Brake Fluid...

[KatoKato]

If I am using my car as a daily driver why is it necessary to change the brake fluid every two years?

I realize that the fluid is hygroscopic and as it absorbs water it can cause corrosion in the brake system and will also lower the boiling temp. of the fluid. This is why I do change mine every two years.

I am asking because a mechanic friend of mine says that most cars up here don't ever have the fluid changed duing their lifetime unless it's to replace lost fluid from a compromised system.

Your thoughts would be appreciated.

Cheers,
Kato

[old man neri]

Originally Posted by KatoKato

I realize that the fluid is hygroscopic and as it absorbs water it can cause corrosion in the brake system and will also lower the boiling temp. of the fluid. This is why I do change mine every two years.

That's essentially the reason as I understand it. I know for my honda and other cars I have heard it is recommended every 4 years. For the porsche it is probably 2 years because it is more of a 'performance' oriented machine and thus could see higher brake temps.

The reason people don't do it....probably laziness and unwillingness to spend money. I personally don't like to roll my dice when it comes to my brakes.

[Head416]

It's so easy and the cost is like $30, that's cheap insurance.

[HarryD]

The moisture your brake fluid absorbs can corrode the insides of your brake system and have them stop working. For the cost of an annual flush (<$30 if you DIY) you can have reliable brakes. Seems penny wise/pound foolish to not bleed.

[Jeff Alton]

Brake fluid is cheap.

Flushing it is easy.

Oil is cheap.

Changing it is easy.

IF your mechanic told you that most cars don't have their oil changed regularily (which they don't) would you follow suit?

Ask him how much to replace a Master Cylinder and rebuild all four calipers and replace a few of the hardlines, then make your desicion.

Plus, the next time you step on the pedal hard in an emergency braking situation, do you want the car to pull to the left or right?? That could cost you a wheel, tire, a-arm etc or be the difference between hitting the car ahead or not hitting it......

Cheers

[javadog]

QUOTE=KatoKato;3658251]If I am using my car as a daily driver why is it necessary to change the brake fluid every two years? I realize that the fluid is hygroscopic and as it absorbs water it can cause corrosion in the brake system and will also lower the boiling temp. of the fluid.[/QUOTE]

Well, technically speaking it's not neccessary, just a good idea. Here's the long version. The fluid absorbs moisture form the air. A little bit, every day. This moisture will eventually corrode the inside of the master cylinder and caliper bores. When you use the brakes, if you move the master cylinder piston or a caliper piston through an area of their bore that has corrosion damage, you can damage the piston seals. Enough of this and fluid will escape past the damaged seal and your brakes won't work well. You'll probably still have some braking capability, they just won't be able to generate their full power. If it gets bad enough, you can lose all of you braking capability, although this usually happens gradually and you sense there is a problem before it gets this bad.

The other potential problem is much worse. If you get enough moisture in the system and you get the brake fluid hot enough, you can vaporise the water in the fluid which will lead to a sudden and ususally complete loss of braking ability. This is more likely on a track or when using the brakes frequently, like in a mountain descent. Either way, you won't know you have the problem until you completely lose your brakes. Then, it's too late. Hope your hand brake is well adjusted....


QUOTE=KatoKato;3658251]I am asking because a mechanic friend of mine says that most cars up here don't ever have the fluid changed duing their lifetime unless it's to replace lost fluid from a compromised system.[/QUOTE]

Most people are ignorant of the mechanical workings of a car, and cheap too. Most get away with it.

JR

[Joe Bob]

Just do it because WE say so......

[KatoKato]

Thanks JR .... That was a very well presented explanation. I will indeed keep with the two year brake fluid flush and fill plan as I always have.

Cheers,
Kato

[Thrlls]

Originally Posted by KatoKato

Thanks JR .... That was a very well presented explanation. I will indeed keep with the two year brake fluid flush and fill plan as I always have.

Cheers,
Kato

Good idea!
It's just basic maintenance, a lot like going to the doctor for a check up every 2, 5, 10 yrs. depending on age and gender. You don't have to do it, but when something is found later, it probably could have been prevented if it was found sooner.

Hence the initials PM = Preventive Maintenance...it's a good thing.

[widgeon13]

If you do not bleed the system annually there is a good chance that a piston will rust and get stuck in position, then you might have to replace the caliper, especially if you are not mechanically inclined (too freaking lazy to bleed them annually). particularly if the car sits for extended periods, over the winter. It's one of the easiest tasks to complete and gets you to know what and how the brake system works since it is one (if not the most important) system in your car. Allows you to check disc wear, so your mechanic doesn't screw you telling you that you need new rotors, check tire wear, look for rust on the undercarriage and generally examine the suspension components and last but not least, it's fun. When you do it a few times, it gets much easier.

[Thrlls]

BTW - Flushing and Bleeding are done for different purposes.
One is to replace all the old fluid in the system, and the other is to remove any air. It's good to get ATE Blue & Yellow (yellow is TYP-200?) racing fluid so you will know when the system has been flushed by the change of fluid color coming out.

[JeremyD]

like all things Porsche - you either pay now or pay later. Price out the cost of replacing calipers, hard lines, MC on your 911 + labor and then tell me it doesn't make sense to spend the $30 on yearly preventive maintenance.

[Emission]

I've seen expensive repair bills on older cars that neglected brake fluid flushes... new master cylinder, caliper rebuilds, etc... it's not cheap.

[burgermeister]

Just seems odd that any supposedly "low quality, poorly engineered" (media opinion, not mine) GM car will go for its entire lifespan without ever needing brake work other than pads and rotors .... no fluid changes, no master cyliders, no caliper rebuilds. Of course most other vehicles don't have a vent hose open to the atmosphere attached to the reservoir ...

[Gunter]

Originally Posted by KatoKato

Thanks JR .... That was a very well presented explanation. I will indeed keep with the two year brake fluid flush and fill plan as I always have.
Cheers,
Kato

Besides flushing every 2-3 years, "Exercise" the pistons in the calipers by moving/pushing the pads back and then bring them back out with the help of the brake pedal.
Do it 2-3 times, back and forth.
That prevents the pistons getting frozen (rusted) inside the calipers.
I find it easiest to do that with large channel-lock pliers.
Open the pliers and place the jaws on the edge of the steel part of the pads and the outside of the caliper right where the pin-hole is and squeeze.

BTW: I wouldn't go back to a mechanic who doesn't see any benefit in flushing the brake fluid every few years.

[jhubs]

Ok, I will buy into the "moisture-corrosion" theory for now. Please explain where the "moisture" comes from? I'm not a mechanic, but I thought the brake fluid was a "closed" system and not exposed to the outside air. I live in Colorado and there is no moisture here...ever!

[RWebb]

Actually, there is PLENTY of moisture in Colorado. A condensing condition exists whenever the temperature drops below the dew point temperature - you see this as rain storms in summer and snow or sleet, etc. in winter, + fog at various times. That means that there is SO much moisture that the air is completely saturated.

There is always moisture in the Earth's air. If you breathed really dry air or let your skin be exposed to it for a while you'd be _real_ clear on that. I and my students have produced almost completely dry air in our lab (to get a std. to mix and produce various humidities) and it is a different animal. The closest most people have come to that is winter at -40 oF or lower where your skin flakes off every week.

So... change your brake fluid - it is easy to do. You can likely do it every 2 years, not every year, unless you are a racer and hard on your brakes.

And, the brake fluid system IS open to the air.

Low quality, chopped-liver GM cars do OK (usually) b/c their drivers rarely make performance demands on the brakes.

[jhubs]

RWebb, Thanks! For 2 years I lived in Vancouver, WA across the river from Portland, "Orygun" and now THAT's Moisture!!! Ok, every 2 years, I'll do it!

Jerry

[Gunter]

Originally Posted by jhubs

Ok, I will buy into the "moisture-corrosion" theory for now. Please explain where the "moisture" comes from? I'm not a mechanic, but I thought the brake fluid was a "closed" system and not exposed to the outside air. I live in Colorado and there is no moisture here...ever!

Thank you for buying into it.
Air-moisture-content was taught in school at some point.

See that small hole in the cap on top of the reservoir?
That provides the necessary air intake to prevent a vacuum in the reservoir as the fluid level goes down when the pads wear.
Another topic taught in school going back to the days of Archimedes.

I strongly suggest that you do a search on breaks here at PP to learn more; there is a lot to it, and you'll end up knowing more about brakes than your mechanic.

Trust me, I am an old ME.

[jhubs]

Gunter,
I looked at the Plastic reservoir and noticed a rubber tube coming out the side of it. When I change my brake fluid, do clamp off that tube? Seems logical.
I'm learning more about "science" on this forum than I ever did in school.

Jerry (retired art teacher)