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What brake fluid do I have in my car...

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Dougal

Dougal

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G'day Chaps,

Does anyone know how to tell what type of brake fluid i have in my car. I hear that the most important thing is not to mix "DOT 4" with "silicon" as it does something to the rubber components. My guess is that its "DOT 4" as its cheaper...but it could be anything.

The only way I can think of telling is to put some on some paint and see if it strips it.

Any ideas?
 
Hey Mate,

DOT 3, 4 and 5.1 are polyalkylene glycols and water absorbent (hygroscopic). They are amber in color and may be chemically mixed although some manufacturers including Daimler-Chrysler recommend that they not be mixed.

DOT 5 is a purple (violet) colored non-hygroscopic silicone brake fluid which should not be mixed with the others.

You can either flush the brake lines and start anew or check the color of the fluid and act accordingly.

I personally prefer a simple and inexpensive DOT 3 from a metal can even though it not only removes paint, but also will remove the color from leather shoes.

Also, don't buy brake fluid in bulk as it begins to absorb moisture once opened.
 
Castrol LMA is a good choice for all British cars, as it's kind to the seals.

In any case, if you flush the brake circuits every two (2) years, you can avoid most moisture related problems.
 
Hello,

here I found in the www on this site:https://www.se-r.net/brakes/fluid.html

DOT 3 is what Nissan recommends. It's the normal stuff available in the US.

DOT 4 is chemically compatible with DOT 3, but with a slightly higher boiling point.

DOT 5 is silicone based fluid*. NOT compatible with DOT 3 or DOT 4.

More info about DOT 5 fluid:

There are certain mods that are really "trick", but require so much work or cost so much that almost no one will do what it takes to exploit it properly. DOT 5 fluid is one of them.

DOT 5 fluid is silicone based*, rather than glycol based like DOT 3 & 4. Being silicone based, DOT 5 fluid won't absorb moisture, while DOT 3 & 4 does. What this means is that you have to completely clean out your brake system of any traces of the previous fluid as well as any moisture, otherwise you risk causing corrosion in the system. Brakes will continue to absorb moisture near all seals anyways, so you will need to bleed the brakes on a regular basis to remove the moisture.
Since it carries a DOT rating, it must be compatible with the other DOT brake fluids. Note that I said compatible, because it certainly doesn't mix with the other fluids. Another reason to flush the system completely of the old brake fluid.
DOT 5 fluid tends to be rather viscous. When adding it into the system, it's real easy to get air bubbles in it which don't want to come out. It's impossible to get your brakes bled properly if there is air entrained in the brake fluid. And additional viscosity may not work with ABS.
If you're getting the stock or B13 brakes to a temperature where you need a DOT 5 fluid, you're going to be seeing other failures in the braking system, like the rotors warping and cracking, pads burning up, and the pin boots melting (if you're lucky) or catching on fire.

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* There are actually two types of DOT 5 fluids. There is a SBBF (Silicone Based Brake Fluid) and an NSBF, or Non Silicone Based Fluid. DOT 5 NSBF's are not widely found, however, and are beginning to get more recognition as their popularity grows.

Bye Michel- who use TRW DOT 4
 
G'day Chaps,
Fluid thats left is amber, and going by the fact that DOT5 is more expensive I'm sure previous owner wold not have used it!

I must stop taking things apart though, summer down here is upon us already...

Cheers for you help.
 
There have been posts on this subject before, especially about the "rubber" components compatability to some types, apparantly some types will eat the rubber components if they are not designed to be compatible
 
I know it is just a sample size of one, but for what it is worth..... when I finished my rebuild almost 2 years ago, it came time to fill the brake system. New hard and flex lines, new seals in master cyl and all slave cyls. I chose DOT 5 silicone fluid. I had numerous leaks and seeps for about 2 months. Drove me nuts. I thought maybe I should have listened to the people who believe that you should only use "the right stuff", that being non silicone, etc. due to seals that won't swell properly. The leaks turned into seeps pretty fast, and then the seeps turned into nothing. I was so surprised I checked the brake fluid level before every time out. In the last year and a half my brakes have not leaked a drop and I still check the fluid any time the bonnet is up.
 
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