DOT 5 Brake Fluid

Well, once again learned that you can't believe everything you read. Just tried DOT 5 silicone fluid for the first time. The big selling point for me was that it was not supposed to harm paint. Surprise...it does...big time. A small seep on the reservoir took my new PPG paint off better than any stripper I've ever used.

I would have been much more careful about checking for leaks if I were using the old fluid...didn't know I needed to with this purple stuff. FWIW...don't trust your paint with this stuff. Treat it like the old DOT3/4

John

What brand of DOT 5?

Was it DOT5 or just Synthetic?

Sorry to hear it John.

In over 21 years with DOT 5 purple silicone fluid have I ever had any paint come off. If it got soaked because a gland was not sealed tightly, I would just wipe up the oily mess from the paintwork. And that covered 105,000 miles with no issues like you describe. Maybe your painter didn't prepare the epoxy etch primer, the primer and the finish colour correctly.

...interesting. Never knew DOT 5 was considered paint safe in the first place.

Oil, brake fluid, brake cleaner, WD40, Windex or anything other than wax or soap has always been kept away from painted surfaces for me.

DOT 5.1 is fully synthetic but not silicone and it will strip paint like any other DOT 3, 4. It just has a higher boiling point.
DOT 5 is silicone and doesn't strip paint.

prb51 said:

DOT 5.1 is fully synthetic but not silicone and it will strip paint like any other DOT 3, 4. It just has a higher boiling point.
DOT 5 is silicone and doesn't strip paint.

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What he said.

John,

Do you have more information on brand, place of purchase and whether it was DOT 5 (silicone) or DOT 5.1?

Scott

Dot 5 will not eat paint but if you ever have to repaint it is almost impossible to get the area clean enough to redo without getting fisheyes.
Use fisheye remover in your gun and you can toss it too, because fisheye remover contains.....you guessed it....silicone.

Still I guess its better than having your new paint job eaten away.

Darwin said:

Dot 5 will not eat paint but if you ever have to repaint it is almost impossible to get the area clean enough to redo without getting fisheyes.

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Fish-eye causing silicone can come from many sources besides silicone brake fluid, including some "miracle waxes", car wash "quick wax", and even Armor-All. Takes a special solvent to get it off the surface. This stuff works for me:

HerronScott said:

John,

Do you have more information on brand, place of purchase and whether it was DOT 5 (silicone) or DOT 5.1?

Scott

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I seem to recall that DOT5/silicone fluid is patented. There are (or were) only two manufacturers, GE and Dow. Everything else is just rebranded. It is always purple in color.

I tested it (on purpose) on a panel sprayed with Glasurit acrylic urethane; left it sit for days. It wiped right up, no damage.

DOT-5 has not damaged any paint I've tried it on! As Scott says, it's purple in color. A little experiment I did to prove that it will not mix with DOT 3/4 is shown in the photos below. The left tube in the first photo shows DOT5 pured on top of DOT 3/4. It is a direct indication that they don't mix! The right tube in the first photo shows what happens when they are shook up. The right tube in the second photo shows what happens after just 15 minutes of setting. Notice where the DOT 5 is now. A microscopic air bubble reaction has taken place and the 5 has pushed the DOT3/4 to the top. More indication that they don't mix. Should you try to change over to 5 and don't clean the system thoroughly, as in wheel cylinders and master cylinders where the 3/4 can be trapped, a reaction will occur. Not something you want happening in a braking system! Just thought I'd throw this bit of info in. PJ

PAUL161 said:

The right tube in the second photo shows what happens after just 15 minutes of setting. Notice where the DOT 5 is now. A microscopic air bubble reaction has taken place and the 5 has pushed the DOT3/4 to the top. More indication that they don't mix. Should you try to change over to 5 and don't clean the system thoroughly, as in wheel cylinders and master cylinders where the 3/4

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More likely is that the purple colorant was extracted into the DOT 3/4 upon shaking. But yeah - they don't mix.

Well I'm baffled... John does describe it as being purple in color, surely the 5.1 stuff wouldn't also be purple? I considered the addition of color to just be an identifier (like av-gas etc).

I have used DOT5/silicone for more than a decade w/o ever having any paint affected -- in 10 years I have managed to spread it around some including an explosion of the stuff when a stubborn caliper piston finally let go (was using the hydraulic system to move it).

Have also had 2 cars resprayed (professionally) without any issues even after 10 years.

So perhaps Randall's is the pertinent question -- what brand was this?

The brand I used is Gunk, and it says "Silicone DOT 5" on the can. It does not say 5.1 or anything else on the container. I painted myself...PPG DLP90 epoxy primer over sandblasted surface. DBC color with Urethane clear. The paint set for 2 months before the fluid leaked on it. The purple fluid saturated into the paint, and the whole area bubbled up...like a big ugly purple blister.


Like Darwin pointed out...I can only imagine how much fun I will have getting the silicone removed to repaint. I'd love to send a pic - if you guys can explain to me how to post pictures on this forum!?!

PAUL161 said:

Should you try to change over to 5 and don't clean the system thoroughly, as in wheel cylinders and master cylinders where the 3/4 can be trapped, a reaction will occur.

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"Not mixing" is different than "not compatible". I have done several conversions now without cleaning thoroughly, and the results have been excellent. Since they remain totally separate, there is no "reaction" between the two types of fluid.

And as Brent noted, the apparent inversion is because the purple dye gets sucked into the glycol.

CJD said:

The brand I used is Gunk, and it says "Silicone DOT 5" on the can.

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Thanks! I will definitely avoid that brand!

There is nothing in the DOT 5 specification about damage to paint, and "DOT 5" fluid is allowed to be up to 30% non-silicone. So apparently Gunk is putting something in theirs that does attack paint.

Hmm, I wonder if this also explains the stories of seal incompatibility that I've heard?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Like Darwin pointed out...I can only imagine how much fun I will have getting the silicone removed to repaint.[/QUOTE]
Get the Acryli-Clean, use it according to directions. It's also best if you do the painting away from where you did the surface preparation, as it's possible to get tiny droplets of silicone floating in the air.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:] I'd love to send a pic - if you guys can explain to me how to post pictures on this forum!?! [/QUOTE]
Several ways to go about it, none especially simple. IMO the easiest way is to go sign up with https://photobucket.com/ and put your photos up on their site. Then if you let your mouse hover over a thumbnail, you'll get a pop-up menu with several choices :



Click in the area labeled "IMG Code". Then navigate over to your BCF post, click where you want the photo to appear, and press Ctrl-V (assuming you are running Windoze, I don't know the Mac equivalent). You'll see some text that looks like
<div class="ubbcode-block"><div class="ubbcode-header">Code:</div><div class="ubbcode-body ubbcode-pre" ><pre> </pre>[/QUOTE] but when people view your post (or you click the 'Preview' button), it will appear as

I love this web site, it's just like having access to your own personal lab. I have also used Dot 5 for many years in my TR3, have gotten it on the paint and have never had any issues with it.

I just had a look at their product data sheet and it says this:
<span style="font-style: italic">OUTSTANDING PROPERTIES: Meets or exceeds Federal Motor Vehicle Safety Standard #116. DOT 5 will
not absorb moisture and <span style="text-decoration: underline">it will not harm painted surfaces.</span> DOT 5 does not promote brake system corrosion,
its physical properties do not deteriorate with time and it insures long term braking performance under
extremely high and low operating temperatures.</span>

HOWEVER the claim is worthless since this statement is at the bottom of the data sheet:
<span style="font-style: italic">NOTICE: WHILE THIS INFORMATION IS PRESENTED IN GOOD FAITH AND BELIEVED TO BE ACCURATE, XXXXX COMPANY DOES NOT GUARANTEE
SATISFACTORY RESULTS FROM RELIANCE THEREON. THE DATA IS OFFERED SOLELY FOR YOUR INFORMATION AND XXXXX COMPANY DISCLAIMS ALL
LIABILITY FOR ANY LOSS OR DAMAGE FROM ITS USE. THOROUGHLY TEST ANY APPLICATION ACCORDING TO THE PRODUCT DIRECTIONS AND INDEPENDENTLY
CONCLUDE SATISFACTORY PERFORMANCE. NOTHING CONTAINED HEREIN IS TO BE CONSTRUED AS A RECOMMENDATION TO USE THE PRODUCT IN VIOLATION OF ANY
PATENT.</span>

All of this is why I haven't switched from Castrol GT/LMA!

CJD said:

Well, once again learned that you can't believe everything you read. Just tried DOT 5 silicone fluid for the first time. The big selling point for me was that it was not supposed to harm paint. Surprise...it does...big time. A small seep on the reservoir took my new PPG paint off better than any stripper I've ever used.

I would have been much more careful about checking for leaks if I were using the old fluid...didn't know I needed to with this purple stuff. FWIW...don't trust your paint with this stuff. Treat it like the old DOT3/4

John

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John, don't misunderstand, but this sounds very, very strange!!! Something is not right with this story, and frankly I do not believe that "proper" Dot 5 silicone would attack any properly applied, modern paint finish. There must be some key piece of information missing or incorrect! When we shot the test panels for Silverstone Grey, I asked Brian to paint an old coffee can. I use that coffee can for a container to catch old Dot 5 from the TR250 I replace all of the hydraulic brake & clutch fluid every 3 years. The paint is DuPont Chroma 2 part polyurethane. The inside of the "paint can" looks just as good today as it did 5 years ago, and still hard as a rock.