Mystery Green Brake Fluid..

[Kevin C]

I bought the Audi about nine months ago and one maintenance item I hadn't gotten to was flushing the brake fluid. I was pretty surprised when it came out dirty pond water murky green. DOT regulations don't allow for green dye in brake fluid, and it definitely was brake fluid. 32 oz of new fluid, it was still coming out colored! I also noticed a few tiny dark flecks in the old fluid.

The second round is this afternoon.

Searching the internet, there are a lot of reports of people bleeding fluid and having it come out green, but no o sources of green fluid ( at least in the US).

Strange, and I'm glad I finally got around to it. The interesting thing is the brakes all look pretty fresh and all the pad and rotors are OEM. Its looks like all service was done at the dealership.

I'm going to run another large can (32 oz) through and call it a day. This has to be the most brake fluid I have ever had to run through a car to get to clear at the bleeder screws.

Anyone else have green brake fluid?

[old guy]

Green like this?

I have encountered this in some VW factory fills. Possible used occasionally in Audi's?

[Kevin C]

More like those...

As I the new fluid purged through, it went from murky brownish green, to more of a bright green.

It looks like it was supposed to be green, or it was mixed with algae from a very still pond.

[old guy]

I suspect yours came with the bright green fluid as in the pic I posted and this is the first time it has ever been changed.

Wow........

[mauromj]

Interesting. Isn't Pentosin power steering fluid green?...

[old guy]

Interesting. Isn't Pentosin power steering fluid green?...

Yep.

[Kevin C]

This was the color after I ran 32 oz of clear brake fluid!

It took two full containers to get rid of the green tinge.

In all I used three large bottles of fluid!


I picked up a Harbor Freight vacuum bleeder. the tool itself is great The ungreat part is vacuum bleeding sucks. Air leaking around your bleeder screws makes the process really slow. My wife / brake bleeding assistant is away on a business trip... So I tried the one person bleeding method.

It works great if you can get a good seal at the bleeder screw threads. Some one man bleeder screws have a check valve and Vibra-Tite on the the threads. The Vibra- Tite stays a bit gummy and helps. My local parts store doesn't stock it.

What worked really well was stacking a couple of O rings on the bleeder. The air leak went down to nothing... Much faster.



32 OZ into the bleedfest....



No clue what the green fluid is... Or if it degraded and turned that color. For now at least it's gone.

[Kevin C]

It turns green over time.

That was what I was thinking... That and the fluid change was about 11 years overdue.

I couldn't see the true condition until taking them apart and inspecting the caliper bore and pistons. Rust, corrosion, scoring, and dirt.

That's my concern... The upside is the bleeder screw tip (sealed side) didn't have any corrosion. The gunk I did get during the flush was sludge, not rust residue.

Put anti-sieze on the bleeder screw threads (after cleaning them) so that they seal better, turn easier, and don't seize up. Same for brake lines.
I'm reluctant to install non-original bleeders. Supposedly the tolerances don't always match, and the conical sealing surface isn't mated to the caliper from repeated use, similar to brake-bedding

The anti seize on the fittings trick is a great tip. I was doing it when I lived on the east coast and any part that didn't get some loctite or anti sieze would get corrosion welded in place. Using the doubled up O rings also worked quite well, better than including Vibra-Tite that is used on some quick bleed screws. Once the two O rings make firm contact, the air leak around the threads disappears completely. One of the bleeders on my rear calipers was a bit looser than the rest; that was what worked. It was nice to see the stream in the tube go fro almost all air, to almost all fluid.

http://www.harborfreight.com/automot...der-92924.html

Kit I picked up....

https://www.vibra-tite.com/products/...-3-threadmate/

Material you can apply to your existing bleeders (or a new set) to seal the threads.

Update: The brakes feel great with fresh fluid! Kind of like a mini brake upgrade.... One more thing off the to do list. UCA are next...

[diuvic]

I'm guilty of never flushing my brake fluid. Mine also looks green. I can take pictures later if you'd like.

I will do a lot of work on my car when I get off these restrictions. I can't bend over or pick heavy objects since I slightly injured my back.


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[DiertyEuroSpec]

Brake fluid is recommended to be changed every two years as is it hydrophillic and absorbs water. When water/condensation gets in the lines its no beauno.

[Kevin C]

Brake fluid is recommended to be changed every two years as is it hydrophilic and absorbs water. When water/condensation gets in the lines its no beauno.

That change is cheap insurance from losing expensive brake components to corrosion. That's why I was surprised, the car had extensive service records and was always dealer serviced. I would have thought, that at some point the dealer would have flushed the brake fluid.

Seems great now... And now that I have my fancy new Harbor Freight vacuum bleeder, doing the other cars will be less of a hassle.

[SJorge3442]

I had a brake line explode on a Buick century in a parking lot. All due to rotted brake lines. Went to start the car, stepped on the brake, and kaboom. Sounded like a .22 handgun, followed by fluid splashing. Now, I change my fluid regularly.

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[seanf86]

mine was also green when I changed the fluid in my 02 when I bought it, maybe the Audi fluid turns green when it absorbs moisture.

[diuvic]

Haha! That's what I get for helping someone move. That human hoist thing is amazing.


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[Kevin C]

It turns out, the brake fluid was changed in 2007, at 40,000 miles.


I just checked the service records on my car.

it looks likes the fluid was about 9 years old.



Snip from 2003... My car was quite the lemon when it was new! Steering wheel, airbag, speakers, door trim, glove box, tail light, instrument cluster and, fuel sender all done in the first few years.

https://www.audiusa.com/content/dam/...-Year-2004.pdf

[Kevin C]

A quick update... I did some reading and learned that as brake fluid ages from heat exposure the additives that balance the PH get depleted. Once the PH is out of range, any copper in the system is susceptible to corrosion. This is not a moisture problem its a PH problem. Where is the copper? On brazed steel tubing it's in the braze joint and coats the ID of the tubing. On copper nickel tubing... It's what the tubing is made of. The bad part is as the copper in the brake fluid is missing an electron. I'm not sure why, or who took it but from what I read it's missing.

The missing electron makes the copper in solution want to react with any iron in the system.

Short story... the green color is dissolved copper and an very strong indicator that your brake fluid is bad and may be damaging your brake system.

[GTA]

Short story... the green color is dissolved copper and an very strong indicator that your brake fluid is bad and may be damaging your brake system.

Wow. It's a good thing I flushed out my system this weekend. And here I assumed that the green brake fluid in my system was what Audi used.

I bought the car nearly 4 years ago and this is the first time I'd flushed out the system as everyone mentions that it's a good preventative maintenance measure.

I used Prestone Dot4 Synthetic fluid. Since it's my daily driver, I hope that it won't be a problem in our cars because I'm seeing differing opinions on what fluid to use.

[hightime80]

I used the same fluid as well! Its all they had at autozone. Stops on a dime. Will report back if it causes a hole in my hydralic system lol.

[diagnosticator]

Audi brake service instructions specify using only a pressure bleeder to bleed the brakes or change the brake fluid. Using a pressure bleeder avoids all the hassles from using a vacuum bleeder at the calipers. Using a vacuum to bleed the brakes can cause problems bleeding brakes when vacuum pressure expands the air bubbles, possibly blocking the brake fluid from moving properly in the system during bleeding. A pressure bleeder compresses the air bubbles to a much smaller size and pressure bleeding is a lot more effective purging contaminated fluid with no chance of introducing more air into the system.

A couple of years ago, all Ate Blue brake fluid was recalled from the US market since federal law does not allow colored brake fluid. The only color allowed is natural colored brake fluid.

[GTA]

A couple of years ago, all Ate Blue brake fluid was recalled from the US market since federal law does not allow colored brake fluid. The only color allowed is natural colored brake fluid.

Thanks for the update. So now all brake fluid is the same color, and green is a no-no. Going forward, you can't alternate colors when flushing out the system and the only way to tell if you're actually flushing out the old stuff is to gauge how much goes into the reservoir.

Good to know.

[Kevin C]

FYI, despite not being called out as the preferred method to bleed the brakes, the vacuum bleeder worked great. What matters is did it do the job? It sure did and at a very affordable price. It even made short work of bleeding a new clutch slave cylinder.

As a mechanical engineer with a background in automotive I would not hesitate to recommend this method as long as you make sure you get a good seal at the bleeder screw.

[hightime80]

When I bled my brakes I had my old lady pump the pedal and I worked the bleeder at the caliper. Archaic? Yes. Did it work? Yes. Did it bust a seal in the master cylinder like everyone said it would? No😝

[diagnosticator]

FYI, despite not being called out as the preferred method to bleed the brakes, the vacuum bleeder worked great. What matters is did it do the job? It sure did and at a very affordable price. It even made short work of bleeding a new clutch slave cylinder.

As a mechanical engineer with a background in automotive I would not hesitate to recommend this method as long as you make sure you get a good seal at the bleeder screw.

Not everyone has the practical and theoretical insights you have, or are able to know when something is wrong. No offense intended. I was not responding to your post anyway, just stating facts.

[CyberPMG]

Good info for everyone to see. To avoid having the brake fluid end up like this, follow this simple rule: All DOT 4 brake fluid must be flushed completely every 2 years regardless of miles.

If you don't know, then you either need to find out or get it done so you know for sure. It's for your own safety (and those around you).

[Kevin C]

Not everyone has the practical and theoretical insights you have, or are able to know when something is wrong. No offense intended. I was not responding to your post anyway, just stating facts.

Not a problem. FYI, I recognize that a pressure flushing tool is the best way to go... Just wanted to make sure that there is no confusions that there that other methods that technically are not as good (but still good enough to get the job done) will get you there and for short money. As CyberPMG stated, the important thing is to make sure it gets flushed.

[Kevin C]

Update. I should have posted this last year. When I did my B7 brake upgrade I pulled apart my old calipers to check for corrosion. Despite the green brake fluid that appeared to be super old the bores were clean and looked quite good for their age. I still plan on changing the fluid at least every two years.

[EuroxS4]

Could be from moisture in the brake fluid supporting algae growth. But copper corrosion sounds about right. All brake fluids are hygroscopic and should be changed/flushed every 2 years.

[turtleman]

When I did my brake fluid swap, on my A4 which the previous owner neglected the fluid was green as well. I had no corrosion despite the fluid being an almost emerald green, I still have the fluid in the make shift receptacle.