Technical DOT 3 brake fluid wheel cylinder has some rusty mud under boots

It's been 5 years since I rebuilt wheel cylinders and new master cylinder on my 42 Olds Ute with DOT 3 brake fluid. Pulled the brake drums off rear wheel cylinder and once again I have some rusty mud under the wheel cylinder boots.
Fluid looks fairly clean, a little black tint but not brown.
Running factory drums all round.

My 42 is stored in a non heated garage here in the humid south. I only put about 300 to 500 miles per year.

I changed from the expensive original 1" master cylinder to an inexpensive 60's AMC and Jeep dual master cylinder 5 yrs ago. Works great.

Not my first rodeo but is everyone having the same problem after about 5 years ??

I have DOT 5 in my 41 Olds that I bought from my friends widow. It has a good stiff pedal, but my experience trying DOT 5 is always spongy pedal. The 41 hydraulic parts are in perfect condition after many years with DOT 5
.

 

What you described is normal with DOT 3 fluid. The cure is DOT 5 silicone fluid. You won't be sorry!

Edit, BTW, that is a really cool car! Is it factory built?

 

I'd say what you are seeing is fully normal with any car with Dot 3 that doesn't get driven.
I'm not a fan of Dot 5 but for a show car or museum that never gets driven it might be a better choice.

 

Dot 5 brake fluid has it's problems.
I worked at a spe******t brake repair shop for some years. Sure saw some strange crud come out of worn cylinders.
Clean everything and replace all seals, hoses, even the piping and it is still possible to have issues.
Count the number of oe manufacturers that use it - I think one at last count. There is a message there.
Some users love this product with a p***ion. I, for one, would not consider using this in any of my cars.

 

Dot 3 and 4 are hygroscopic. They absorb water. That's why you are finding the results you have. Dot 5 doesn't absorb but moisture will still get in the system. I have a friend who uses 5 in his pull trailer hydraulic brake system. The moisture has destroyed the parts quicker than dot 3 would have. The corrosion factor seemed to be accelerated by the separation of moisture in the system.

 

I have had DOT 5 in my T since 2000 when I finished it , I have flushed the system twice . The car has 50k miles on it ., it sits 6 months a year . I have , so far , not seen any contamination in the fluid nor have I had any brake problems . The garage is heated , however at certain times of the year it is very humid . I think that much of the negative commentary is mostly rumor .

 

the message is that manufacturers are too cheap to use the good stuff.
I worked on cars before 1967 but got serious when I got my 47 Mercury in 1967. I do have many old cars, all made before 1960 but mostly cars from the 30s and 50s. All had corroded wheel cylinders and that nasty mud. I began using DOT5 about 40 years ago and still have all of those cars and drive them all. Very very rarely does a wheel cylinder leak but when it does honing and new rubber fixes it. No more corrosion! no more nasty mud-looking stuff!

 

Just flush it every year or 2 dot 3-4 fluid is perfectly fine.

there is a reason most car manufacturers use dot 4 or super dot 4 fluid and recommended fluid changes every 2 years.

I got a moisture sensor that detects moisture in brake fluid , easy to use and an honest way to upsell flushes when I worked in automotive.

If your fluid is dark and murky you need to flush it out.

not a big deal.


And while dot 5 silicon fluid has its advantages it also has its disadvantages, so do your research before you switch.

I run super dot 4 in all my stuff.

 

I put Dot 5 in my car about 10 years ago. No troubles at all. Later I second guessed myself cuz of nay sayers and didn't use Dot 5 in my 56 F100, used Dot 3. no troubles with that either, but it's only been 3-4 years.

 

I have Dot 3 in my old rides. Never had that problem.
But I drive em a lot.
The cure is driving regularly or flushing 1-2 years
I personally prefer the driving method.

 

I don't have that problem. I live in the desert. It's great.

 

That’s a really cool car ya have.

 

Up until the time they started with ABS, Harley Davidson used DOT 5 in their bikes. Five is not compatible with ABS systems. I use five in my bikes and have never had problems. About 15 years ago, I completely rebuilt the brake system in my 55 Customline. I used five at that time, my Buddy Johnny bought the car and still has not had any trouble with it.

 

I run DOT 5 in my '31, you won't find it in a modern car with an ABS brake module, the fluid becomes aerated when the module runs to prevent wheel lock up during a panic stop. I also did not pump the brakes when bleeding DOT 5, just cracked the bleeder and pushed the pedal SLOWLY to the floor, takes longer but less of a chance of agitating all of the microscopic air bubbles in the fluid into a bigger problematic air bubble.

 

Vacuum bleeder also works well .

 

I have been using dot 5 for 40 years. I live in Minnesota, humid in the summer, cold in the winter. I have 25 old cars at this point, so some of them sit for years neglected. The ones with dot 5 AWAYS have brakes, never an issue. My Olds got dot 5 in 81, drove thru 87, sat for 23 years, dug it out and drove it on power tour 2011 with no brake issue. My F100 got dot 5 in 91, got driven for 3 months, and has not been driven since. But the brakes are still there. In 2003 I put Wilwood discs in my race car. Wilwood warned against using dot 5. I called them up and they gave me the same spiel all the anti dot 5 people are still using. Because of my past experience, I put dot 5 fluid in it anyway. It is still in there, it has never been changed or flushed and it still works perfectly. Now wilwood approves dot 5 and even sells their own line of it. The fluid didn't change, they just became educated. I could go on and on. Any of my cars with dot 3 ALWAYS fail with three or more years of sitting.
I only have 1 car that I will never use dot 5 in. ( It has mechanical brakes)
I don't care what fluid anyone else uses. It's their car, their time, their money, their safety. But I know what I'll always use.

 

The only dot 5 issue I’ve ever had was hydraulic slave cyls and throw out bearings.
Jokers leaked ever time.
Replaced em and used dot 3 and they stopped leaking.
Used dot 5 with brakes and never had an issue.
Who knows.

 

Side note re Wilwood Dot 5...........Wilwood does not recommend using DOT 5 fluid in any racing applications.

 

Used dot 5 with Wilwood big inch brakes.
Autocross car.
Never an issue.
I’d love to hear from their technical folks for not using it.

 

The corporate bean counters " heard" it was bad , they told the corporate lawyers , the lawyers told management to not recommend it ( just a theory LOL )

 

I believe the concern is that silicone base tends to foam with agitation such as on/off cycling.
I doubt if you'd notice this in a 1 minute autocross run, but endurance- road might be a different
story. Personally we've had good performance w/ Motul 5.1

 

With dot 3 you need to flush the entire system every 3 years if the car is not driven. I work for a private collection, and we have been going through the whole collection fixing gas tanks and brakes. Some of the cars have been sitting for 20 years. Bad wheel cylinders, master cylinder and the gas tanks need to be cleaned and coated. Most of the br*** floats for the sending units have dissolved with the ****py gas we have now. With Dot 5 you have to make sure no one EVER puts dot 3 or 4 in with the Dot 5 or it will turn to mud.

 

Them newfangled juice brakes are just a fad. Mechanical brakes never have this problem.

"The Security Of Steel - From Pedal To Wheel!"

 

Shnit man , most new cars don’t even have a mechanical connection on the steering colounm anymore !!

 

No that was the result of buying a new plasma cutter.

 

My fluid is not rusty, just a little dark. It's the brown mud between the piston and rubber boot that irks me, I'm afraid the wheel cylinder will rust stuck soon and no brakes !

 

you could overhaul the wheel cylinders and bleed with new fluid, and then you won't have to worry about it. If you decide to change to the other type of fluid, you might want to rebuild all the hydraulic parts.

 

when DOT3 absorbs water, you have acid in there. your brown mud is a result of the acid and it is eating holes in your cylinders. little tiny rust holes

 

Take one of the bad wheel cylinders off and take it apart. Then you will see what is going on. If not pitted you could clean them up and put kits in them. Just bleed all the fluid out with new fluid every few years and should last a long time. When the fluid starts to gets dark it's time to replace it.

 

Could the mud your seeing be brake dusst either mixing with moisture or a bit of brake fluid getting past the cups ?