Anyone know the difference between Dot 3 and Dot 4 brake fluid?
Brake fluid
#1
Posted 17 April 2014 - 06:39 AM
#2 _hutch_
Posted 17 April 2014 - 06:44 AM
#3 _Bomber Watson_
Posted 17 April 2014 - 09:37 AM
3, 4, and 5.1 are not.
Difference between 3 and 4 is boiling point.
Cheers.
#4
Posted 17 April 2014 - 09:52 AM
Difference between 3 and 4 is boiling point.
Cheers.
Viscosity is also different. DOT 3 is better for older cars which don't need the higher boiling point, because it's slightly thicker, resulting in less leaks.
Dr Terry
#5 _Bomber Watson_
Posted 17 April 2014 - 09:57 AM
#6 _outer control_
Posted 17 April 2014 - 10:16 AM
which fluid is best for high boiling point as i have heard some brands are better?
#7 _Bomber Watson_
Posted 17 April 2014 - 11:25 AM
#8 _judgelj_
Posted 17 April 2014 - 05:49 PM
didnt know about the dot 3 being thicker = less leaks. wonder if it will remedy weeping M/C.
#9
Posted 17 April 2014 - 07:23 PM
Some vehicle manufacturers do not recommend using DOT 4 in systems that were designed for DOT 3. The DOT 4 fluid can damage the rubber components in DOT 3 systems.
This Penrite tech article explains the problem with some DOT 4 brake fluid in DOT 3 systems.
87 Dot 3, Dot 4 and Super Dot 4 Brake Fluid
From time to time the question of the use of DOT 4 and Super DOT 4 brake fluids in the systems of vehicles initially calling in the handbook for a DOT 3 fluid arises. One manufacturer in particular is very firm in their insistence on a DOT 3 type being used.
The first thing one normally thinks of in terms of brake fluids is the boiling point. There is a general acceptance that "the higher, the better" and therefore, from this viewpoint Super DOT 4 is better than DOT 4 which, in turn is better than DOT 3. Indeed the difference between the three specifications is in terms of the boiling point.
Another important area of brake fluid performance is the effect the fluid has on various types of rubber. In this testing the increase in diameter of a rubber cup, the softening of that cup and the degree to which the cup swells when in contact with the brake fluid are all evaluated. Interestingly, all three fluid types, DOT 3, DOT 4 and Super DOT 4, have exactly the same specification in terms of their effect on rubber. Despite this, it seems that it is because of an adverse effect on rubber that manufacturers have been so insistent on the use of DOT 3 fluids in certain systems.
At first glance this appears quite illogical, the specifications all the same, but manufacturers insisting on one type. But a closer look at the specifications shows that it is not entirely without logic. Specifications by their very nature allow a certain range of results, e.g. in the rubber testing referred to above the specification is met provided the swelling of the cup is between 1% and 16% (and the increase in diameter and softening have specifications just as wide). So that a brake fluid formulation can pass the specification at, say, 15% swell and potentially act quite differently in a particular brake system to a fluid which meets the specification at, say, 3% swell.
Penrite believes that those manufacturers who are so adamant about the use of DOT 3 have had bad experiences somewhere in the world with DOT 4 and/or Super DOT 4 fluids which differed markedly from traditional DOT 3 fluids in terms of their effect on rubber even though those fluids still met the specification claimed. The illogical part was for these manufacturers to immediately brand aN DOT 4 and Super DOT 4 fluids as "bad".
Penrite maintains that a carefully formulated DOT 4 or Super DOT 4 will not produce these adverse effects on rubber. Testing of our Super DOT 4 formulation produces results in terms of the affect on rubber which are practically indistinguishable from those of DOT 3. Penrite has marketed DOT 4 fluid since 1996, changing to Super DOT 4 in 2000. In that time we have never had a problem in any brake system in any make of vehicle. Penrite stands behind its products - we have no hesitation in continuing to recommend our fluid in all brake systems calling for Super DOT 4, DOT 4 or DOT 3.
Andrew Poole
Technical and Production Director
Penrite Oil Company Pty Ltd
http://www.stoptech....ers/brake-fluid
A seldom talked about characteristic is that because of this chemistry, the DOT 4 fluid will have a more stable and higher boiling point during the early portion of its life, but ironically once the fluid does actually begin to absorb water its boiling point will typically fall off more rapidly than a typical DOT 3.
Edited by ls2lxhatch, 17 April 2014 - 07:26 PM.
#10 _Bomber Watson_
Posted 17 April 2014 - 07:27 PM
That explains Toyota.
Was always perplexed by them, untill now.
Even my 05 Hilux specifies DOT3.
Cheers.
#11
Posted 17 April 2014 - 07:27 PM
Can we start again ?
Dot 3 is originally an older fluid suitable for drum braked cars and clutch systems
Dot 4 was the next progression of fluid when they went to disc brakes and most of the time has a slightly higher boiling point
Dot 5.1 was the next progression and was designed for higher performance disc braked cars and cars with ABS
Dot 5 is silicone and should not be used in any performance application and despite not absorbing water (hygroscopic) does still allow corrosion to form in the system as the water stays as 'droplets' and still rusts things.
Dot 3,4,5.1 are glycol based and DOT 5 is silicone based
Toyota specifies a particular Dot3 fluid for their vehicles with ABS as its actually lower in viscosity and more suitable for ABS valving systems.
DOT ratings don't have much to do with temp ratings anymore. So check the label and buy whats suitable for your application
But generally a good DOT4 is best suited for higher temps. But is not a cure for overheating the brake system
And if your master cylinder is weeping... fix it... changing the fluid will do nothing to fix it
#12
Posted 17 April 2014 - 07:39 PM
As SOL once said, "oils aint oils"
#13
Posted 17 April 2014 - 08:59 PM
Nissan specifies DOT 3 for the Z32 which has ABS and discs all round.
#14
Posted 17 April 2014 - 09:18 PM
Some become addicted to drinking the Dot 2 but claim they can stop anytime..... <tish> <boom>
#15 _Bomber Watson_
Posted 17 April 2014 - 09:23 PM
Can you even get dot 2 mainstream anymore or is it all underground?
Someone i know craves some dot 2.......
#16
Posted 17 April 2014 - 09:59 PM
#17 _Bomber Watson_
Posted 17 April 2014 - 10:08 PM
Win!!!
Random history lesson from the zen master, if we may, something that has always made me curious, did a DOT1 and DOT2 exist, and why were they superseded?
Cheers.
#18
Posted 17 April 2014 - 10:44 PM
Early ones were caster oil based and had very little temp ability
http://en.wikipedia....iki/Brake_fluid
#19 _Bomber Watson_
Posted 17 April 2014 - 10:59 PM
Interesting.
As is this:
" All approved fluids must colorless or amber to be acceptable for street use in the U.S."
So the blue shit we get here would not be legal in the US?
Total tangent here.
Cheers.
Edited by Bomber Watson, 17 April 2014 - 10:59 PM.
#20
Posted 18 April 2014 - 09:36 AM
Interesting.
As is this:
" All approved fluids must colorless or amber to be acceptable for street use in the U.S."
So the blue shit we get here would not be legal in the US?
Total tangent here.
Cheers.
That makes sense. The biggest enemy of brake fluid is moisture ingress, as the fluid ages & increases in moisture content is goes darker. Therefore it is easier to see this if the fluid is clear. The blue & green fluids we see in Australia are legal here (AFAIK), but the Yanks have rules about them, it appears.
This bring up a very important point about brake fluid. Most keen car guys, change their engine oil religiously, fuss over their radiator coolant, but many never give a 2nd thought about the car's brake fluid. In fact it is just as important as the other 2 fluids, even more so in cars with ABS.
Dr Terry
#21
Posted 18 April 2014 - 11:48 AM
Well Dr Terry,
Look's like it is time to change the Brake Fluid Today. Dave I
Brake Friday
#22
Posted 18 April 2014 - 12:27 PM
Once brake fluid get to 2% water content its temp rating can half
So brakes should be flushed every 2 years... clutches every year
#23
Posted 18 April 2014 - 12:44 PM
There are a few methods that can be used to test the water content in brake fluid.
The common methods are covered in this article.
http://www.bendix.co...ctions-issue-13
However brake fluid is cheap and if you have a vacuum bleeder then flushing the fluid is a reasonably simple task. I did it last week whilst replacing the discs and pads on my Z32.
#24
Posted 18 April 2014 - 01:00 PM
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