Synthetic brake fluid

[Ray Greene]

Hello Gents, I recently read all the former posts on using silicon vs Dot 3 or 4 brake fluid, and saw that synthetic fluid was now on the market. Has anybody used it yet and have any recomendations? I just worry about leaving the regular brake fluid standing in the car over the long winters here in the Northeast.
Ray

 

[Dave Russell]

I think that all modern brake fluids, with the exception of silicone, are synthetic. Synthetic is just a marketing ploy to sell something new. Can anyone prove differently?

The non silicone fluids are purposely made to absorb water. Otherwise the water would just accumulate in globs & cause rust & corrosion. Absorbing the water allows less water concentration in any given location. Better a little water throughout the system than a lot collecting in a few places like wheel cylinders.
D

[ 02-11-2004: Message edited by: Dave Russell ]</p>

 

[RF Thom]

I have utilized synthetic brake fluid in my Healey, MG, and when my daily runner had a brake line rust through after the repair I purged the system and installed synthetic. It's priced higher than petrolium based products, but not as high as silicone fluid, not sure if it is a market ploy, but it's abiliy to not absorb moisture is the reason I used it. I've also used silicone fluid in the past and had a problem with compatability with some of the cylinder rubbers. As a side note synthetic fluid will damage paint just as the petrolium based products do.

Regards, Bob

 

[ThomP]

I use both synthetic and silicone fluid. It depends upon which car. The A30 has synthetic fluid. I routinley change the fluid in all of the cars. As the brake systems need rebuilding, I will move to entirely silicone, because it does not affect the paint.

Funny language; english. If I mix alcohol and water together I have synthesized a compound. Therefore I could call the mixture "synthetic"

I read in "Practical Classics" that the staff "routinely" mixes silicone fluid with the earlier glycol product, because "one of the requirements of newer brake fluids is that they be compatible with earlier products"! I'm not recommending this, I was surprised they put this in their magazine, because I have read the contrary in every other publication

I beleive that traditional brake fluid is ethelyne glycol based, not petroleum based. In fact, petroleum based products are the biggest cause of failure of brake components.

 

[w. scott brunkhurst]

I used silicone fluid and had one of the master cyl's refuse to come back to full return. Put Casterol DOT4 back in and had no problems.

SB

 

[Steven]

The only approved hydraulic fluid for British brake systems is Castrol. The owners manual for the TR6, and the Bentley manual specify this very clearly. That makes the decision on what to use easy for me. If you're worried about lines rusting through you can always bleed your system once every couple of years.

 

[PC]

I would disagree that a mixture of alcohol and water is a "synthetic compound". It is not a compound. It is a solution.

In a solution the atoms or molecules are mixed together but do not combine into more complex substances. They just sort of swim around together. To create a compound you have to link atoms or simple molecules together to form more complex molecules. Synthetic just means some person did it.

Nature has given us lots of useful complex compounds like crude oil, peanut oil, honey and milk. We massage them around, even break them up but nature did the hard part. Somewhere along the way chemists figured out how to do motor oil better than decaying algae and rocks do it. Peanuts, bees and cows are still smarter than we are.

Similarly chemists have figured out how to make glycol type brake fluids that have some improved characteristics over those that are extracted from natural sources.

Whether any of them are better for you or not depends on your application.


PC.

 

[ThomP]

PC

You're right, my choice of examples was not the best, but my point about the english language and marketing spin are still valid. I have actually synthesized a solution (allbeit a simple solution) therefore it is synthetic.

SB

Your profile lists two early LBCs. Did this problem occur on the Silverstone or MGA? If so, have you read the article in the May 2003 Healey Marque by Roger Moment about Silicone fluid and early Lucas/Girling master cylinders?

As he says "While you may not agree with my diagnosis or fix, I do beleive that what I learned may be of help to others...."

 

[John Loftus]

<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Dave Russell:

The non silicone fluids are purposely made to absorb water. Otherwise the water would just accumulate in globs & cause rust & corrosion. Absorbing the water allows less water concentration in any given location. Better a little water throughout the system than a lot collecting in a few places like wheel cylinders.
D
<hr></blockquote>

o.k. humor me a little bit. My take on this is different..

I don't think Glycol based brake fluid is purposely made to absorb water ... it's hydroscopic nature is just one of it's properties and not a good property. If you fill a jar of Dot 3 to the rim and leave it out for awhile it will overflow because it is absorbing water from the atmosphere (o.k. I haven't tried this myself but if anyone wants to play mr. wizard, let us know if it is true or not). Silicone fluid is not hydroscopic and will not overflow (another job for mr. wizard!). The glycol based fluids will absorb moisture from the air, through the brake lines (unless they are teflon lined), through the master cylinder seals, etc. Dot 5 will not be pulling moisture from these sources so you shouldn't have a problem with much moisture getting into the brake system unless you get water into the system by accident (such as spraying water into the reservoir). I have heard that the Silicone brake fluid was designed first for military vehicles which can be in storage for years without maintenance but must be able to perform immediately when required. If globs of water, rust and corrosion was a problem I don't think they would still be using it for 15+ years. Do you?

Cheers,
John

 

[w. scott brunkhurst]

TP

That problem was on an AH 3000.

SB

 

[Dave Russell]

<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by John Loftus:

o.k. humor me a little bit. My take on this is different..

I have heard that the Silicone brake fluid was designed first for military vehicles which can be in storage for years without maintenance but must be able to perform immediately when required. If globs of water, rust and corrosion was a problem I don't think they would still be using it for 15+ years. Do you?
Cheers,
John<hr></blockquote>

Hi John,
I was 'humoring you" a bit.

My statement was slightly "tongue in cheek" but is somewhat backed up. See this link;
https://www.xs11.com/tips/maintenance/maint1.shtml

Note the statement about Dot 4 absorbing a maximum of 3% water & the corrosion inhibitors handling it.

Also note the part about the US Army considering going back to Dot 3-4.

I suspect that the pro-con discussions will go on forever.
Cheers,
D

 

[Dave Russell]

John,
I think that we can find data to support almost any position on the brake fluid issue. There are recomendations to change fluid when the moisture content is more than 3%. However, the same amount of moisture does not have the same effect on all fluids.

For DOT 3-4 fluids the ERBP (equilibrium reflux boiling point) change is specd at 3 degrees. This is an indicator of boiling point vs moisture. The actual wet boiling points are different however.

My experience with brake fluids is neutral. No strong opinion either way. I have a 1984 Ranger, bought new, now with 115,000 miles on it. The brakes have never been touched, except for inspection, it still has the 20 year old original fluid & causes no trouble. Brake fluid has never been one of my worries. Maybe being in a dry climate helps.

The race machinery is taken apart often enough to assure frequent fluid replacement.
D

 

[John Loftus]

Dave,

I'm actually on the fence with the fluid issue and will need to make a decision soon. When I purchased my BJ7 it already had been converted to Silicone fluid so I've stayed with it and it's been problem free. I did go through the wheel, master and clutch slave cylinders early on and found some mild corrosion but no idea how long it had been there. Since I'm doing the full monty restoration right now with new brake lines and everything it would be the perfect time to switch back if desired. I'm going to try your 'brake fluid on paint' experiment with the paint system I'm using to see how the paint holds up. I bet the newer paint systems hold up better than the lacquers and enamels of the old days.

Cheers,
John

p.s. you need a 'tongue in cheek' Graemlin to let us now when you are kidding. 20 yr. old brake fluid. You had me going there!

 

[Dave Russell]

<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by John Loftus:
Dave,
p.s. you need a 'tongue in cheek' Graemlin to let us now when you are kidding. 20 yr. old brake fluid. You had me going there!

<hr></blockquote>
No Graemlin's. Dead serious, not joking. The fluid has never been changed, only topped up once in a while with DOT 3 to compensate for pad & lining wear. The fluid is kind of black but it has caused no problems. Same thing with a couple of other vehicles but they only have 10 years on the fluid. In fact I had never even heard of changing fluid until a few years ago. Race cars excepted. It must be some new problem or a solution in search of a problem.
D

 

[John Loftus]

<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Dave Russell:

No Graemlin's. Dead serious, not joking. D<hr></blockquote>

I know. Just pulling your leg. It's so hard to joke around sometimes without being face to face. Sorry about that. I'm sure there are many vehicles out there that never get the fluids changed but somehow they keep going and going. Some people don't even think they need to change the engine oil. My Saab mechanic has a few pictures on his website showing one result. https://www.swedecar.com/service_center.htm

John

[ 02-13-2004: Message edited by: John Loftus ]</p>

 

[Dave Russell]

John,
The same truck also has the original coolant in it. Only topped up a very little bit. Original hoses are in good shape. Belts have been replaced & oil gets changed about once a year. If it's not the climate, maybe it's the water or air?

Now the Healey is another thing altogether. Frequent replacement of all fluids & grease in many places. Plus the underside is self lubricating.
D

 

[spritenut]

"The only approved hydraulic fluid for British brake systems is Castrol. The owners manual for the TR6, and the Bentley manual specify this very clearly."

Could it be that silicone fluid was not around when these manuals were printed?
My Bugeye Sprite manuals don't mention radial tires either, so should I go back to bias plys?
Maybe I should go back to straight 30wt motor oil too. Maybe get rid of my seatbelts, halogen headlamps, and synthetic gear oil.
This debate will go on forever, there will be pros and cons. I use silicone, I have not found any cons yet in the 3 cars that are now using silicone fluid.

 

[CDK]

There seems to be a lot of focus on the aspect of water in the brake fluid.I belive you could use water as brake fluid if you did not use the brakes hard enough to heat the fluid to the boiling point.One of the primary concerns of brake fluid is just that, the boiling point of the given type of fluid used and the compressibility of the fluid\gas.Under perfect conditions you want the same presure created by the same amount of force each time.Because there are so many variables and little to no reference for us to judge this data, everytime we use the brakes, unless they go to the floor, they seem to work fine.For all practical purposes they do and under the driving conditions most of us use them we never notice a difference.Water in the system will cause rust the same as it causes rust anywhere else and would be considered normal wear.Silicone has poor repetetable compressibillity(I bet I did not spell either of those words right)and that is why it is not recommended for daily use.
CDK

 

[John Loftus]

<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Dave Russell:

I suspect that the pro-con discussions will go on forever.
Cheers,
D<hr></blockquote>

Hi Dave,

Thanks for the article. I really don't mind the discussion going on, each time a topic like this comes up I hear a new tidbit of info. I did find an article from Knott brake company that says after several years of service its not uncommon to find brake fluid with 7 to 8% water content in Dot 3 and 4 systems. https://www.knottbrake.com/tech_papers/brake_fluid_basics.pdf
So I'm not so convinced about the 3% figure.

John

 

[w. scott brunkhurst]

I auto-crossed a VW Rabbit for many years. Then I went to a track day
at Pocono Raceway. After several hot laps I found my foot going
to the floor as I braked for the infield hairpin. As I flew into the weeds
I realized what fade and fresh brake fluid were all about.

SB