Dot 5 Silicone fluid opinions

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rod7515

rod7515

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Many years ago I did a complete rebuild of the brake system on my 74 corvette. I went with the Dot 5 silicone fluid because of the calipers on the vettes always end up leaking. Ive had no issues with it but have read where many don think it produces as good/solid a brake pedal. I was wondering if anyone has gone this route with your a bodies and what your thoughts were.
Thanks Rodney
 
I've been using 3 all my life. I see no reason to change now.
 
I was thinking of changing, Dot 5 from what I was told, gives a harder pedal...
Dot 5 also does not absorb moisture like Dot 3 and 4, and will not damage your paint if you spill some....all a plus as far as I can see!
 
I have 4 wheel drum brakes. Changed over to silicone years ago. Made a big difference at the end of the 1/4 mile. Not so much on the road. Picked up KH setup....havent installed them yet.
 
When we bought dads 67 cuda it had Dot 3. Had a leak at master cyl and peeled the fairly new paint. Said pi$$ on it and swapped over to 5 with zero issues. I can't give an honest comparison between the 2 in stopping
power.
No eating paint and no moisture absorption is good enough for me.
Factory non pwr discs so the stopping is good IMO
And Dot 5 is Plum Crazy Purple and tastes better than 3
 
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I run Dot 3,here's an excellent quote...
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Tech Question
Gary Boak, Chilliwack, BC, Canada, 1969 Dart Swinger 340

I notice in the April 04 issue you say that DOT 5 brake fluid can be used without flushing the system. Everything I have heard and read states that Dot 5 does not mix with anything except DOT 5. When switching to DOT 5 are you not supposed to use new rubber?

Gary-

Another old wive's (or Mopar Muscle) tale. First, realize that DOT specs don't specify the composition of the fluid, the rating relates only to the boiling point. So, therefore, it would be possible to have DOT 3 fluid that's silicone, and DOT 5 that's not (and this latter combination does exist.) These specs are covered in detail in Federal Motor Vehicle Safety Standard section number 571.116, which is part of the Code of Federal Regulations, #49, Chapter V, see for yourself at:

Code of Federal Regulations, #49, Chapter V
Here's an excerpt from the law on boiling points:

Equilibrium reflu point (ERBP). When brake fluid is tested according to S6.1, the ERBP shall not be less than the following value for the grade indicated:

(a) DOT 3: 205 ÌŠC. (401 ÌŠF.).

(b) DOT 4: 230 ÌŠC. (446 ÌŠF.).

(c) DOT 5: 260 ÌŠC. (500 ÌŠF.).

A recent change to the law specifies that non-silicone fluid meeting DOT 5 temperature specs. be labeled DOT 5.1. All DOT 5 fluid must be purple in color, all other grades must be clear to amber.

The baziilion pages of the specs relate mostly to boiling points, viscosity, and the fluid's effects on rubber (swelling), as well as testing procedures. But there's also much written about compatibility. What has probably caused the confusion is that DOT 5 fluids are tested differently than other types, but these tests apply equally to silicone and non-silicone fluids. Subchapter S6.5.4 addresses miscibilty, specifying that the fluid being tested must mix with a standard type fluid, and this miscibilty test DOES apply to DOT 5 fluids, and can't gel, swll cups, etc. when mixed. So there!

The Society of Automotive Engineers (SAE) also has detailed specs: J1703 and J1705.

It's true that much has be written saying that silicone based fluids cannot or should no be mixed with other types, this is that old myth-perpetuating deal. Nowhere can I find a scientific study or analysis to back this story up - do a Google search yourself if you don't trust me.. There's only been two studies on this that I'm aware of: Dow-Corning, the leader in silicone brake fluids (possibly the only true USA manufacturer), did a detailed study almost 30 years ago, wherein a system was haphazardly swapped from DOT 3 to silicone, with the intent of leaving a significant portion of the fluid UNchanged. The system passed all DOT tests easily. The second test is less scientific, but, to me, more significant: Yours truly has been using DOT 5 silicone in every car I've owned or serviced since approx. 1978. I have never flushed a system! I have, in some cases, bled out most of the old stuff, in other cases, I've just topped up a DOT 3-filled system with silicone. Cars serviced by me in this fashion have stopped will from speeds over 160 MPH. I've never had a stuck caliper (or wheel cylinder) pistion since making this change universal in my fleet - even in cars stored for long periods. I've also never damaged pain from a brake fluid spill. Come to my garage - you will find 4 or 5 bottles of DOT 5 silicone, and zero of DOT 3 or 4.

On your Dart, do what I do (and say): bleed out as much of the old garbage as you can, until you see purple at each bleeder screw. And don't worry about it!

End of story.

Rick Ehrenberg

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Thanks abodybomber, good read. I also thought the entire system had to be changed out to change types. Ehrenberg is a smart dude.
 
Why would you have brake fluid on your paint?
..for our cars dot 3 or 4 is fine ...as it has been for the fifty years we used it before silicone arrived.The same applies for purple oil and purple air cleaners,but it's your money.
 
Dot 5 all the way.
All around better brake fluid.
Just like synthetic oils, technology people.
 
The main problem I would have with swapping to Dot5 and not completely removing the old stuff would be that you would still have some fluid that absorbs water in the system, and very likely right where you didn't want it like in the caliper and cylinder bores.
 
TrailBeast said:
The main problem I would have with swapping to Dot5 and not completely removing the old stuff would be that you would still have some fluid that absorbs water in the system, and very likely right where you didn't want it like in the caliper and cylinder bores.
Click to expand...

..some would argue the water absorption is a good thing.Silicon apparently does not absorb moisture so it will pool in any lo spots in your system and cause corrosion more quickly.
..these arguments could go on forever but either will work well in our cars.For a race car the higher boiling point of dot 4 or 5 is necessary whether it's silicon or not.
 
Nothing wrong with DOT3 so I will keep usin it. Never had it boil so I guess I am ok.
 
LMAO..Since when are car guys not worried about peeling paint and the possibility of eliminating it ever happening by spilling or a leak? IMO...worth every penny DOT 5 or DOT 5.1... Moisture absorption DOT 3-4 ...moisture pooling in areas when using silicone DOT 5.1? Really..?? non issue.. rust is an issue though...
 
I agree ask anyone what brake fluod does to paint?
EVERY gearhead has spilled some sort of **** on their car lol beer blood sweat whisky oil and yes brake fluid **** happens right?
 
I use DOT 5 silicone in all my non-ABS cars. The pedals are hard. I recently replaced the 1 pot cast-iron MC in my 65 Newport to a dual MC (for safety). After ~10 yrs w/ silicone, it was spotless inside. The military uses/used DOT 5, indeed I have bought 1 gal mil surplus cans. People that suggest it is bad because water that drips in the reservoir (anyone that stupid?) won't be absorbed, must have that imagined problem with their power steering reservoir. I have always changed to DOT 5 when redoing the system, so flushed the tubing well, but there is no incompatibility problem, just that any leftover nasty glycol (DOT 3, 4, or 5.1) are places that may rust, as TrailBeast mentioned. Re paint removal, has anybody seen an old A that didn't have the firewall all rusted underneath the MC? I have used old glycol as a cheap paint remover.
 
You really think it's cool to call people stupid because they prefer one type of fluid over another?

I don't really give a damn about the reasons. I just use DOT3. I don't really care who uses DOT5 or why, but I wouldn't call them stupid. Why don't you go back to grammar school, Bill?
 
Rusty, re-read my post, then take aim. I wasn't going all Trump, and not even directed at you. I simply suggested that anyone who lets water drip into their brake reservoir is stupid. Same for the power steering reservoir, transmission fill tube, rear-end, ...

I use glycol (DOT 4) in my 2 minivans, since they have ABS and all DOT 5 bottles disclaim, "don't use in ABS system". I doubt that matters, but don't want a lawyer jumping on that to explain why his client ran into the side of me. I flush thru new fluid every 5 yrs or so. Prudent to flush more often in GA. Every used car I have acquired has had rusty fluid come out, so guessing they didn't understand the need to flush. My new 1982 Chevy S-10 had a leaking, rusty wheel cylinder at 4 yrs. That was in Atlanta, but I still wonder what the GM workers filled it with. You won't offend me by using glycol, indeed silicone is getting harder to find, w/ only motorcycles appearing to ship with it today. I am just offended by people spreading mis-truths about silicone. And don't waste your money on "synthetic" brake fluid, since all types have always been synthetic (i.e. no mineral oils).
 
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The silcone fluid is higher compressiblity, so ultimate performance is lower.

Because the fluid doesn't absorb moisture doesn't mean you don't have water in your brakes. So you may get water particles completely separate from the brake fluid.

In general I'd tell you to use a DOT4 like ATE Typ 200 in these cars and SL.6 in an ABS equipped ride.

In an ABS vehicle, it will perform better with low viscosity DOT4 by a lot. In these...doesn't matter there.

You wont find any OEM or any race team using DOT5 silicone. If it was better they would. They are using DOT4 borate ester based fluid.
 
Blah blah blah...
DOT 5 works fine. Stops when you press the pedal, doesn't eat paint. Don't overthink it.
 
KnuckleDuster said:
Blah blah blah...
DOT 5 works fine. Stops when you press the pedal, doesn't eat paint. Don't overthink it.
Click to expand...
Yep, because how they perform is totally irrelevant. Not like it's anything related to performance or safety at all. 9" drums stop when you hit the pedal too. It might only be once, but who cares, right?

Sure, use whatever you want, however if you're asking for an opinion of someone who actually works on OEM brake systems as day job, and has a reason to care, I wouldn't use silicone DOT5.

And before I get jumped because Ehrenburg said something, he can be wrong too, his opinion is also not backed up by any data. There are exactly zero silicone DOT3 and DOT4 fluids.
 
Nothing personal, but show me YOUR hard data to prove silicon DOT 5 is inferior?
 
Really...no offense intended.
It just gets tiresome reading five-page threads where ten guys are arguing about whether water is wet.
I use DOT 5 in a factory Kelsey Hayes disc/drum setup and it feels comprable to newer cars. If somebody could prove DOT 3 stops 3ft shorter my ears are open.
 
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