exophthalmos

going to have my 15k service done on my 04' c4s. a reputable indy shop recommended a brake flush as well. how important is it, and what is it for? sorry im not a mechanical guy!

john

smackboy1

For regular street driving the recommendation is to flush the brake fluid every 2 years. Brake fluid is hygroscopic which means it absorbs moisture from the air. Moisture (and other contaminants) in the brake fluid lowers its boiling point. If the brake fluid boils from the heat generated by the brakes, the resulting gas, being compressible, will not transmit force to the calipers which will result in no brakes. No brakes = bad.

salayc

The moisture content in brake fluid can easily be measured. Replace it when it's out of spec.

Steven C.

Don't change it and have seal problems in the system for many a year in the future

exophthalmos

how do you measure that?

aaahhhh, that makes so much sense ! thank you.

Tippy

In my 14 years of driving I never thought changing the fluid was all that important, until I lost my pedal in my 911 when trying to stop at nearly 120 MPH at the drag strip. After I stopped the car and was about to turn onto the return lane, my pedal went to the floor. Freaked out, I tried it again and it got a little better, then by about 4 more times of mashing it, it had fully resumed. I was stumped on why the clutch worked but not the brakes for about 30 seconds (there on the same resovoir).

I talked to my Father about it and he goes, "you boiled the fluid in the calipers". I was like, Duh. Why didn't that dawn on me? The fluid boiled causing compressable (is this a word?) gases which made the brake pedal go to the floor but not the clutch. After speaking to my friend who owned the car for about 3 years, he said he had never changed the fluid out.

So, to the question, I would highly recommend changing the fluid. Moisture builds inside the system. Not only can it cause pedal loss, moisture can cause a whole host of other issues like corrosion.

Sorry for the long rant.......

exophthalmos

I guess how often should we change it??

Patrick

For street use, once every other year should be plenty. If you car sees any performance driving, such as track use, at LEAST once a year.

joes c4 cab

you can change it yourself pretty easy, but if you are not a mechanical guy, just bite the bullet and have it done.

ArneeA

Once a year is good!

More than once a year if you do alot of canyon/track duty.

Meister Fahrer

Corrosion due to moisture in the fluid can also affect ABS sensors, then you've got a panic stop and no ABS.... plus a bigger repair bill to replace them.

smackboy1

2 other quick points:

Whether you DIY or use a mechanic, when the brake fluid is flushed, make sure the clutch line is flushed out too. The clutch and brakes share the same reservoir and fluid. The clutch bleeder valve is high up on the transmission on the drivers (left) side and is a PITA to get to.

If the car will see any track time or you just want to be able to tell chicks at cocktail parties that you are using racing brake fluid, try upgrading to a brake fluid with a higher boiling point like ATE Super Blue Racing Brake Fluid DOT4.

Steven C.

I own 2 track cars and would NEVER go racing without flushing the brake system each time before I go out for the weekend. Some weekends on tight twisty tracks I flush it once over the weekend. Just not worth the risk.

salayc

A moisture meter is inserted into the reservoir. It's a pretty common shop tool.

smankow

just a few quick points. there is a difference between bleeding and flushing the system. Flushing is replacing the fluid where bleeding is letting out a little to check/remove air bubbles.

During track weekends, I'll bleed the system at the end of the day. If you're using quality fluid, there is NO REASON to change it over the weekend unless you are experiencing braking issues. If that's the case, you should reconsider the brake fluid that you're using.

Now, back to the original post. I believe that Porsche recommends replacing the fluid every 2 years. Their fluid is quite good. I'd be hesitant to use Super Blue in a non-track car as it has a tendency to stain the tank and lead a future buyer to believe that the car was tracked. I had a dealer replace my fluid once (before my first event). My wallet was lighter by around $125. I quickly bought a pressure bleeder and now it's a DIY.

So, if you're not a mechanical guy, have the dealer or repair shop change the fluid. Better to be expensive but done correctly than save $$ and have problems.


Steve