Recent Topics
Clearance oil at Advanced Auto
by SJohnson
09/16/14 12:19 PM
HUH?
by MolaKule
09/16/14 11:53 AM
'tis the season to buy snow tires.
by A_Harman
09/16/14 11:25 AM
Generator Quick Oil change
by henni
09/16/14 11:20 AM
OIl Specs API Class
by co1615
09/16/14 10:38 AM
2015 Honda DI and CVT issues?
by Falken
09/16/14 10:01 AM
Adding HD to my comp...
by daves66nova
09/16/14 08:14 AM
Big brothering by Discount Tires
by grampi
09/16/14 07:37 AM
Toyota 0w 20 in a 2014 Honda DI engine
by silverado1
09/16/14 07:26 AM
What do worn valve seals look like?
by Spetz
09/16/14 05:37 AM
4 Bean Soup
by Char Baby
09/16/14 05:24 AM
Whay diesel oil turns black immediately after chan
by DibroTeam
09/16/14 02:15 AM
Newest Members
dougout, CDot, mazarnelli, poiyt, VAzx6R
51314 Registered Users
Who's Online
99 registered (3800Series, 87sammy, Apollo14, abycat, 1999nick, 10 invisible), 1768 Guests and 222 Spiders online.
Key: Admin, Global Mod, Mod
Forum Stats
51314 Members
64 Forums
219306 Topics
3460738 Posts

Max Online: 2862 @ 07/07/14 03:10 PM
Donate to BITOG

Page 2 of 2 < 1 2
Topic Options
#3086379 - 08/05/13 10:35 AM Re: Chemistry of Brake Fluids [Re: Garak]
MolaKule Offline


Registered: 06/05/02
Posts: 14472
Loc: Midwest
Originally Posted By: Garak
Thanks for that. I, too, had heard such a thing mentioned. Of course, it's never something from a company that makes the stuff or in a sourced article. It's just mentioned in passing in some general tech article.


Exactly, inferential information from the Internet is dangerous.
_________________________
"It only knows that it needs, it does not know WHAT it needs." Spock from Star Trek smile

Top
#3087147 - 08/06/13 01:48 AM Re: Chemistry of Brake Fluids [Re: MolaKule]
Garak Offline


Registered: 12/05/09
Posts: 11302
Loc: Regina, Saskatchewan, Canada
I blame the German automakers. wink In North America, where everyone specifies DOT 3, few (if any) manufacturers call for a brake fluid replacement interval. The Germans, who tend to call for DOT 4, often do call for a replacement interval. Therefore, there must be something wrong with the DOT 4 fluid, rather than just a different take on maintenance, of course.
_________________________
Plain, simple Garak.

2008 Infiniti G37 coupe - Mobil Delvac 1 ESP 5w-40, Hastings LF113
1984 F-150 4.9L six - Quaker State GB 10w-30, Wix 51515

Top
#3087252 - 08/06/13 07:48 AM Re: Chemistry of Brake Fluids [Re: MolaKule]
tc1446 Offline


Registered: 12/10/10
Posts: 457
Loc: NC
Some brand name cans say "Dot 3/4". I read this as it can be used either way or mixed. right or wrong?
_________________________
'13 Accord EX-L
'00 Ford Ranger
'14 Can Am SE6 (traded '11 with 32K miles)

Top
#3087726 - 08/06/13 03:52 PM Re: Chemistry of Brake Fluids [Re: tc1446]
jrustles Online   content


Registered: 02/24/13
Posts: 1967
Loc: Ontario, Canada
Thanks for the article Molakule!

Originally Posted By: tc1446
Some brand name cans say "Dot 3/4". I read this as it can be used either way or mixed. right or wrong?


Probably, just like motor oils. I personally wouldn't mix exclusively separate chemistries. Mixing different ethers/blends could, as Mola pointed out, change the boiling point of the resultant fluid, and this is where one enters into unknown-spec territory. Compatability-wise, if you had to do it, you could. shrug
_________________________
"No matter how paranoid or conspiracy-minded you are, what the government is actually doing is worse than you imagine" W.Blum

Top
#3087920 - 08/06/13 06:43 PM Re: Chemistry of Brake Fluids [Re: tc1446]
MolaKule Offline


Registered: 06/05/02
Posts: 14472
Loc: Midwest
Originally Posted By: tc1446
Some brand name cans say "Dot 3/4". I read this as it can be used either way or mixed. right or wrong?


What the label is saying is that it is a DOT 4 fluid with a higher boiling point that can also be used in DOT 3 applications.

Again gentlemen and ladies, let us not compare brake fluid to motor oil or other fluids.

It is a very specialized hydraulic fluid and is hygroscopic which means it can absorb moisture, which means you need to change it every three years or less.

Let me stress again, Brake fluid is a SAFETY ITEM.
_________________________
"It only knows that it needs, it does not know WHAT it needs." Spock from Star Trek smile

Top
#3157913 - 10/16/13 04:35 PM Re: Chemistry of Brake Fluids [Re: Tay]
gpshumway Offline


Registered: 06/18/08
Posts: 410
Loc: Minneapolis, MN
Originally Posted By: Tay
i read that DOT 5.1 is much more hygroscopic then DOT 4 and DOT 4 more then DOT 3.

is there any truth to this?


Not necessarily more total absorption for DOT 4, but they tend to absorb moisture at a higher rate. German cars take DOT 4 fluid, but require replacement every 2 years (in general), Asian cars take DOT 3 fluid, but only require replacement every 3 years.

Stoptech has a good white paper on this:
http://www.stoptech.com/technical-support/technical-white-papers/brake-fluid

Originally Posted By: Stoptech
The real differentiating factor is that DOT 4 fluid should be changed more often than a DOT 3 fluid, because of the effects and rates of water absorption.
_________________________
2007 Subaru WRX
2011 Honda Civic EX

Top
#3162635 - 10/21/13 01:10 PM Re: Chemistry of Brake Fluids [Re: JHZR2]
miro Offline


Registered: 05/05/13
Posts: 64
Loc: the Netherlands
Thanks for the huge contribution in this forum.
I really like to read your articles. I like the way how you explain- with simple words expunging such complex area like modern fluid chemistry


Edited by miro (10/21/13 01:11 PM)

Top
#3352601 - 04/25/14 08:52 AM Re: Chemistry of Brake Fluids [Re: MolaKule]
Oldmoparguy1 Online   content


Registered: 01/21/05
Posts: 4012
Loc: Charlotte, NC
I've always wondered, why did the auto industry settle on glycol type brake fluid? The aircraft industry uses a petroleum based fluid, at least in my experience. Looks like ATF.

Wayne
_________________________
"A gun is like a parachute. If you need one, and don't have one, you'll probably never need one again!" unclepaddy

Top
#3353381 - 04/25/14 09:46 PM Re: Chemistry of Brake Fluids [Re: MolaKule]
MolaKule Offline


Registered: 06/05/02
Posts: 14472
Loc: Midwest
I think it was due to five things:

1. Brake fluid system pressure

2. brake line materials

3. seal materials

4. compressibility of comparative fluids

5. flammability and vapors


Edited by MolaKule (04/25/14 09:47 PM)
_________________________
"It only knows that it needs, it does not know WHAT it needs." Spock from Star Trek smile

Top
Page 2 of 2 < 1 2