DOT 3 Brake Fluid - Some of us old-timers don't know the dangers

[Guest simplyconnected]

This is one of those subjects where everyone is an expert. You know, like oil changes, etc. For us Snow Birds, cold weather is approaching fast, and now is the time to winterize.

I'm really troubled that some very senior AACA mechanics don't know how dangerous DOT-3 brake fluid can get by just sitting in a closed brake system, or by opening the reservoir cap on a rainy day. You're going to think I'm nuts, but SOME brands of brake fluid can pick up moisture through the opened plastic container. ABS systems can freeze up here in the north... read on.

Here's a quote from AutoZone:

"Most brake fluid is hydroscopic: It absorbs water. On the positive side, any moisture that enters the system—through condensation, through rubber parts such as seals and hoses or through an unsealed bottle of brake fluid—is dispersed throughout the fluid. That way, chances of localized corrosion and fluid freezing are minimized. On the other hand, absorbed moisture lowers the fluid's boiling point, raises its freezing point and degrades its anti-corrosion additives. As little as 3% moisture can decrease fluid's performance by 30% and also negate its anti-corrosives. Additionally, standard DOT 3 brake fluid can only absorb up to 7% moisture, after which water droplets—and braking problems—begin to form. Anti-lock brake systems (ABS) are especially affected by moisture because they can cycle as many as 20 times per second. Spongy pedal feel is a sign of moisture in the brake fluid.

Depending on temperature fluctuations and humidity, a brake system can take on as much as 3% water in as little as eight months. It's usually recommended that the fluid be entirely flushed at least every two years or 24,000 miles."

Here's the link: http://www.advanceautoparts.com/english/youcan/asp/ccr/ccr20011001bb.asp

Now I find, not all DOT-3 Fluids are created equal. Some are much more resistant to moisture absorbsion, but they cost an arm and a leg.

Check THIS out:

"As water content in brake fluid increases over time, the boiling point decreases. Fluid with a reduced boiling point (or high water content) can create vapor by boiling in the caliper, or wheel cylinder. <span style="font-weight: bold">The result is sudden brake failure. And water in the brake fluid can contribute to corrosion of parts such as steel pistons and ABS modulators.</span>

The end result is even though DOT 3 fluid is "rated" at greater than 401*F, in the typical 3 to 4 year old car with 3 to 4% moisture content, it could boil under 300*F. And if it has got more than 4% moisture, you may as well be running straight water!"

Here's the link:

http://www.shotimes.com/SHO3brakefluid.html

Am I barking at the moon? I hope not. For a few bucks, I'm changing all my cars' DOT-3. If the bleeder valves break, I'll drill them out and install new, but I'm changing brake fluid every two years from now on. It's cheap insurance.

[Guest NEMO]

As you said it only holds a cup or two,and you bleed with out taking the wheels off.These are your words.

[Barney Eaton]

At the 2001 BCA national meet in Buffalo, I did a poorly attended tech session on this subject. We were loaned a device (made by a company in Buffalo) that measured the moisture content of brake fluid. Most of the Reattas we checked were in the 3-4% range....the reading on the device only went to 7%.

We did test a 1960 Buick that was entered in the show that pegged the meter.

On the amount of water DOT-3 can absorb... I cannot find anything in print that specifies the max. I had one "expert" tell me that brake fluid, like antifreeze will absorb all the water you add to it.

There have been several testimonials on this discussion page of owners that have changed their old fluid and their brake problems "went away".

Changing or Flushing the fluid on our cars is cheap preventive maintanence. The hydraulic pump on the Teves system does not like dirty fluid. Reatta owners should flush their brake fluid every 2-3 years if they live in most places......in a dry climate, you can go longer.

[Guest simplyconnected]

Barney, I was hunting the net for more about the 7% max absorption, when I found a DOT3 Refractometer (which is what you used in Buffalo). Offered by MISCO Refractometer for the bargain-basement price of $435.00, this one only goes up to 6%, and probably isn't as good as the one you used. (Four hundred bucks buys a whole lot of brake fluid.)

More importantly, I found something I never thought of: Many hydraulic clutch pedals use brake fluid, in cars, motor homes & RV's, hot rods, etc. One site claimed, even though the owner's manual recommends changing DOT-3 every 24K, HALF the cars in the US never get changed. And, because this recommendation didn't appear in the older owner's manuals, some garages believed it just didn't need to be done. (Maybe that's why your Buffalo meet was poorly attended.)

Every site cautions about boiling points and how critical that is. Living in Detroit, I want to know the freezing points, to benefit drivers with ABS systems.

[Guest kennyw]

A good read: Most bleeder valves are on the [top] to get the air out of the system. Almost impossible to get the fluid around the piston? You should see how this effects motorcycle disc brake systems. Let a bike set for two years and you are going to rebuild the whole system.....My newer Harley uses dot-5.....Haven't had a problem with it. The word is, that you cannot change a dot-3 system to use dot-5? Anyone out there have an answer to that one? Question: what about a reverse flush? Pump fluid through the bleeder valve back to the master cylinder and use a turkey baster to get the old fluid out. All late cars are supposed to be pressure blead, not pumped with the brake pedel? Most of us don't have a pressure bleeder system..........ken

[Ronnie]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Question: what about a reverse flush? Pump fluid through the bleeder valve back to the master cylinder and use a turkey baster to get the old fluid out.</div></div>

Ken, That might possibly be a bad idea.

Any debris like rust, metal particles and moisture tend to accumulate at the lowest point in a hydraulic system that does not make a complete loop back to the pump and reservoir. That is due to gravity.

Brake systems are the same type of hydraulic system. Fluid pushed through the lines never returns to the pump or reservoir. By pushing the fluid from the caliper, (bottom of the system), back to the reservoir would pump any sediment that has settled at the bottom back through the ABS valves and master cylinder, which might cause problems.

Just my opinion.

[Barney Eaton]

I understand there are some test strips (like litmus paper) that change colors and you can read the % of water. I have not found them locally.

It was touched on above, one scary thing about the moisture, is the lowering of the boiling point. Can you imagine having a tow vehicle that had 7% moisture trying to stop a trailer and car on a mountain grade? One graph shows the boing point being lowered 100F with 3% moisture. DOT-3 must have something like 405F boiling point when it is totally moisture free. There is also a DOT requirement that it never go below something like 240 maybe 280 but that is pretty easy to exceed.....what tempature do you think those NASCAR brakes see when the rotor is glowing?

DOT-5 (silicone) it is not suitable for cars with ABS.

The fluid will aireate (spelling)(some might call it cavitation) when the fluid is rapidly mixed. The rapid action of the ABS solenoids will cause this condition...making DOT-5 unsuitable for cars with ABS.

DOT-3 is cheap when compared to the cost of replacing brake components. CHANGE YOUR BRAKE FLUID.

[Guest Mc_Reatta]

If you hunt on good old eBay you can pick up a pressure bleeder for low cost. You only need it for the fronts. The system pump will do the rears nicely all by itself. The pressure bleeder is about the only way to bleed the master cylinder if you didn't bench bleed it before installing in the car as well.

[Guest MauiWowee]

I use a Mity-Vac. It pulls rather than pushes.

[Guest F14CRAZY]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: kennyw</div><div class="ubbcode-body">A good read: Most bleeder valves are on the [top] to get the air out of the system. Almost impossible to get the fluid around the piston? You should see how this effects motorcycle disc brake systems. Let a bike set for two years and you are going to rebuild the whole system.....My newer Harley uses dot-5.....Haven't had a problem with it. The word is, that you cannot change a dot-3 system to use dot-5? Anyone out there have an answer to that one? Question: what about a reverse flush? Pump fluid through the bleeder valve back to the master cylinder and use a turkey baster to get the old fluid out. All late cars are supposed to be pressure blead, not pumped with the brake pedel? Most of us don't have a pressure bleeder system..........ken </div></div>

I'm interested in seeing if this is possible. When I removed my calipers which I assume were original, even though I had bleed my system recently before there was some nasty fluid that drained out of them with the brake line disconnected. My concern though would be getting this junk in the ABS hydraulics.

Perhaps you can reverse bleed the calipers with the line disconnected...?

[Guest crazytrain2]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Mc_Reatta</div><div class="ubbcode-body">The pressure bleeder is about the only way to bleed the master cylinder if you didn't bench bleed it before installing in the car as well.</div></div>

Does "bench bleeding" the master cylinder apply to the Teves Mark II system as well? If so, do you have instructions on how to do this?

Thanks,

[Guest simplyconnected]

At the factory, we use vacuum for everything; A/C, coolant, brakes, and P/S. Of course, everything is void of any fluid when we start. Other than pulling pistons out, I don't know how else to clean inside cylinders. But, if you are worried about any tiny bubbles, my choice is a vacuum pump.

Start with brake fluid 1/2 filled in the M/C, and pull a vac. If all the fluid is sucked in, do it again until a level is maintained, top it off, and done.

Cooling systems are notorious for voids and air bubbles (that prevent effective flow). Same thing; fill it up and draw a vac.

Maybe I should invent a manual vacuum pump by using a long bicycle pump with the leather turned around. When you pull up, it creates a good vacuum. I gotta think about this... 1-1/2" Schedule 40 PVC might work better...

[matthewlawe]

"Maybe I should invent a manual vacuum pump by using a long bicycle pump with the leather turned around. When you pull up, it creates a good vacuum. I gotta think about this... 1-1/2" Schedule 40 PVC might work better..."

It's called a <span style="text-decoration: underline">bilge pump</span> available at marine stores.

Regards

matthewlawe

1989 White/Blue

[Guest steveskyhawk]

Before the days of tire dressing we used to take brake fluid to the tires. It sure did make them shine for awile!

[Barney Eaton]

Some air compressors will work as a vacumn pump.

(1) you need to be able to attach a line to the intake air port. Many compressors have a opening covered with some sort of filter.

(2) you must open the output or storage tank so it is not trying to compress air.

You cannot get a high vacumn but probably enough to put a vacumn on the brake resevoir and not crush it.

[Ronnie]

An old compressor out of a refrigerator will work well as a vacuum pump. It can be used on automobile A/C systems if you want to make an adapter to connect it a set of A/C gauges. I have used one before but it is very slow.

[Guest steakneggs]

Probably the only way to remove stale brake fluid from the bowels of a caliper would be to unbolt it and dump it out thru the bleeder valve. That's if you want to get all the old stuff out when flushing. Steak

[Guest simplyconnected]

I recently bought some old 1975 junk yard spindle/caliper/rotor sets for a drum-to-disk conversion. I cleaned each basic component, but was really amazed all parts were ferocious steel/iron. No stainless, anywhere. The pistons looked like hell inside, but I was able to clean them up and re-seal everything with new (for under $5 total).

Steakneggs, there's NO WAY to clean inside calipers without taking them apart. Water-saturated brake fluid causes RUST that bloats surfaces, causing pistons to stick in their bore. I finally removed the pistons using compressed air and a hammer. Kids, don't try this at home! It's easy to lose fingers.

DOT-3 inhibits rust as long as it's not saturated with water. Purging with new fluid stops rust.

Ronnie, I love your idea of using a refrigeration compressor. Some of the old party stores have big two-cylinder jobs. Reason they take so long is they are strictly HIGH PRESSURE pumps, which makes them low volume. I also discovered, I need 25-inches of mercury (Hg) for proper evacuation vacuum, then fill with FRESH DOT-3. If old DOT-3 is used, the water content WILL BOIL. THAT's why they keep talking about the boiling point of DOT-3! Under a 29-in/Hg vacuum, water boils at a 76.2*F. Cavitation cancels the vacuum, so use fresh DOT-3.

[Guest crazytrain2]

Sorry guys but with the vacuum pump are you saying to pull vacuum from the top of the reservoir (where you fill), and running a tube off of the bleeders into fresh fluid?

I sure don't want to pull old fluid through the Teves Hydraulics.

I've also bee reading that you need a Tech 1 type scantool to actuate the six (6) valves in the modulator to get rid of air pockets that might be trapped in there.

Right now I think I'm gonna buy a J-35798 (J Kent) and use my trusty little air compressor to push 20psi down through reservoir. Still wondering about this scantool thing though

Thanks

I have a name for my pain, and it's name is TEVES

[Guest steakneggs]

I was just talking about changing the fluid in the calipers as part of the flushing process. You know like the dilemma of changing the trans fluid but leaving a bunch in the torque converter. I'm just suggesting a way to get it all out, maybe every decade or so. I personally would never worry about the little bit in the caliper. Steak

[Guest NEMO]

As I stated,When you have a brake job done,a fluid change is not included,only toping off the master cylinder. The reply I recieved by the author of this post,simplyconnected stated on 8/25/08 was, oh yes it IS, and sometimes between brake jobs. He never explained his words.The flushing of the fluid is a job that takes 2,unless you use a vaccume to suck the fluid threw the bleeders,on the fronts.The rears can be done with holding the brake,and the pump will discharge the fluid out the bleeder. Keeping the master cylinder full.This is more work,then just topping off the master cylinder.

[Tinker]

Home made pressure bleeder: http://www.bmw-m.net/TechProc/bleeder.htm

A must have if you are a do it yourself-er.