Green Brake Fluid

I performed a brake flush on my new to me 04 C2 (40th Anniversary) in advance of an HPDE event. The fluid came out an extremely dark cloudy green, which is leading me to believe the fluid is original and close to 20 years old. Flushed with Castrol SRF until clear/amber at all 4 corners. On track the braking performance was� not impressive. Particularly for a Porsche. Brakes required a Herculean amount of force, lots of pedal travel and still unable to trigger ABS. Wasn�t a fade issue, as the first lap was no different than the last. Fairly confident there is no air in the lines, as I used a Motive power bleeder and saw no bubbles. Upon return home, the fluid color is now green again, but a light clear green, not the black green as before. My question is, if I did in fact perform the first brake flush this car has ever seen in 20 years, could components be damaged causing my weak braking performance? I plan to do another flush again to remove the green color, but my confidence in the system generally is waning. Should I start budgeting to replace the system (master, lines, ABS, booster, etc.) completely?

I also had a very green fluid, to the point where I wondered if the previous owner had mixed up the brake fluid reservoir and the steering fluid reservoir. You need to do a complete oil change, including engaging and draining the ABS pump, ideally with the Piwis. The Piwis procedure involves a traditional bleed of the 8 bleeders, then a new bleed with double activation of the ABS pump. If you have a manual transmission, you also need to drain and bleed the fluid at the clutch slave cylinder.

Yes! That was the color of my fluid exactly. Any idea how long your fluid was in for? Were you having any issues? If so, did the full bleed firm up the pedal? I�ll have to go to the dealer to get this done. I�m comfortable with a wrench, but not a Durametric/hacked PIWIS. And I hear the Durametric can�t do this procedure anyway.

The new low viscosity brake fluids are green out of the bottle. I'd think that is what was in both your cars.

There must be different colored fluids, even purple for Dot 5. I only knew the green LHM, which has no use for Porsche brakes. On the other hand, a fluid completely loaded with water turns green and can even attack copper pipes. If the braking is also terrible, it's not a new-generation green fluid, but rather a dead fluid.

Quotes source post: 20076060

I discovered this when I bought it second-hand. When I tested it, the braking was inconsistent, and like you, standing on the brakes, I did several pressure drains (2 b) and with the Piwis to be sure to clean and empty everything. I also discovered that my bleed screws were oxidized at the cone to the point of having to change them all. Do a complete bleed with the Piwis, specifying that the fluid was very old, and everything will be fine.

I�ve ordered some brake fluid test strips that will both identify the type of fluid (DOT 3, 4 or 5) and report the copper contamination. Will circle back whether the green fluid is the result of copper contamination or the DOT 5 green stuff.

Reporting back on test results. Old (dark green) fluid appears to be normal DOT 4 with extremely high corrosive levels (excess of 300ppm copper). Fluid in car now (light green) tests moderate corrosion (150ppm copper). Looks like this was just ancient fluid. Will flush again. Hopefully no permanent damage has been done.

Cool, that�s very interesting. Thank you for investigating and sharing your findings!

Quotes source post: 20075491

I would not replace anything unless you know for sure it�s faulty. Did anyone else, such as an instructor, drive it on the track as well? My first thought is that brake pads and the mating rotor surface have a pretty big impact on pedal pressure, initial bite, and how they behave after contended tracking sessions. And if the car wasn�t driven much or hard, the bite and grip might just not be there due to rust buildup that�s now embedded somewhat into the pad material. It might not be a bad idea to re-do the brake flush again, for 2 reasons: 1) You had a track event, and could have boiled some moisture somewhere in the system. 2) If you didn�t also bleed/replace the clutch/slave fluid, it could have impacted the brake system because they share the same reservoir. Certainly have a look at any hoses that might be suspect as well. You can probably test the brake booster to see if it�s not applying adequate assist in braking. People have done the GT3 master cylinder upgrade, but that�s an upgrade. A stock 996�s braking system is adequate for the occasional track day. If all else fails, consider the age and type of your brake pads and rotors. If they are old and worn, don�t go with drilled rotors, as the slotted rotors are better for tracking.

Quotes source post: 20090391

New pads (Ferodo DS2500) and rotors, properly bedded before event. I did not bleed the clutch, which along with the ABS system not being actuated likely accounts for the return of the green color after the flush. Performing another flush this weekend. Will test brake booster and vacuum. And SS brake lines will be the next step if I am still unsatisfied after the next flush. Having had the chance to poke around a bit on the forum, it seems like many other newcomers to the 996 are initially underwhelmed with the brake pedal feel. I may just be the latest example of expecting a more touchy/overboosted brake pedal feel common with other cars. The car does stop very well and no fade. It�s just a feeling of �wow I really need to mash this pedal and put it all the way to the floor� to get to the limit of ABS engagement. Far more pedal travel than I�m used to. But it does give far more control in brush braking. At the moment running Lime Rock, Watkins Glen will be the big test.

Great, you've confirmed everything. Now do things correctly and in the right order. Change your hoses if it's important to you, bleed the system simply so you can take your Porsche to a garage for a complete brake and clutch bleed with a PIWIS, and you'll have an optimal braking system.

There was blue high performance brake fluid that used to be available before being outlawed. There�s a good chance someone filled the system with that and didn�t fully flush out the older �goldish� stuff� This would give you �green� brake fluid�

Closing the loop on this. Another bleed fixed the issue. Pedal is now firm. Recap: if you see green brake fluid, it is ancient, filled with corroded copper, and you need to do multiple flushes to get it all out.

Quotes source post: 20092741

The Ate Blue that you refer to is simply Ate 200 without the blue dye. The blue dye was banned by the feds for an obscure reason, they did not like blue dye in brake fluid. Ate Blue stays blue; it does not turn green when used and abused. The Ate 200 is very good fluid. I used it for more than 30 years of racing. It never failed after many repeat high speed stops. It is still commonly available. It is about $20 per liter.

I confirmed with test strips that the green was in fact very high levels of copper contamination. Think Statue of Liberty. The fluid was very likely clear/amber when put in 20 something years ago. A negligent prior owner that never changed the fluid allowed the fluid to become waterlogged and this water corrodes copper in the brake lines and this leeches into the fluid, turning it green. This wet, contaminated fluid gives a spongy and soft brake pedal feel. A Motive power bleed of the brakes without opening the ABS and PSM modules resulted in the old contaminated fluid staying in the modules despite clear fluid coming out of the calipers. After some hard driving that activated the ABS and PSM, the old contaminated fluid retained in these modules was circulated back into the system turning my fluid green again (but a lighter more diluted shade) and still giving me a soft pedal. A second flush solved it. The clutch is allegedly also tied into the brake fluid reservoir and this also may have contributed to my issues in getting all the old fluid out.