what brake fluid

[Wyflyer]

I've got the BC Broncos brake booster kit, with all new lines & hoses, new wheel cylinders, and 79 Bronco/F150 front discs.

What brake fluid does this system need?

 

[SteveL]

I run dot 3. The 5 gets contaminated and breaks down to easy for my liking.

 

[charlie6976]

I'm using dot 4. Dot 3 and dot 4 are inter changeable with dot 4 having a higher boiling point. Dot 5 is different for newer (40 years newer) systems. Research brake fluid dot 3,4 and 5.

 

[bknbronco]

get the same stuff walmart has been selling for 20 years.

 

[Apogee]

A good quality DOT3 fluid will be more than adequate for most EB applications, or if you really intend to beat on the brakes, DOT4. I usually run Valvoline DOT3/4 Synthetic Brake Fluid (blue and white bottle) in my '77 EB and '77 F150, as it's affordable, decent quality and readily available. You can't beat 32 fl oz for less than $5 at Walmart IMO. Given it's relatively low cost, I can easily justify flushing the system every 1-2 years to keep things fresh and to remove whatever water has worked its way into the system.

On my higher performance brake applications, I run Motul 600, Wilwood EXP Plus or some other comparable DOT5.1 glycol based fluid.

I avoid the DOT5 silicone based fluids like the plague, as I don't like the relatively spongy pedal feel they provide nor the fact that they are not miscible with water.

 

[Pa PITT]

MY 1ST THOUGHT ALSO JUST DOT3 OR 4. Avoid 5

 

[whmoorejr]

Weird. I've never used 5, but always wanted to. (But you have to start with a whole brand new system for optimal results). I always heard that because it is the only silicone based brake fluid, water won't mix, it will separate in the system and the water can be bled out (versus dot 3, 4, 5.1 where the water will mix with the fluid and corrode the whole brake system over time).

 

[Apogee]

Weird. I've never used 5, but always wanted to. (But you have to start with a whole brand new system for optimal results). I always heard that because it is the only silicone based brake fluid, water won't mix, it will separate in the system and the water can be bled out (versus dot 3, 4, 5.1 where the water will mix with the fluid and corrode the whole brake system over time).

It's actually the opposite...because glycol-based brake fluids (DOT3/4/5.1) are hygroscopic, they will bond with the water. So when you bleed the system, not only will you remove the brake fluid, but also the water it has captured. The brake fluid will keep grabbing water until it reaches its saturation point, but it will still have a "wet" boiling point significantly higher than water.

DOT5 silicone fluids don't mix with water, and water is denser than silicone brake fluid, so it settles in the low points of the system...usually the calipers. The bleed screw is at the top of the caliper to remove air, so the water stays in the bottom of the calipers. Over time, the water builds up and eventually you end up with a localized corrosion on the bore/piston while everywhere else looks brand new. While the brake fluid may not boil under over 500 degrees F, the water pretty consistently boils right around 212, thus defeating the purpose of the brake fluid.

Tobin

 

[Broncobowsher]

DOT 3, 4, or 5.1
Not DOT 5

I generally go for DOT4. It is better then DOT3 at nearly the same price. The DOT5.1 is also compatible, but I don't have heat issues (and you shouldn't either) that mandates the higher expense. And all of these are compatible.

DOT5 is an oddity that is not compatible with anything else. In the 90's it was going to wave of the future. It didn't catch. There are fans of it. Great for show cars. Everyday use, it has issues. Sometimes big ones (like not compatible with normal seals).

 

[KyleQ]

I see this turned into the coolant thread - %)

DOT 3 - it isn't a race car and doesn't have fancy components that would require it.

 

[Wyflyer]

I've bought some Dot 3, just haven't found time to put it in and bleed lol

 

[sykanr0ng]

If you drive in the mountains of Colorado and have an automatic transmission that does not give you compression braking your brakes WILL get very hot.
That is when you want higher temperature rated brake fluid.

I'm sure many will think that is so obvious, but many people that move to Colorado every year have no clue.