Well, I'm going to be doing a major brake job here pretty soon and am wondering what your guy's preferences are on hydraulic fluid such as DOT 3, DOT 4, DOT5, and between the different brands available. Also, I'm looking at hydraulic fluid for the clutch too. Thanks for the help guys.

 

No comments on this?

 

What are you doing with the car?

There's not much variation between brands as far as "quality" of fluid. The DOT # just signifies the boiling point. Higher the number, hotter you can run the fluid.

I run DOT 4 in any car I track.

 

I'm going to be replacing the pads and rotors on all 4 wheels and am going to be completely bleeding the brake system and checking everything over. I was also debating switching to stainless steel lines, but have heard a lot of bad things about them rupturing, and that they are not recommended for a daily driven vehicle. The same thing was said about the stainless steel clutch lines too.

I remember reading that to use DOT 5 you had to have different lines or something, and that the car needed to be bled a certain way in order to use it. I know that DOT 4 is better than DOT 3, and will be using that if I can't use DOT 5. I know there's a few different companies that make brake fluid, and was wondering if any certain companies made fluid for a racing application that had a higher boiling point.

 

can DOT 3 and 4 be mixed? like if I bleed DOT 3 fluid and put DOT 4 in, or I guess topping off 3 with 4 or vice versa...

 

Never heard of that before? Could be wrong, but I doubt that the lines will give any trouble to fluid with a higher boiling point.

Its not "better". In fact, during street driving you will not be able to tell the difference between the two. Only after overheating the DOT3 fluid will you notice the difference, because the DOT4 will still be providing braking power. Thats the only difference, one boils at a higher temp.

There's a company that makes blue fluid which is supposed to be able to be boiled and still retain its DOT# rating......can't recall who makes it though. And I wouldn't trust that claim anyways. But the short answer is even a "racing" brake fluid container will have a DOT# and thats what the rating is.....whether it says racing or not.

Sure they "can" be mixed.......but you shouldn't.

 

I am wondering why you aren't able to use DOT 5 in normal vehicles then and why they only recommend DOT 3 or DOT 4. I was wondering if it had to do with the composition of the DOT 5 fluid or something then. Also, is there any advantage whatsoever to using the stainless steel lines? All I seem to hear is bad things about them...

 

as far as i know you can mix dot 3 and dot 4 all day long but unless you are doing something crazy like totally retrofitting the entire brake system i would stay away from switching to dot 5... if you mix even the smallest amount of dot 3/4 with dot 5 you will contaminate your brake system and have to replace every rubber part in it. we played with some dot5 up at the shop one day and found out it likes to eat paint like nobodies business too....

as far as mixing dot3 and 4 together goes i would recommend sucking the reservoir as dry as possible, filling with dot4, and then gravity bleeding all four wheels until clear fluid starts coming out... try to avoid pedal bleeding though because its hard on the cups in the master cylinder.

you can do the same thing to your clutch.

the thing about braided steel lines rupturing is a myth but also very true. when purchasing lines stay away from anything thats not DOT certified. that means anything on ebay! if you find lines that are DOT certified they will most likely be more expensive but will be VERY durable. you should read up on the tests they put them through they do some wild **** to them.

 

brake fluid normally eats paint like nobody's business, but maybe DOT 5 is even worse...

 

DOT 5 is very harsh on rubber, and that is the main reason why. It will eat the flex lines (even stainless lines have rubber inside) and the seals in the pistons if the material isn't compatible. I don't know if it is.....more then likely isn't. How hard do you drive this car anyways? During lapping at Mosports big track I have a hard time boiling DOT 4. Its no race car, but I run the **** out of it. WTF do you need DOT 5 for?

There's advantages...but very, very minor ones.

They can increase "pedal feel" and this is entirely true. However, the comparison of pedal feel is being made between a car with 20 y/o rubber lines that should be replaced anyways, to a new stainless (thus no swelling) line.

New rubber would perform just as well, and in my experience has.

The downsides are possible leaks/failure (somewhat uncommon, but does happen) as well as finicky setup. You don't want the line to wear your tire when the wheels are at full lock etc. or rub the strut...or anything for that matter. So they need to be positioned just "so".

Thats why I said you "can" but whats the point? You end up with a boiling point in between the two, and DOT4 is typically more expensive. So why would you mix them unless its a pinch case where you need to top it off or something?

If you're switching fluids entirely, as you mentioned, you can simply start filling and start bleeding until the whole system is purged. Thats the other reason they make the blue fluid - the second its purged, you know it.

 

I use this stuff (AP551): http://www.raceshopper.com/ap_brake_fluid.shtml

There's a racing shop near me that sold me a bunch of it for cheap.. I can't tell you if I noticed a difference between the fluids, because I replaced the master, booster, rebuilt my calipers, and bled my brakes all at the same time.... so.... does it work great.. .Sure... I can lock my tires pretty damn easy and I haven't experienced any brake-fade yet... Even on long steep hills with constant braking force.... no fade. So, good stuff in my opinion.

 

ATE Super Blue. great stuff and doesnt need to be change quite nearly as often as Motul. ATE offers a yellow fluid used when you bleed the brakes so you know all the old stuff is out

 

All brake fluids absorbe moisture. Once a can is opened it is recommended to throw it out after six months. The moisture (usually condensation) contaminates the fluid. DOT 4 is a wonderful upgrade over DOT 3. IT has a higher boiling point. Run a pint through the system after you have completely bleed the old DOT 3. Use the pint of DOT 4 to fluh out the system. Refill the system and do a good bleed. Dont mix the two together. Your defeating the purpose of using DOT 4.
Flushing the brakes should be done every two years. However, most people wailt for a brake failure.

 

I've used Valvoline SynPower in just about everything I've owned for quite a while now. Decent price, good performance for auto-x and light lapping days, easy to find. If you're not planning heavy track use it's a good choice IMO.

 

Technically though, DOT 4 is better than DOT 3 since it does have a higher boiling point, but most cars will never see the boiling points of either anyways. I'll probably just use DOT 4.

Here's the scoop behind DOT 5:

We do not recommend using DOT 5 fluid in any racing applications. DOT 5 fluid is not hygroscopic, so as moisture enters the system, it is not absorbed by the fluid, and results in beads of moisture moving through the brake line, collecting in the calipers . It is not uncommon to have caliper temperatures exceed 200 F, and at 212 F, this collected moisture will boil causing vapor lock and system failure. Additionally, DOT 5 fluid is highly compressible due to aeration and foaming under normal braking conditions, providing a spongy brake feel. DOT 5 fluid is best suited for show car applications where its anti-corrosion and paint friendly characteristics are important.

I understand there's no point in mixing them unless you need to because it's leaking. Your best bet is just to bleed the system and use new fluid from a sealed container.

I've heard too many bad things about the SS lines to not want to use them, especially for the people that have used them for their daily drivers. They seem to like to rupture at odd times and cause problems.

Now my other question. What is the best way to go about bleeding the brakes? I've done the pedal bleed and vacuum feed before, and I've heard there's also a few other ways to do it. What's the best route to go?

 

What kind of driving are you doing? WIll you be going to the tracks?

I would ask myself that first off. The differnce or getting normal lines and normal brake fluid is a lot compared with ss lines and exotic brake fluids. Mainly its the ss lines though

 

I like Motul RBF600 myself. We use it endurance racing and it holds up well.

 

Castrol makes a "gtlma" it is a Dot3/dot4.. I will use that..

ATE super Blue is compressible.. it is great for track use but not so great for a daily driver..

Dot 5 is silicone thus why it cannot be mixed with 3 or 4

 

I will be doing some tracking, but mostly daily diving. I just read too many bad things about the stainless steel lines to not want them. Not only have I heard bad things about the brake lines, but also the clutch lines. Of course I don't want a fluid that's going to compress, so that's a major thing to keep in mind. What is the best way to go about bleeding the brakes? I've done the pedal bleed and vacuum feed before, and I've heard there's also a few other ways to do it. What's the best route to go?

 

The DOT rating is just the minimum spec. Ford DOT3 fluid boils at 550 degrees for the old formulation, which is still available in places. I can still get bottles of it made by Prestone. It's a very good deal for such a high boiling point and is more than enough for most track use.

For street use Castrol LMA is good because it's not very hydroscopic.

 

Black 91 is on the right track. Dot 4 does not guarantee a higher boiling point. I use the Dot 3 Ford heavy duty in my IT car with great results. It has, as was stated a 550 boiling point.

I use Castrol LMA in most of the street cars. LMA stands for "low moisture absorption" which in simple terms, means condensation doesn't invade it nearly as much.

Dot 5 brake fluid is silicone. I use it in my big Healey because it sits for months at a time in storage. Silicone brake fluid will not allow moisture to penetrate it in any way. The most valuable aspect of silicone brake fluid is that, in those cars that sit for extended periods, the brake lines aren't as likely to rust. Real Dot 5 silicone should not be used in cars that will be driven in any competitive event. It generally has a much lower boiling point than the heavy duty 3 or 4. Also, real Dot 5 silicone brake fluid will not harm paint.

Remember........I said REAL Dot 5 silicone. Read the labels carefully.

I hope this helps clear some of the confusion.

 

So basically you should be looking for the highest boiling point and something that's slightly hygroscopic. Something that's not hygroscopic will not absorb the moisture that gets into the system and thus cause problems with rust and a spongy brake pedal.

 

Ok so I dont know what the previous owner used for any of the fluids in the car. Do I start by just draining the system then running the new stuff through to make sure all of the old stuff is out? And then just fill and bleed with the new stuff?

-Manavapor

 

Yes. You'll want to bleed all of the old fluid out first, then start putting in your new fluid and using it to flush out the rest of the old stuff. After it starts coming out perfectly clear like the new fluid, you can fill it up and seal things off.

 

NOOOOOO!

If you drain it then refill it you'll never get all the air bubbles out. Just keep pushing fluid through untill it looks like it did when it went in.