This is equal parts brake fluid and water shaken (not stirred). Based on what I've read in the archives this should mean DOT 5 brake fluid. Confirmations would be appreciated.

Thanks,
Bruce

 

Sure looks to be DOT 5. Assuming it came out of your master cylinder?

Another test might be to put it on something painted (that you do not want!). DOT 3/4 should attack the paint. DOT 5 will not.

You could also add some DOT 3/4 fluid to that jar, and see if it mixes with the water (it should). In other words, the DOT 5 would stay on the top and stay the same vol., and the water / DOT 3/4 would grow in vol. and become a colored mix.

Plasticman

 

Looks like Dot 5 to me.

 

Some dot 3/4 brake fluid will not attack paint.

 

Yup, that's DOT5 - no question about it.

 

Out of curosity what are the benefits of DOT 5 over DOT 3 and 4? I have DOT 4 in my 67 Coupe right now. Would it be wise to flush my system this winter and use DOT 5 (I'll be installing a rebuilt master cylinder)?
Roy

 

Roy,

Probably best to do a search on DOT 5 (or Silicone brake fluid).

Just a brief answer: DOT 3/4 is a different chemical than DOT 5 that is related to anti-freeze (glycol esters and ethers). It absorbs moisture (hygroscopic), and therefore will corrode your brake system from the inside out. Moisture is absorbed through the flexible rubber hoses and through the master cylinder cap diaphram. Most (if not all) DOT 3/4 fluids will also attack your vehicle's paint. DOT 3/4 "should be" flushed out a minimum of every 2 years (contrary to what the vehicle manufacturers say - by their ommision of any service requirement). Also as a note: All DOT 3/4 fluids are "synthetic"!

DOT 5 is Silicone brake fluid that does not absorb moisture, but it is "thicker" in viscoity and therefore never should be used in an ABS equiped vehicle. The US Army switched to DOT 5 in 1982 due to it's decrease in maintenance characteristics, and it's consistent viscosity in extreme temperatures. But those systems were designed with DOT 5 in mind. It is also 2 times more compressible than DOT 3/4 fluid (but that is only an issue in vehicles that are on the ragged edge of performance - such as race vehicles). It does not need replacement (one of my vehicles has the same fluid in it since 1986 and it still looks like new fluid). It also will not attack paint. However, it is harder to bleed due to it's affinity to trap air bubbles (pour slowly and never start to bleed until all bubbles have dissapated, and never shake the container!).

There is a newer DOT 5.1 that is a poly glycol formulation (not Silicone), and I have no real knowledge or usage of it.

Also DOT 2 is essentially castor oil (and should not be used), even if you could find it.

Plasticman

 

willowdog, here is another test that you might want to try. But this time I would try adding an olive.

DOT brake fluid is "hydrophilic". This means the fluid will absorb water from the air. Rumor has it that you can fill a shot glass with DOT fluid and after an hour or so the glass will overflow. The DOT brake fluid absorbing moisture from the surrounding air causes the volume increase. This is why every container of DOT fluid requests that you keep it closed when not in use. As the fluid absorbs water its vaporization temperature (or boiling point) is reduced. DOT 4 becomes no better than DOT 3 and eventually degrades in performance to the level of DOT 2. Amazingly enough, a small amount of moisture will be absorbed right through rubber seals and nylon hydraulic lines (virtually any material except metal or glass). This is why car manufacturers recommend brake fluid replacement every two to three years.

 

Regarding the colors of various brake fluids:

The problem is that while DOTs 2, 3, and 4 are all compatible with each other, none are compatible with DOT 5. If you add DOT 5 to a system that already contains 2, 3 or 4, the resulting mixture will dissolve the rubber 0-rings common to all hydraulic systems. Within a couple of hours the brake system will leak like a sieve, and the fix requires a complete system overhaul with all new rubber parts. Not cheap, or easy. The moral of this story so far: Don't ever mix DOT 5 (known to most as "the blue stuff") with any other DOT fluids (which are all the color of motor oil).

 

Plasticman, I did some research regarding DOT 5.1. Apparently it is a higher temperature rated version of DOT 4. It is totally not compatible with Dot 5........ I am sure a lot of people will think it is an improvement of DOT 5, and will end up mixing non compatible fluids.

 

Just a flushing will not be good enough. You really need to be doing this when either replacing all your calipers or rebuilding them with new rubber. All rubber hoses should also be changed including your master cylinder either be changed or rebuilt at the same time when deciding to go with Dot 5. I have Dot 5 brake fluid in my C-3 but still have Dot 3 in my C-2 as Dot 3 was in the 67' when I purchased it almost 5 years ago. Both cars have SS Sleeved calipers. Actually you really don't need Dot 5 with the use of SS Sleeved calipers since Dot 3 or Dot 4 shouldn't corrode the SS Sleeves as it did the previous cast cylinders that came from the factory.

As someone already mentioned on this forum bleeding a Dot 5 system is harder to do especially when doing it manually but I found when doing this with the Motive Power Bleeder either fluid was a breeze to bleed.

 

If DOT 5 has a blue tint to it, why is everyone saying the fluid in the picture is DOT 5. The stuff in the picture is the color of motor oil. I'm going through the same thing right now. I pulled some fluid out of my master cylinder and put it in a clear tube and let it set. After some time it separated and now looks like willowdogs except in mine the clear milky fluid is on top and the brake fluid is on the bottom. I assumed it is DOT 3 or 4.

 

DOT 5 came in both a light yellow/clear color and a purple tinted color. I have samples of both. Do not use color as a criteria for determining DOT 5 fluid. See my comments on Willowdogs other fluid thread.

All the silicone fluids I have seen are lighter than water, but I have seen reports (unsubstantiated at best) of a silicone fluid that is heavier than water. I cannot verify this and would not bet a dime that this is correct. However, I have to mention it "just in case".

Best method is to try adding some DOT 3/4 fluid to the mix (after carefull measurment of the vol. of your existing fluids) and see which liquid increases in vol. If the "water" grows in vol., then whatever you have in your system is not DOT 3/4. May be silicone and then again it may be something "else".

If I was to bet on what you have, it would be DOT 3/4 that just separated. DOT 5 should not mix with water at all, and should separate almost immediately.

Plasticman