In the last several years we have seen green tinted DOT 3 brake fluid and we are wondering what the contaminate might be. We have seen it in 90’s and 02’s mostly in American made vehicles. I have been in the business since the early 70’s and never saw this in the older cars and am wondering if there has been a change to the chemical makeup of the brake fluid or if there is something in the rubber compounds that has changed that might cause the problem.
Mineral brake fluid which is used in European cars is dyed green when new. Do not use them in vehicles designed for glycol-based fluids or the rubber parts of the brake system will be damaged.
I should add that unless I missed something that most American vehicles use standard fluid and perhaps the corrosion of copper seals has added a green tint to some fluids.
Dave,
Thank you for your reply, I am aware of the mineral fluid used in a number of the German cars and am certain this fluid is not being used. I had thought of the copper O-rings used in some cars, but I have not seen them used in any American cars, unless they are used somewhere in the ABS system.
Someone has suggested water in the fluid, but I find that doubtful.
Kit
Perhaps the fluid started as blue and now looks green. There are blue brake fluids on the market. That’s the best I can come up with. However, you could try emailing a brake fluid company and see if they can offer some insight. The question is interesting.
What you’re seeing is the copper used in the brazing of brake components oxidizing as the brake fluid breaks down. One of the things that’s checked on todays ABS systems is the amount of copper oxides in the brake fluid. If the concentration of copper oxides goes unchecked, it can raise havoc with ABS pumps.
Tester
That’s interesting. The clutch hydraulics in my VW have a green tinge when I bleed them. They are using the same glycol-based fluid as the brakes (they share a common reservoir for the brake master and clutch master), and to my knowledge there aren’t any copper components in that part of the system.
I’m guessing it’s assembly lubricant. On my first bleed, the fluid was dark green. On the second bleed, it was much less green. The fluid was in there about the same amount of time, so it stands to reason that there’s less of it now than before, leading me to believe it’s a remnant from the assembly process.
geez i used a brake fluid that was recommned by the mechanic i purchase a can of ate blue dot 3 brake fluid does it mean i am using crappy fluid?
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Isn’t the blue brake fluid used to determine when all the old brake fluid is removed during bleeding? It seems to me that the green fluid may be a combination of blue fluid and old yellow fluid that could occur if all the old yellow stuff was not completely removed from the system during bleeding. On the other hand, if this green stuff is seen in a new car in which the brakes have never been bled, than I have no idea.
I have an 01 International 4700 and recently had a lot of break work done. A couple front calipers rotors pads and a flush. Then an ABS recall was found and addressed. A month after the original brake job was done I had to replace a 3rd passenger side steer caliperbecause it was sticking according to the dealership. I told them it has had a jerk then a pull on all of the(jerks to one side or the other then pull the other way) calipers Ive tried, remanufactured from a parts store and new from the dealer. So the latest caliper that went on when bleeding they found semi dark green brake fluid. They advised that it needed to be flushed. Ok. They had no idea what causes it. 2 days later I go to put on a new dealer purchased nonremanufactered caliper to try and remedy my pulling issue and out come a tinted green fluid!!! Its lighter than the sample they had given me though. I did have a master cylinder installed a year ago though and the post about the assembly lube as well as the 1 about copper being used caught my attention. Sorry for the extra looong post. I have the light and dark as well as unused dot3 fluid in glass containers for comparing.