Changing Brake fluid

[hdmax(mike)]

What are your thoughts on the life expectancy of brake fluid? I have heard mixed reviews on it. Some say it never needs changed and others say change it.

I have drivin more then 1,200,000 miles over the years and have never changed the brake fluid. And never have had a major brake failure. So I say let it alone. But would like your opinions.

[bryantch]

Mike,

I cant speak to the life expectancy of the fluid from the factory, however I know from track experience that old fluid will absorb water and severly lower the boiling temp. This (water) will cause corrosion within the system and can cause brake failure under severe braking conditions. I found the later out the hard way this fall while at the track in my wifes 911. I had neglected to change the fluid before we left (it was fine 60 days before at another track) and found out the true meaning of brake fade... at 120+mph heading for a 90 degree right...foot to the floor! I was able to negotiate the corner and slow the car by pumping the brakes and downshifting. Needless to say I slowed down and took it to the paddock.

Other than the problem of corrosion in the system (long term) the only way a truck would experience similar heat would be during extended braking, probably loaded and downhill.

Except for the Porsche I have never changed the fluid in any other vehicle...and dont expect to have to in my truck.

Just my opinion...

[hdmax(mike)]

Thanks Bryan!

[ 12-25-2002: Message edited by: hdmax(mike) ]</p>

[DonG]

When I was over at my local GMC delear last week for my wife's Subaru LOF, they had two samples of brake fluid on the counter. One was new and clear almost, the other was dark, dirty, and looked well used. When I asked about them, they said Subaru had started a program to change brake fluid at 30,000 miles.

GM has no such program but they said in their experience, the GM cars had just as dirty brake fluid as their sample, and they were personally recommending changing after 30,000 miles also.

They might have been trying to drum up more work, but this shop has been very good over the years, and the sample of the used brake fluid looked pretty bad.

Don

[srubrn]

On a 74 Toyota Landcruiser I used to have. I found out the hard way about changing brake fluid. I had to replace eight wheel cylinders due to water corrosion. Each wheel had two and they were $60 a piece. I now change my brake fluid on all my vehicles every two years. It's easy and cheap!!!

[mdrag]

Every 2 years seems to be the most commonly recommended interval for flushing the brake system. Here is a post I made a little over 1 month ago:

http://forum.62-65-dieselpage.com/cg...=7&t=004260&p=

With less than 10K miles on the truck and about 1.5 years old when I flushed the brake system, the brake fluid was dirty. There was a noticable improvement in brake feel/response.

[hdmax(mike)]

mdrag;
Where did you get the vacuum brake bleeder system? That sounds like it would make life very easy when it comes to changing brake fluid.

[chuntag95]

As with all fluids, what you put in makes all the difference. There are better brake fluids available that last longer or absorb moisture slower. I use ATE Super Blue or Gold. Same stuff, just different colors so you know when it's new fluid is in the system. Racers use it. I started using it after talking to a friend of mine that races since people like Merc Benz, Porche, etc use it in their cars and recommend a 3 year change frequency. All brake fluids except the silicone based (don't use unless your system is designed for it) will absorb moisture and that makes it easier for the brake fluid to boil. Then you have gas instead of liquid in your calipers and gas compresses easier than fluid and you no stoppy! This stuff's "wet" boiling point is higher than some of the cheap stuff's dry (no moisture in it) boiling point. I also found out that it makes a huge difference in pedal feel as well.
My friend has a pressure bleeder and we do all of out combined 6 vehicles on a regular basis. The only drawback it that the blue will turn the plastic to a light blue tint and it is hard to find sometimes. I actually get it at a Porsche place.
Just a question, can everyone else put the brake pedal to the floor when your really mash on it? In an emergency brake, I actually hit the floor of the truck. I have been thinking about taking it in, but I have found no leaks and "normal" stops are okay.

[Maverick]

I had my brake fluid changed in my 3500 about 3 months ago. Also had a new master cylinder put in too. This was around year and a half old mark with 90K or so miles. Old fluid was black and brake response is much better now. I had the dealer do everything.

[ 12-26-2002: Message edited by: Maverick ]</p>

[JimWilson]

I have mine changed every 50K, which for me is less then 2 years.

[mdrag]

hdmax,

I'd been using a vacuum bleedimg attachment for a Mityvac hand vacuum pump for a few years and it worked well. Recently I bought a Vacula vacuum bleeder that works off compressed air, with a container to fit on the master cylinder to maintain the fluid level while bleeding. There are also pressure type bleeders. I don't know which is better or worse...

Check out www.toolsource.com Look under the BRAKE SYSTEM category for bleeders and you'll find a large selection to give you an idea of what is available.

mdrag

[JohnM]

I change the brake fluid and flush the system about every two years and if I weren't so lazy I would change/flush it annually.

My disclaimer: I am not a chemist but did spend an intense two weeks reading about and studying brake fluids for another board about two years ago. Here is what I found: All REGULAR automotive and truck brake SYSTEMS will absorb water in the form of humidity. This humidity will even be absorbed thru the vehicle's flexible rubber brake lines. As Chris and others have said, this water has a lower boiling point than brake fluid and in hard braking situations will seriously diminish the effectiveness of the vehicle's braking system. In many/most racing cars brake fluid is changed after or just before each race so the water absorption is a non-isssue.

Chris also mentioned not using DOT 5 fluid unless the vehicle's system is designed for it. I'd like to add a little more to what Chris has said about the compatability of DOT 3, DOT 4, and Dot 5 brake fluids. DOT 3 and DOT 4 brake fluids have a glycol chemical base and they both absorb water although DOT 4 fluid absorbs less than DOT 3 fluid. When these two brake fluids absorb water the water mixes with the brake fluid and disperses itself evenly throughout the system(including the master cylinder and wheel cylinders which are usually made of cast iron. This water, which once was harmless humidity outside the brake system now reacts with the iron within the system and forms iron oxide-rust). DOT 3 and DOT 4 brake fluids can be mixed together and used in the same brake system without damage to the system because they have the same chemical base.

DOT 5 brake fluid has a different chemical base(silicone) and it handles water differently. The automotive or truck brake SYSTEM which uses DOT 5 brake fluid will still absorb water in the form of humidity but the water will not be absorbed by the brake fluid. Instead, the water, which is heavier than brake fluid, will tend to pool-up in the lowest parts of the brake system. These lowest parts of the brake system are usually the steel brake lines beneath the vehicle. If the brake lines are standard steel(not stainless) brake lines this water will eventually rust the lines from the inside and this internal damage will not be noticed until a leak develops at that low point.

Now, let's talk about the brake fluid compatability issue. I mentioned above that DOT 3 and DOT 4 brake fluids can be mixed without damage because they have the same chemical base. However, DO NOT MIX DOT 5 BRAKE FLUID WITH EITHER DOT 3 OR DOT 4 BRAKE FLUIDS BECAUSE THEY HAVE DIFFERENT CHEMICAL BASES. If DOT 5 brake fluid is mixed with either DOT 3 or DOT 4 brake fluid OR EVEN COMES IN CONTACT WITH RUBBER COMPONENTS which were formerly exposed to DOT 3 or DOT 4 fluids, those rubber components will tend to harden and crack over time and cause serious damage to the brake system.

If DOT 3 or DOT 4 brake fluid is installed on a brand new brake system, one should continue to use only these two fluids in that system for the life of that system. If DOT 5 is originally installed in a new brake system, only DOT 5 fluid should be used within that system for the life of that original system.
The subject of brake fluids is certainly much more complicated than my simple explanation.
There is no pride of authorship in any of the above, so, if any chemists or knowledgeable technicians find fault with anything I have reported, please feel free to correct my statements.

I suspect that some readers on this board, as did readers on the other board, will say that they recently filled their vehicle's brake system with DOT 5 brake fluid and everything works perfectly. I can't and won't dispute that. My statement said "... will tend to harden and crack over time...".

I hope this report provided some small additional insights to the subject of brake fluids.

Best Wishes,

JohnM
Member #2049

[ 12-30-2002: Message edited by: JohnM ]</p>

[bryantch]

JohnM,

That was probably the best explanation of the differences/compatibility of the different brake fluids I have seen...Thank you.

[JohnM]

bryantch, thanks for the kudos. Helping others is a win-win situation for everybody.

Chris, I certainly do not know why the brake pedal goes all the way to the floor during emergency stopping situations. That does not seem normal or safe. Here is a site which might give you some diagnostic ideas. Don't let the name of the site prevent you from reading the very helpful info.

http://www.fordfestiva.com/service/d...kefluid101.htm

Best wishes to all for a happy, prosperous and safe New Year.

JohnM

[ 12-29-2002: Message edited by: JohnM ]</p>

[EXPSD]

Just had the brake fluid changed in my 2000 Bonnie and after reading this I checked it and it is green not clear. Was I had?

[Stephen1]

Change about every two years in street vehicles. Every couple of months on the race car.

Steve

[Jim Brzozowski]

Ditto what JohnM said, he obviously did his homework, as I did also, when you know you can win a race by outbraking someone in a certain corner on the race track, you tend to learn as much as you possibly can about brake fluid & systems. Personally for a street driven vehicle, 2 years it probably good for changing out the fluid and flushing the system. If you can't get that done, at the least once a year, suck out the brake fluid from the master cylinder and put new fluid from an unopened container. I'm sticking with DOT 3 because its all I need, like you said they all absorbe moisture and its just a matter of time before it becomes a braking problem. I once drove for a guy that tore down every caliper and cleaned everything and replaced every oring before he would go to the track. I once say him fly off the end of the entrance to turn 1 of the road course at Daytona and I knew never to ask him why he went to so much trouble.