What is this stuff? Found in the master cylinder reservoir in my new (to me) 993 when attempting to do a brake fluid flush.

 

Merry Christmas.

I can only imagine that someone has put in a very wrong fluid at some point in the past, and it's reacted with actual brake fluid.

Flush, flush, and flush some more.

Do you have a C2, or a C4/Turbo?

 

C2. And boy did I flush! And the line still clogged when I tried a pressure bleed, so I had to pressurize backwards from bleed valve to MC reservoir. That did the trick and after cleaning out the reservoir fully several more times, I was finally able to properly bleed and flush all four.

 

On occasion while bleeding the brakes I find a bit of wax like buildup coming out of the bleed valves. Looks just like that. I’ve also seen a few waxy particles floating around the brake fluid reservoir. I run with RBF, and bleed the brakes regularly.

 

Yes, it was kind of waxy, but also crumbly. I’m just glad I got it cleared out. Timely flushes for this car from here on out!

 

I use RBF600 or 660, and I've never seen anything like that.

 

Brake fluid is hydroscopic, and will soak up any moisture in the air. Absorbed water can eventually form into that waxy crud. Worn seals or bleed valves can exacerbate the problem.

 

This Thread dates back twenty years describing this issue in 993’s. I switched to a vented cap in my 964 m, and have never seen any residue in that car.

 

Bleed the clutch and post a pic of the black sludge that comes out of that!

We also need some photos of your new to you 993.

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Yeah, i’ve been thinking about the clutch slave and the unreachable back compartment in the reservoir. Gonna talk to my mechanic after the holidays before attempting that.

 

Here you go.

https://rennlist.com/forums/993-foru...eed-setup.html

 

adding another project to the to do list!

 

Nice car. Congrats on that.

The clutch slave is pretty simple to bleed. Once you know how to do it, it can be done in a minute (assuming you have a lift).

The hard part is figuring out where the bleeder valve is (it's further up and diagonal from where I logically thought it should be). And then once you spot it, you need to figure out how to position your hand in a way to reach the bleeder valve and not dumping the black sludge all over your face while bleeding.

Search for @Foxman 's post on it. That's how I learned.

It shares the same brake fluid and master cyclinder as your brakes - so unfortunately you're not done bleeding yet...

Good luck.

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Here’s my thread on the Remote clutch slave bleed

Absolutely worth doing Andreas’s remote clutch slave setup. I had this in my 964. They yanked it out when rebuilding the engine last summer. I replaced it, but it got yanked again when I swapped out the MPL clutch salve and went back to the original stock slave. I don’t recommend the MPL clutch slave. Too soft, and they can leak.

 

I flush and bleed the brakes on my C2 every 3 or 4 years and have not seen this kind of debris. My car is a daily driver, so that it may keep the wax precipitate in solution.