Recent Topics
Questions about Castrol TWS / Edge Professional
by bimmerdriver
07/24/14 09:38 PM
Pennzoil HM 5w20 in new car
by wemay
07/24/14 09:27 PM
Recalls & more recalls. Cars are now too complex!
by antiqueshell
07/24/14 09:23 PM
Honda MM logic vs. BITOG logic
by Pajamarama
07/24/14 09:07 PM
Alignment done on my ranger
by Blkstanger
07/24/14 08:47 PM
MMO suggestions!
by lawman1909
07/24/14 08:38 PM
2003 Ford Escape Air bag code 47
by Bluestream
07/24/14 08:23 PM
MP3 Download
by ryansride2017
07/24/14 08:19 PM
"15 Awful Convertibles"
by GumbyJarvis
07/24/14 07:45 PM
Electric Clutch Repair
by GreeCguy
07/24/14 07:05 PM
station wagon vs small suv
by PeterGreen
07/24/14 06:48 PM
'08 Ford V10
by rrounds
07/24/14 06:26 PM
Newest Members
chancelee, XJSteve, joehupp, BwanaBob, gt40p
50744 Registered Users
Who's Online
92 registered (123Saab, Alltherage, 2010_FX4, abycat, Alex38, ABCarr, 9 invisible), 1724 Guests and 224 Spiders online.
Key: Admin, Global Mod, Mod
Forum Stats
50744 Members
64 Forums
216749 Topics
3411582 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: 14040
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.
_________________________
I told a chemistry joke....there was no reaction. smile

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


Registered: 12/05/09
Posts: 10976
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: 416
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
'07 Altima
'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: 1714
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
_________________________
"Capitalism is the extraordinary belief that the nastiest of men for the nastiest of motives will somehow work for the benefit of all" J. M. Keynes

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


Registered: 06/05/02
Posts: 14040
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.
_________________________
I told a chemistry joke....there was no reaction. 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: 62
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: 3953
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: 14040
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)
_________________________
I told a chemistry joke....there was no reaction. smile

Top
Page 2 of 2 < 1 2