Brake Fluid

[ursus]

I bought a Model A with a braking system from a 1940 Ford. The master cylinder mounting and pedal assembly is a bit dodgy so will be be reconfigured for safety's sake. The previous owner passed away and none of his heirs knows anything about the car. My question is: how does one determine what kind of brake fluid is in the system currently? Is there some kind of test for this?

[JSeery]

If it were mine, I would flush it and use new fluid that you want.

[ursus]

Originally Posted by JSeery

If it were mine, I would flush it and use new fluid that you want.

Wouldn't the flush solution be different for DOT 3 or 4 versus that used to flush out DOT 5 fluid? Or, is there some universal flush solution? Would seals and cups running in one type of fluid need to be changed out for a different type of fluid? My original plan was to simply continue using the same fluid, whatever that is.

[petehoovie]

Continue using the same fluid. DOT 5 should only be used in a brake system that has no contaminants. e.g. - a new or totally rebuilt brake system....

[JSeery]

To find out which you have already in the system:

1. Use a dropper (an eye or ear-dropper) and withdraw some fluid from the master cylinder.
2. Put it into a glass jar and then add clean water to the fluid.
3. Put the lid on the jar and shake it well.
4. Let it stand for a few minutes.
5. If the water and the fluid have mixed thoroughly and can not be separately identified, then you have regular auto brake fluid.
6. If the water and the fluid have not mixed, or have formed blobs or layers, then the fluid is Silicone.

[ursus]

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Thanks, JSeery. That is what I was looking for. It makes sense, given the tendency of DOT 3 or 4 to attract water.

[tubman]

Originally Posted by petehoovie

Continue using the same fluid. DOT 5 should only be used in a brake system that has no contaminants. e.g. - a new or totally rebuilt brake system....

This is not correct. I changed my '68 Corvette from DOT-3 to DOT-5 about 20 years ago. I thoroughly flushed the system with denatured alcohol and then filled it with DOT-5. During the ensuing 20 years, the brakes worked perfectly. BTW, the system was very difficult to get bled (I don't know if it was the fluid or the Corvette brake system), but it was the most difficult brake bleeding I have ever done.

Since then, I have gone back to DOT-4 fluid for all my cars. I have "Speed-Bleeders" on them, which makes bleeding an easy one-person job. Also, I purchased a device that allows me to test the brake fluid in a car for moisture content. As long as the moisture content of DOT-3 or DOT-4 fluid remains low, it will function perfectly. Over the years, I have found that it takes from 10 to 15 years for DOT-3 or DOT-4 to even approach the moisture level that would requires a fluid change. Think of all the old beaters out on the road that still have their original brake fluid in them.

My recommendation is to flush the system with denatured alcohol and fill it with quality DOT-4 fluid.

[Frank Miller]

I'll leave the water part alone but I have found DOT to be less corrosive to the brake system as well as paint. DOT 5 is a little more expensive but still cheaper than paint.

[JSeery]

Originally Posted by Frank Miller

I'll leave the water part alone but I have found DOT to be less corrosive to the brake system as well as paint. DOT 5 is a little more expensive but still cheaper than paint.

The water part is a lot of what the difference is, DOT 5 is less corrosive, in part, because it does not absorb moisture like DOT 3/4 does.

[Kurt in NJ]

with dot5 fluid the water lays in drops, it doesn't mix, have to take it apart to get it out
with regular fluid the water is kept in suspension, comes out with a flush

I tried dot 5 in a MG i had, made the clutch feel stickey, the rubber didn't last near as long as with regular fluid

I had a 46, 39, when the choice came to trim the fleet they got sold to end the brakes leaking,pulling because of fluid on the brakes---have the model A,36 because they have reliable mechanical brakes

[Cecil/WV]

I had a 1980 Olds that I bought when the original owner died and I got it from his widow in 1998. He put DOT 5 in it when it was new and I got it with over 200,00 miles on the clock and I ran it until 2008 and sold it to a friend for his teenager to drive to high school. at this time it had over 300,00 miles and about a year after I sold it, they had to replace a wheel cylinder that started leaking.

[JSeery]

Originally Posted by Kurt in NJ

I had a 46, 39, when the choice came to trim the fleet they got sold to end the brakes leaking,pulling because of fluid on the brakes---have the model A, 36 because they have reliable mechanical brakes

Hydraulic brakes have been around for a while, think they have most of the problems worked out now. Bad parts is not a design issue, it is a bad parts issue.

[fordv8j]

I'm using dot-5 in both our 38s,got it at NAPA, it has a purple tint to it

[Kurt in NJ]

Originally Posted by JSeery

Hydraulic brakes have been around for a while, think they have most of the problems worked out now. Bad parts is not a design issue, it is a bad parts issue.

Having a lot of issues with total brake failure on modern less than 8 year old cars, 20 years ago it was rare to replace brake pipes, perhaps 20 feet a year, now we stock over 100 feet of pipes, and use more each week, and this is not really a salt belt area, I don't think they quite have the long term reliability worked out ---

[34PKUP]

Originally Posted by Kurt in NJ

Having a lot of issues with total brake failure on modern less than 8 year old cars, 20 years ago it was rare to replace brake pipes, perhaps 20 feet a year, now we stock over 100 feet of pipes, and use more each week, and this is not really a salt belt area, I don't think they quite have the long term reliability worked out ---

If you are located in NJ it's hard to believe that you are not in the salt belt.
Vehicles travel into and out of the salt belt.
Long term reliability = Stainless steel brake lines.

[Kurt in NJ]

My brother was helping a friend with a mustang, got the stainless premade set, but couldn't stop leaks at the fittings, the flair had a rough surface where it has to seal, even with new fittings it still leaked, I made cupronickel pipes, this is what we use for replacement pipes at work, though I have found that there is a tapered lap made to smooth the flair on stainless pipes, but it won't fix the cracks in the flair, the cupronickel is soft, flairs well, no leak problems

South jersey at the coast is much different snow wise than north jersey, some years less than 6" all winter

[Frank Miller]

Originally Posted by Kurt in NJ

Having a lot of issues with total brake failure on modern less than 8 year old cars, 20 years ago it was rare to replace brake pipes, perhaps 20 feet a year, now we stock over 100 feet of pipes, and use more each week, and this is not really a salt belt area, I don't think they quite have the long term reliability worked out ---

Kurt, you're pretty knowledgeable and I have noticed new cars rust differently than old ones, at least at the chassis level. Back in the day stuff just rusted. Now the rust seem to take on a barnacle like structure that does even more damage. I am not sure what is happening to the metallurgy today but they seem to have done something to create this problem.