[PeterVV]

Diffusion, l have difficulty believing it would be possible for the new fluid in the master cylinder to travel through brake lines and hoses with an internal diameter of maybe 1/16” and make it all the way through the lines, through the abs unit, through to the calipers ,from one side of the caliper to the other side of the caliper ( front) or all the way to the rear caliper, maybe 4 meters of brake line and back to the master cylinder to exchange new for old fluid. Yeah, right.

Agree 100%. No question changing the fluid in the master cylinder only is better than nothing, but I don't believe for a second that most of the moisture and contaminants present by the wheel cylinder furthest away from the master cylinder are at all likely to make it back to the master cylinder, even over a long period of time.

 

[jzwu]

It is amazing how magical fluid can be. Believe me!

Next time before you drive, notice the fluid level in the brake fluid reservoir. After a hot run meaning you use the brakes a few times during the drive and look at the fluid level again.

I bet you will see the level changes, usually increases. That means the brake fluid has traveled throughout the system.

 

[flash gordon]

It is amazing how magical fluid can be. Believe me!

Next time before you drive, notice the fluid level in the brake fluid reservoir. After a hot run meaning you use the brakes a few times during the drive and look at the fluid level again.

I bet you will see the level changes, usually increases. That means the brake fluid has traveled throughout the system.

Expansion, after driving on a hot day, is normal for any type of fluid, but it does not mean the brake fluid has circulated the brake system.

 

[jzwu]

Diffusion comes after expansion since all fluid is connected in the system.

 

[PeterVV]

I happened to be at our local indy in the past hour picking up one of our vehicles, and I asked the owner about the idea of just replacing the brake fluid in the master cylinder repeatedly versus bleeding at each wheel. This is a guy who is been a German car specialist for more than 25 years.

I mentioned the concept of diffusion, and his response was that by definition it tells you that you are never getting out all of the old bad brake fluid no matter how many times you change the fluid in your master cylinder only. So you are never achieving the desired result.

He mentioned in all his years of being in the business he has never heard of one professional nor one vehicle manufacturer that recommends replacing brake fluid in this manner, and he doesn't understand why anybody would resort to this given that the traditional method of bleeding at each cylinder is so easy and elementary.

To quote him "brakes are not a place for taking shortcuts".

Of course we are all free to do whatever we want to our vehicles, but it's certainly not a shortcut I am going to risk taking.

 

[NC TRACKRAT]

FWIW, I've been a HPDE instructor for over 35 years. Without fail, no further out than 3 days before an event, I will bleed my brake system with a MOTIVE Power Bleeder. I have never lost my brakes at an event. Porsche recommends bleeding the system every two years. As mentioned previously, this allows for the removal of moisture. Don't risk your life or others by not performing this simple, relatively inexpensive procedure.

 

[ttmacan]

FWIW, I've been a HPDE instructor for over 35 years. Without fail, no further out than 3 days before an event, I will bleed my brake system with a MOTIVE Power Bleeder. I have never lost my brakes at an event. Porsche recommends bleeding the system every two years. As mentioned previously, this allows for the removal of moisture. Don't risk your life or others by not performing this simple, relatively inexpensive procedure.

+1 on the motive power bleeder it’s so easy. I was dreading the brake fluid changes as well and then I got the power bleeder and the motive brake fluid catch cans. It’s such a breeze now and old fluid is caught in the cans so really makes the process a lot cleaner.

 

[767 CA]

HI...Im wondering why these cars need to have the brake fluids changed so often...never heard of this requirement in other modern cars and have never had it done in other newer cars that i have owned ....

 

[HazelPDX]

Just don’t do what I did by replacing OEM brake fluid with ATE 200 on my Macan. I figured what is good on my 987 is good on the Macan. Nope! Causes massive pedal squeak coming from master cylinder. Stick with OEM or Pentosin Super Dot 4.

 

[Her95B]

Just don’t do what I did by replacing OEM brake fluid with ATE 200 on my Macan. I figured what is good on my 987 is good on the Macan. Nope! Causes massive pedal squeak coming from master cylinder. Stick with OEM or Pentosin Super Dot 4.

I've used ATE 200 on Porsche cars for years, and years in the life of a Porsche tech means a lot of Porsche of all models and years and never experienced what you describe.
Something went wrong in there but I can guarantee you that it has nothing to do with the ATE 200.

 

[jzwu]

Just use good quality low viscosity brake fluid. It’s not rocket science.

 

[Yadkin]

HI...Im wondering why these cars need to have the brake fluids changed so often...never heard of this requirement in other modern cars and have never had it done in other newer cars that i have owned ....

DOT4 fluid absorbs water over time, and that causes steel parts to rust. A three year cycle is cheap preventative maintenance. Why don't many manufacturer's recommend this? Your guess is as good as mine.

A brake fluid tester is an inexpensive tool that reports percent water in the fluid. It takes ten seconds to sample the fluid in your master cylinder. If it's more than 1%, change out the fluid.

 

[jzwu]

Most cars use DOT 3 brake fluid, which is lower performance but also less prone to water absorbance.

 

[HazelPDX]

Just don’t do what I did by replacing OEM brake fluid with ATE 200 on my Macan. I figured what is good on my 987 is good on the Macan. Nope! Causes massive pedal squeak coming from master cylinder. Stick with OEM or Pentosin Super Dot 4.

I stand by my assertion (above) that ATE 200 in the Macan can (and does) cause massive brake squeak in the master cylinder, but the correct fluid is Porsche OEM or DOT 4 LV (not Super DOT 4 as I incorrectly stated above). Flushed out the ATE 200 with (Pentosin) low-viscosity (LV) and the squeak immediately went away. Now jumping ahead two years, tired of the squeaking clutch pedal on my 987, I flushed out the ATE 200 with LV and voila! - instant fix.
I'm certainly not asserting that all clutch and brake master cylinder squeaks are caused by the type of brake fluid, and I recognize that many Porsche owners have had no issues using ATE 200, but many have....including me. Just food for thought. It's worth a bit of google search before deciding to flush. FYI, Porsche genuine OE fluid is DOT4 LV.

 

[Her95B]

DOT4 fluid absorbs water over time, and that causes steel parts to rust. A three year cycle is cheap preventative maintenance. Why don't many manufacturer's recommend this? Your guess is as good as mine.

A brake fluid tester is an inexpensive tool that reports percent water in the fluid. It takes ten seconds to sample the fluid in your master cylinder. If it's more than 1%, change out the fluid.

Porsche includes the brake fluid replacement every two years,
I'll not trust the tool to extend the flush interval, as the brake fluid that suffer the most is the one on the calipers and not the fluid on the reservoir, sticking to the two year interval is the best way to guarantee performance and durability.

 

[oqjnLu@>@W]

I didn't see it mentioned in the posts above concerning brake fluid water absorption, so I am posting this note.

Recall that brake fluid will float on top of water if they're in the same system. With that in mind, please realize that
testing the brake fluid in your Macan's brake fluid reservoir will tell you NOTHING about the moisture (read: WATER)
present in the system at the calipers, the lowest level in the system and where water will accumulate first.

If you've heard of "frozen" caliper pistons these are caused by excessive moisture present at the calipers. Eventually
the water causes corrosion between the caliper pistons and their bore.

Another item to bear in mind is water has a much lower boiling point than brake fluid. Repeated heavy braking will result
in water compromised brake fluid boiling before it otherwise would. Once the brake fluid has reached that state the
driver recognizes it when the brake pedal travels all the way to the floor with little to no noticeable braking to the vehicle's
speed .


NOTE: DOT3 brake fluid typically has a lower boiling point than DOT4 brake fluid. It is considered lower performing.

 

[eminemupnorth]

I stand by my assertion (above) that ATE 200 in the Macan can (and does) cause massive brake squeak in the master cylinder, but the correct fluid is Porsche OEM or DOT 4 LV (not Super DOT 4 as I incorrectly stated above). Flushed out the ATE 200 with (Pentosin) low-viscosity (LV) and the squeak immediately went away. Now jumping ahead two years, tired of the squeaking clutch pedal on my 987, I flushed out the ATE 200 with LV and voila! - instant fix.
I'm certainly not asserting that all clutch and brake master cylinder squeaks are caused by the type of brake fluid, and I recognize that many Porsche owners have had no issues using ATE 200, but many have....including me. Just food for thought. It's worth a bit of google search before deciding to flush. FYI, Porsche genuine OE fluid is DOT4 LV.

I wish I had read this thread earlier. I flushed mine with ATE 200 and now have the brake pedal squeak. Started right away! Going to have to flush it out with ATE SL6 or Pentosin LV. Which one is better?

 

[HazelPDX]

I can't speak to SL6 but the Porsche spec is low-viscosity... so I stand by Pentosin LV or Porsche genuine. You'll need two liters to flush it well.

 

[Chinner]

I am currently using ATE SL6 without issue.

 

[muncie]

Flushed mine with ATE SL.6 too. It's DOT 4 low visc. Have used it on several cars needing low visc fluid