Stratifying Brake Fluid

[w.a.nelson]

Here's one for you. Any thoughts?

I'm changing brake fluid; replacing ATE Racing Super Blue with ATE Type 200 Amber. ( By the way, do you know that Racing Blue is no longer manufactured/ But that's another story. )

Should be a straightforward job, right? I am using the Motive Power Bleeder. Siphon out as much blue as I can from master cylinder. Fill bleeder with amber, pump up to 15 psi, and start bleeding. Fluid flow starts out as clearly blue, then begins to fade, goes to almost clear, but doesn't go to clearly amber in color. Same for all four calipers. At end of process, there is still blue fluid visible in master cylinder - a layer about 1 inch deep, and it is sitting on top of what is clearly bright amber fluid that occupies the balance of the master. This is weird to me.

I wonder if there is a difference in the specific gravities of the two fluids. Call ATE, and they say " no, the properties of the two fluids are the same except for color. " Talk with Motive, and they say they have not seen this before.

Today, I draw off as much of the blue fluid from the top of the master cylinder as I can, and then repeat the bleeding process, using more fresh amber fluid. Still getting blue fluid at each wheel to start with. Not as dark as yesterday, but clearly blue. Changes to progressively lighter blue, and then goes sort of clear in appearance. Does not turn to full amber color. At end of 4 wheel process, master cylinder still looks from the side as if it has a layer of blue sitting on top of amber - perhaps 1/8 inch deep. Looking into master cylinder from the top, the fluid you can see is definitely amber. Perhaps the master cylinder is discolored from the blue at the "max" level, and that is what I am seeing from the side.

At this point, I don't know whether to repeat the process again, or if it is OK the way it is?

Don't know what caused the stratification yesterday.

Interestingly, the bled off liquid that is in the catch bottle from today, which I assume to be a mix of what was a blue stream, turning to clear, to perhaps light amber, has stratified in the bottle, with amber on the bottom - say 1/2 inch - and blue on the top - say 2 inches. Too late in the day to call ATE about this; will call tomorrow.

Any thoughts about what I am seeing; whether I'm OK at this point; or where to go from here? I really wasn't planning on this turning out to be a big hassle!

Thanks.

 

[fjpikul]

Mr. Engineer, you are aware there is a bleeder on both sides of the caliper? I'm not trying to bust you, but sometimes even Ford trained techs miss this. Perhaps Indy could chime in?

 

[Fubar]

Would the moisture in the fluid play a role in this mystery? Although, I would think of the results as being opposite this reaction. Unless, a bad batch is being installed?

 

[ultrasportracing]

Just another precaution, make sure you calliper pistons are fully retracted, may need spacers if pads are a little worn,, some of the original fluid will be trapped in the calliper bore, and not be bleed out..

 

[w.a.nelson]

Yes Frank. I've certainly made many blunders worse than that in my day, but I did catch that one. If only the answer were that simple. Thanks.

 

[bret a ewing]

Huh, just read about ATE SuperBlue. I would hope it could be sold "non-DOT" for guys like us who flush between colors.

I don't need another collector's item.:wink

 

[Indy GT]

Just another precaution, make sure you calliper pistons are fully retracted, may need spacers if pads are a little worn,, some of the original fluid will be trapped in the calliper bore, and not be bleed out..

Ultra, from a technical perspective, I see no correlation as to piston position while bleeding the system and fluid flushing. When flushing a brake caliper your goal is to replace all the “old” brake fluid with “new” fluid. The fluid volume in the caliper is determined to a minor extent by piston position within the bores of the caliper. Pistons retracted in their respective bores (as with new brake pads which push the actuation pistons away from the brake disk toward the caliber body) lower overall caliper fluid volume. Conversely, pistons extended within their bores (with worn brake pads which allow the pistons to extend toward the brake disk) increase caliper fluid volume. The delta volume is not very large relative to the total overall brake fluid volume.

IMO the relative position of the actuation piston within the caliper bore does not impede or in any way defeat the fluid flushing process. It might just alter slightly the amount of fluid needed to perform the flush. I see no way in which piston position in the bore can “trap” fluid within in the bore. All the piston position within the bore can do is alter the bore fluid volume.

As to the stratifying fluid experienced by w.a.n, that is indeed perplexing. I have used both ATE fluids for some time and have recommended the alternate super blue/amber exchanges to many. I have never experienced any stratification observations. And I agree, the manufactured density of both fluids should be identical. The only difference between the two fluids is the addition of blue dye in the super blue to aid in visual observation of a complete fluid change. But obviously with your stratification observation there HAS been a density change in your original super blue formula. Since non-silicon based brake fluids are by nature hygroscopic, I would opine the most likely reason for the density shift is due to moisture absorbed by the blue fluid over time.

Since you have flushed the system twice so far, I would do it one more time to try to purge the last volume of blue fluid from the system and consider performing the fluid replacement on a more frequent basis.

 

[ultrasportracing]

As to the piston position,, With dealing with racing cars, we have found that pushing the piston back to its seated position, is the only way to get a total fluid change, has fixed a lot of brake issues, seems the new fluid will take a short cut and go straight from the inlet port, straight up to the bleed valve, leaving contaminated fluid in the piston chamber, Will be worse the more wear is on the pads.. Just talking from experience, , will draw a diagram if it helps.

 

[ultrasportracing]

brakes

very quick over view of the above

 

[w.a.nelson]

bret,

Apparently there is no hope for additional supplies of Super Blue. Some folks have it in inventory, or have personal supplies. Ate's recall program provides for refund of your purchase price ( and supposedly shipping cost ) if you return to where you bought it. I talked with TireRack, and they weren't into shipping costs. Details on Ate's website.

Indy,

Thanks. Good thoughts. I'm trying to get to Ate to see if there is any chance of some kind of manufacturing error? I will flush again, as the blue seems to be lessening each time. The thing that baffles me is that there is stratification in the catch bottle. I have 3/4 inch yellow(ish) in the bottom, and 2 inches on top of that.

Ultrasports,

Thanks for the thoughts and sketch - any chance of getting that signed? I don't think my pads are worn that much, but I'll see if I can retract the pistons any when I bleed again.

 

[Indy GT]

Ultra,

Thanks for taking the time to draw a picture for our owners and I understand your concept. What you offer is empirical evidence based on your experience. And that is fine; experience is great. But for GT owners to go to the trouble of wedging some object between the inner/ outer brake pads and the brake rotor to uniformly push the pistons back into the bores as you suggest is in my opinion overkill and overcomplicated. I see very little value-added to the flushing operation for the reasons below. The wedge operation is complicated by the use of 4-6 piston calipers which pose additional challenges for the owner to get each piston pushed back into its respective bore a similar amount.

Here in the US, Federal Motor Vehicle Safety Standards §571.116 Standard No.116; Motor vehicle brake fluids places many stringent and technical fluid requirements on producers of brake fluids. By this standard, paragraph S5.3, all US motor vehicles with a hydraulic brake system must use fluids in conformance to Standard No. 116. And within the non-silicone base brake fluids (DOT3, DOT4 and DOT5.1) the specification requires all these fluids be miscible. See paragraph S6.10 “Compatibility”. Thus they all are required to mix and do not stratify.

When flushing a caliper, the new fluid is introduced at the lowest region of the caliper and the brake bleeder fitting is located at the highest elevation point on the caliper. You correctly show this on your drawing. This is to enable removing all air from the caliper volume which is compressible. We want the caliper completely filled with incompressible fluid without any air. There are a number of mechanical perturbances located inside the caliper volume. These could be casting/forging area changes, springs, piston posts, etc. All of these features add turbulence to the fluid as it is introduced from the bottom of the caliper and thus promotes mixing of the fluids as the new fluid enters from the bottom and the old fluid is pushed out the top through the opened bleeder fitting.

When flushing an aforementioned system which had the ATE Type 200 with ATE SuperBlue, the initial fluid coming out of the bleeder fitting would be amber in color. As the new blue fluid was introduced and internal caliper turbulence mixed the two fluids the outgoing fluid would gradually change to a more blue color. After a sufficient amount of fluid had been pushed (or vacuumed) from the bleeder fitting the fluid would be totally blue in color indicating a full purge of the caliper volume. There is no reason for a “layer” of old fluid to remain on the internal piston surface (shown in your sketch) as the internal fluid turbulence along with the DOT required fluid miscibility will mix and expel the old fluid when the color has fully changed. Even in the remote chance there is any remaining old fluid left in the caliper volume, the amount of water absorbed in this volume is infinitesimally small relative to the new volume of brake fluid introduced during the flushing operation and thus the wet boiling point (brake fluid which has absorbed water vapor) has increased significantly relative to the old fluid’s characteristics.

Thanks again for sharing your experiences.

 

[BlackICE]

I still have a few cans in a private stash.

http://hooniverse.com/2013/08/16/braking-news-ate-super-blue-deemed-illegal-for-us-distribution/

 

[Indy GT]

Ice, that is a good post and the cited reasons for discontinuation are (unfortunately for us) accurate.

Per §571.116 Standard No. 116; Motor vehicle brake fluids – fluid colors are dictated by paragraph:

S5.1.14 Fluid Color. Brake fluid and hydraulic system mineral oil shall be of the color indicated:

DOT 3, DOT 4, and DOT 5.1 non-SBBF—colorless to amber.

DOT 5 SBBF—purple.

Hydraulic system mineral oil—green.

So since all US motor vehicles with hydraulic brakes must use Standard #116 compliant fluid, the non-silicon based fluids are required by regulation to be colorless to amber making SuperBlue noncompliant.