Break Fluid

[hi8ha]

Can I mix ATE type 200 DOT 4 with ATE Gold type 200?

Also, does shelf break fluid expires?

[sburke719]

I believe they are compatible, but I'd recommend removing all of one and using only the other.

I have heard a two-year life for unopened cans of brake fluid on the shelf. Once opened, it begins absorbing moisture, which decreases the boiling point over time from the high "dry" boiling point toward the lower "wet" boiling point. How much and how fast largely depends on the ambient humidity where you are.

Recommendations - change fluid completely every year or two (more often if you're a track rat), using 2L of newly-bought good-quality brake fluid from unopened cans.

Edited March 31, 2014 by sburke719

[hi8ha]

Thanks

[jjb7]

DOT's 1 through 4 are compatible with each other. DOT 5 is NOT compatible with others. Porsche uses DOT 3 or 4. Use DOT 3 if this is just a street car. It will start off with a lower BP but it absorbs less water and last the longest. Use DOT 4 or racing spec if you're going to track the car to provide the most stopping power. The local track here forces brake fluid change once a year BTW.

[carrera3.2]

Actually, there is no chemical reason to think there is any finite "shelf life" for completely sealed, unopened containers of brake fluid any more than there is for unopened motor oil as long as there has been no exposure to elevated temperatures. The fluids are basically inert, long-chain polymers of ethylene glycol and related substances that won't react if there is nothng for them to react with in the container. However, if the container is opened to the atmosphere, these fluids are "hygroscopic", meaning they like to gobble up atmospheric water that, as stated above by sburke719, lowers their effective boiling point, something that you don't want to happen. Bottom line: originally sealed brake fluid, no problem with shelf storage; opened containers, don't save, but recycle the remainders at your local recycling center.

(Yes, I am a chemist by profession.)

[Ahsai]

For an opened container, I like to use a ziplock bag and push out the air to minimize the moisture.

I think ideally you could use one of those vacuum sealing machines for food that sucks up the air and seal the bag by melting the seams.

[carrera3.2]

I agree. The important thing is to keep out any additional moisture. The reason for annual or biannual changes of brake fluid in our cars is primarily because the reservoirs are generally open to the atmosphere and therefore the fluid picks up moisture from humid air. Of course, if you are tracking your car, the heating from the brake calipers will also degrade the chemical nature of the fluid over a fairly short time.

[hi8ha]

I just went with the ATE Brake Fluid - Gold.

[JFP in PA]

Can I mix ATE type 200 DOT 4 with ATE Gold type 200?

Also, does shelf break fluid expires?

ATE Gold and ATE Type 200 are the same product. Once opened, brake fluids in a partially filled original container have a shelf life of around 18 months to 2 years (an opened container will start to absorb moisture from the air in the container). To be safe, you can buy brake fluid test strips you can dip into stored fluid to check its moisture content before using.

[JFP in PA]

Actually, there is no chemical reason to think there is any finite "shelf life" for completely sealed, unopened containers of brake fluid any more than there is for unopened motor oil as long as there has been no exposure to elevated temperatures. The fluids are basically inert, long-chain polymers of ethylene glycol and related substances that won't react if there is nothng for them to react with in the container. However, if the container is opened to the atmosphere, these fluids are "hygroscopic", meaning they like to gobble up atmospheric water that, as stated above by sburke719, lowers their effective boiling point, something that you don't want to happen. Bottom line: originally sealed brake fluid, no problem with shelf storage; opened containers, don't save, but recycle the remainders at your local recycling center.

(Yes, I am a chemist by profession.)

While your thought is correct for a single compound product like DOT 4 brake fluid, it does not hold true with engine oils due to oil having a complex system of additives, some of which are just to hold the mixture togeather. This is why all oil manufacturers date mark their containers and typically suggest no more than 2-4 years shelf life (varies by brand) for unopened containers of full synthetics, less for opened ones.

[Dario Campolattaro]

Check out the big brain on carrera3.2. Cool.

[Dennis Nicholls]

Nobody near Boise stocks the ATE brake fluid.  But O'Reilly's (of all places) does stock the Pentosin Super DOT 4 brake fluid, and at a reasonable price.  Porsche uses Pentosin for other items (e.g. power steering fluid).  Is their brake fluid OK to top up the dealer fill? 

 

Now that I've got the tranny pulled I see what a pain it is to access the clutch slave for bleeding.  The dealer who sold me the car replaced the brake fluid and flushed the brakes just before selling it, but now I'll bet he skipped flushing the clutch slave.  I should use my HF copy of the mityvac to flush the clutch line while the access is better after reinstalling the tranny.

 

EDIT  I think I answered my own question.  Pentosin's data sheet says this product has been given Porsche ref. # 000 043 203 66, which is what a liter of dealer Porsche brake fluid is marked.

Edited June 19, 2014 by Dennis Nicholls

[JFP in PA]

Nobody near Boise stocks the ATE brake fluid.  But O'Reilly's (of all places) does stock the Pentosin Super DOT 4 brake fluid, and at a reasonable price.  Porsche uses Pentosin for other items (e.g. power steering fluid).  Is their brake fluid OK to top up the dealer fill? 

 

Now that I've got the tranny pulled I see what a pain it is to access the clutch slave for bleeding.  The dealer who sold me the car replaced the brake fluid and flushed the brakes just before selling it, but now I'll bet he skipped flushing the clutch slave.  I should use my HF copy of the mityvac to flush the clutch line while the access is better after reinstalling the tranny.

 

EDIT  I think I answered my own question.  Pentosin's data sheet says this product has been given Porsche ref. # 000 043 203 66, which is what a liter of dealer Porsche brake fluid is marked.

 

The Pentosin product is a fine alternative to the ATE product.  A lot of people tend to skip the clutch when flushing the system because the bleeder is in a somewhat tight space.