Lets start a fight- Brake Fluid

From my personal experience I have used DOT 5 just because it not hydroscopic like Dot 3 is . Silicon based. I have wheeled through water and actually had water in my brake system using the DOT 5 .After cleaning it out I had no corrosion issues like DOT 3 did . So I use DOT 5 with good luck . I also find that the DOT 5 also has a little less lubrication to it.
I used DOT 3 in my cj2A and under the same conditions it had corrosion isssues.ie Stuck wheel cylinders .

just my 2 cents

 

What did Willwood recommend?

On the other hand you are using stock wheel cylinders. With stock internals? You probably want to go with Dot 3 because that was what was available when those were first built, right?

 

No particular reason but I would choose DOT 5 with all new components.

 

I am about to install a new dual MC, SS lines, and new wheel cylinders in my 2A. It has 11" X 2" brakes from a mid-70s CJ5. I am interested to see what brake fluid everyone recommends.

 

An education indeed, just as you say. Your summary is excellent, and just the same as I have found.
People have strong opinions. My conclusion is that each type has it's particular pros and cons.

Personally I have used DOT#5 for 20 and more years in particular antique vehicles with no evident brake problems at all. I am sure that DOT#3 would have attracted corrosion.

But the relative advantages may depend upon your maintenance schedule (flushing) etc.

 

for aluminum . I would use Dot 5 . just because that's what you use on motorcycles .

 

1 vote for DOT 3...
Not brake related....but...I was up in the hills camping in my 66' Ford van back in the mid 70's & I tore a transmission cooling line off... I used water to get back home.

 

my Jamar line lock paper work says anything other than Dot5.

 

Everyone has a favorite brake fluid, just like engine oil. My favorite is DOT4, specifically ATE super blue, and amber. I like these two identical fluids (other than color) because when I flush the brake system every couple years, I can see when the old color is flushed out. I use this stuff in all my vehicles including classic British and modern German cars.
I will not ever use DOT5 silicone again. I used this stuff years ago, and found out the hard way it doesn't work in my climate. In high humidity, it doesn't absorb moisture, but the brake system still vents to the environment, so moisture enters the system and forms water drops that find their way to the lowest points of the system and sit there. Rust and/or corrosion pits wheel cylinders in just a spot, ruining them and causing leaks.
If you live in a very dry climate, this may not be an issue, but in deep south, it certainly is. At least with DOT 3 or 4, the moisture absorbs into the fluid and doesn't concentrate anywhere causing rust to form. Moisture in the fluid lowers the boiling point, but in most (non-racing) vehicles doesn't affect normal performance much, and thats why we are supposed to flush the system every couple years.
-Donny

 

DOT 5 has an advantage as stated above about not being hygroscopic. I don't use DOT 5 unless specifically stated to use it or on vehicles that will sit without being driven for very long times because if turbulence is encountered it can form air bubbles much easier than other brake fluids. This can make it a real pain to bleed the system or if the brakes are used violently air bubbles can form pretty easily in the system leading to a soft pedal.
We tried DOT 5 in our race cars. It was great for temperature resistance but under aggressive driving the above would happen and we would have braking issues. Went back to DOT 4 and problem solved.

Just what I've experienced. As usual, YMMV.

 

Dot3...use dot4 in VW...never had a problem...usually flush out every few years. It's cheap.

 

As some of you know my daily driver is a a stock optional CJ-3B.
It's all rebuilt original and/or NOS OEM parts.

The brake tubes all happen to be original.
They were removed and cleaned out internally using alcohol and pipe cleaners attached to a piano wire.
The Wagner wheel cylinders are all NOS from Kaiser.
The old stock Wagner master cylinder was previously used with Dot 3 in it.
It was cleaned, flushed, inspected then installed without a rebuild kit.
I've had Dot 5 in this system for over 3 years now with zero problems to date.

The Dot 5 fluid also makes a good wiping agent for the front axle hemisheres.
I soak the new hemisphere felt wipers with Dot 5 fluid.

At worst I'd say that the Dot 5 system was only slightly harder to bleed than Dot 3.

 

I tried Dot 5 in my hydraulic clutch and switched back to 4 after experiencing a flat pedal on a difficult trail. It may have been the aeration that Nick mentioned above. I bled the system on the trail and made it out OK, but got rid of the Dot 5 and have never had a problem with the clutch since then.

 

I really have a hard time imagining how aeration could happen to that extent. If it were possible, how could Harley-Davidson trust DOT 5, and the US Military?

 

This is why most manufacturers of vehicles with abs recommend DOT 3 or DOT 4 and recommend against DOT 5 silicone based fluid. Believe or not as you like, but we've had it happen.
The military and Harley Davidson is looking at storage issues with hygroscopic fluid they know they will have vs. other issues they may have.
Another advantage of DOT 5 is it tends not to eat paint like DOT 3/4 does and to the best of my knowledge DOT 5 is not flammable unlike DOT 3/4. These are other considerations they must take into account.
Life is full of decisions like that.


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