 C).
• DOT5.1 is said to be compatible with all rubber formulations.

Disadvantages:

• DOT5.1 fluids (and Spectro's Supreme DOT4) are non-silicone fluids and will absorb water.
• DOT5.1 fluids, like DOT3 & DOT4 will eat paint.
• DOT 5.1 fluids are difficult to find for sale, typically at very few auto parts stores, mostly limited to "speed shops."
• DOT 5.1 will be more expensive than DOT3 or DOT4, and more difficult to find.

General Recommendations:

1. If you have a brake system that doesn't leak or show any other signs of failure, but has old seals in it, don't change fluid types as a result of reading this article. If it isn't broken, don't "fix" it -- you may simply break it instead!
2. Flushing of the brake system every couple years to remove any absorbed or collected water is probably a good idea to prevent corrosion, regardless of the type of brake fluid used.
3. DOT3 is dangerous to use in Triumphs with natural rubber seals, and thus should not be used in such cars, except as a temporary "quick fix to get me home" solution. (If this is used as a "get-me-home" solution, bleed the system as soon as possible, and be prepared to replace all your seals.)
4. DOT3 is an adequate brake fluid for use in later Triumphs, although it is rarely preferred. My recommendation would be to simply not use it.
5. DOT4 fluid, for a slight increase in cost, will give significantly increased resistance to moisture absorption, thus decreasing the likelihood of corrosion compared to DOT3.
6. DOT4 fluid has a higher boiling point than DOT3, making it preferable for high performance uses such as racing, autocross, or excessive use of the brakes in mountainous areas. For even greater braking performance, consider going to DOT5.1 or a high-performance version of DOT4 fluid.
7. DOT5 is a good choice for the weekend driver/show car. It doesn't absorb water and it doesn't eat paint. One caveat is that because it doesn't absorb water, water that gets in the system will tend to collect at low points. In this scenario, it would actually be promoting corrosion!
8. DOT5 is probably not the thing to use in your race car although it is rated to stand up to the heat generated during racing conditions. The reason for this recommendation is the difficult bleeding mentioned above.
9. When changing from one fluid type to another, as a minimum, bleed all of the old fluid out of the system completely. For best results, all the seals in the system should be replaced.
10. As always, your experiences may vary.  [obvious CYA...is the guy who wrote this a lawyer?]

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[From www.Brickboard.com]... posted by Ron Kwas on Tue, May 6th 2003 at 9:23 AM ...in response to "Opinions on DOT 5.1? [120-130]" posted by JohnMc  on Mon, May 5th 2003 at 11:42 AM 

Link to Thread:  http://www.brickboard.com/RWD/index.htm?id=628286

John;

First I'll state that I have no first hand experience with this fluid, so all I can do is just opine on what I know...and that's what you did ask for!

DOT 5.1 does seem to be a good solution if you just want to replace the fluid and don't want to otherwise open up the system...the makers have addressed the most important issues (compatibility with polyglycolether fluids, moisture neutralization, seal compatibility is naturally paramount and so presumed)....it would seem to be an upgrade in both temperature performance and long term corrosion because of the moisture neutralizing characteristics, and doable by just replacing and bleeding since its fully compatible with the old fluid. So far so good.

The blanket statement of "10 years" bothers me a bit though...I would expect the fluid moisture neutralizing mechanism to to be limited to some finite amount (its typically some compound which will grab and bind-up any water molecules, keeping them from doing the same to ferrous components of the system), and they do not state what happens after that mechanism gets saturated and used up (moisture separation, and the accompanying BP decrease etc.)...the point is that "10 years" is probably the sales department talking of the bestcase (Arizona?) where very little moisture is absorbed. So it would seem that the fluid still needs periodic, scheduled replacement.

So it would seem to be some improvement over the fluids which had no moisture absorbing mechanism, but I would love to hear from someone about the longterm performance (without replacement, and in a slightly more typical moisture environment - like New England, or the rainy pacific NW). The question I have which I guess I would love to see an answer to is: What increases the hydraulic system life so much when silicon fluid is used in comparison to polyglycolether fluids...is it the non moisture absorbing characteristic, or the fluid/seal combination itself...I guess now we can find out...as soon as someone has the fluid in a system for longer that 5 or 6 years...

Cheers
 

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External sources attributed.  Otherwise this information is Copyright © Ronald Kwas.   The terms Volvo, and Girling are used for reference only.  I have no affiliation with either of these companies than to try to keep their products working for me, help other enthusiasts do the same, and also present my highly opinionated results [like for instance, that the US-DOT exhibited the height of idiocy for their inconsistent nomenclature application in designations of the DOT5 (silicon) and DOT5.1(non-silicon)].  The information presented comes from my own experience and carefully considered opinion, and can be used (or not!), or ridiculed and laughed at, or worshipped, at the readers discretion.  Don't muck around with brakes if you don't know what you're doing!  As with any recipe, your results may vary, and you are, and will always be, in charge of your own knuckles, and future!

You are welcome to use the information here in good health, and for your own non-commercial purposes, but if you reprint or otherwise republish this article, you must give credit to the author or link back to the SwEm site as the source.  If you don’t, you’re just a lazy, scum sucking plagiarist, and the Boston Globe wants you!  As always, if you can supply corrections, or additional objective information or experience, I will always consider it, and consider working it into the next revision of this article...along with likely the odd metaphor, or analogy (see:  ABS!) and probably wise-a** comment.