Re: Hydroscopic brake fluid absorbs water from the air no matter if running or not

Took my car in for the 2-year service today, part of which is replacing the brake fluid. I want to preserve my warranty so I'm having it done, and I understand that the fluid absorbs water which may affect the boiling point of the fluid and thereby affect the brakes ... but my brakes see very light use. My car sits in a garage during the week and is only driven 5000 miles a year on the streets and highways on sunny days. If I'm not out on the track or going down mountains, what difference does the boiling point make? I can't think of any of my cars that ever required a brake fluid change as part of required maintenance. Judging from the internet (and what source is more reliable than that?), some people say you must change the fluid (http://www.aa1car.com/library/bfluid.htm) and some say it's a waste (http://autos.aol.com/article/fluid-flush-fallacy/). I'm feeling that changing it every two years for a light-duty vehicle is mainly just another profit item for the mechanic. Generally I believe that if it ain't broke, don't fix it, so I'm considering not doing it for the Porsche when I get to the 4 year mark, just waiting until the brake pads need replacing. Comments?

and the water in the brake lines damages sensors and cylinders/pistons.

I'm trying to get a Mazda running again for my son and have replaced the anti-lock cylinder and a wheel cylinder so far for north of $1k. Curiously A/L is not a safety requirement in NC even if the car came equipped with it so it passes state inspection with the A/L light on.

Pay me now or pay me later question if you guess wrong on the change interval and things rust on you.

I also thought that over time, the fluid degrades on its own, not just simply with use, particularly the more performance based brands. If you do track events, there's a better kind of fluid, but it degrades quicker and has to be changed yearly. Could be wrong on the time factor being an issue, but for the biggest saftey feature on a car, it's not worth risking, especially for the price. With the proper equipment, you can bleed and change the brake fluid yourself and save money. Now that you've changed it once under warranty, the next time it has to be done will be after the warranty period expires, so no worries there on doing it yourself. I don't do it myself (again, playing with the biggest safety component of a car is not something i want to rely on my skills to perserve), but from posts on the board it seems easy enough with proper tools/equipment.

I feel that the reason that I have a Porsche is because of how great it feels while driving it, and the fact that I can count on the acceleration, steering and brakes. Maybe the top will get stuck or the radio won't work or a headlight will fail, but the things that I really need to work - brakes and tires - are the things that I keep a close watch on. I do my own pads and rotors, my own plugs and air filter replacements, and keep the scheduled maintenance cost down that way. But I have always had brake fluid changed by someone with the proper tools and experience - I have not sprung for the proper tools, and I can just see myself getting some air in the system.

Quote
TheFarmer
I feel that the reason that I have a Porsche is because of how great it feels while driving it, and the fact that I can count on the acceleration, steering and brakes. Maybe the top will get stuck or the radio won't work or a headlight will fail, but the things that I really need to work - brakes and tires - are the things that I keep a close watch on. I do my own pads and rotors, my own plugs and air filter replacements, and keep the scheduled maintenance cost down that way. But I have always had brake fluid changed by someone with the proper tools and experience - I have not sprung for the proper tools, and I can just see myself getting some air in the system.

It's OK if you don't feel comfortable doing it, but flushing brake fluid in a Porsche is really easy with a Motive Power Bleeder--while it was written long ago, Trygve's DIY instructions are still good. If you can do pads and rotors, you can do the brake fluid too.

Trygve's Boxster Brake Flush Instructions

Current Porsche: PCA Club Coupe 2 of 50

Past: 02 986 S

01 996 Turbo

00 Millenium Coupe

99 996 C2

99 Boxster

"If your factory manual calls for it, by all means, change your brake fluid."

"Bart, with $10,000, we'd be millionaires! We could buy all kinds of useful things like...love!"

Back in the day, as my cars aged, I had to rebuild many a wheel cylinders and calipers because of water damage inside the brake system. Since I started flushing the brake fluid on all my cars, I have never had a hydraulic brake part failure again. Started doing it yearly on all my cars, regardless of age or miles, in 1988, so it has been a long time. With the Box, I went with the manual recommendation of every 2 years, and that has worked out fine. I flush the system myself, so there is not much real cost to me.

Oh, and clutches too.

flush until either color is the same as what's in the container, otherwise there's some old stuff mixed in, diluting the new fluid. A bit of the new stuff in a separate glass jar will act as the reference.

As others have alluded to, if you keep a car long enough and don't change the brake fluid, you will be replacing expensive brake system parts. Not to shock you but an ABS pump (I had one replaced under warranty in my 01 Turbo) is a $5,000 part.

Brake fluid in all cars should be changed, regularly. The problem with waiting too long is the moisture starts corrosion and when you do change the fluid, it can KO the master cylinder. So it is one of those things that it is better to change it every two years as recommended, than to wait several years to change it when you notice a problem like soft brake pedal. By then it may be too late.

I bought a 67 Corvette last year, and the prior owner (foolishly) used DOT 3 fluid which is good for one year or so, vs. DOT 4 and had last changed it 5 years ago. The brakes where really weak when I got the car. I flushed the brake fluid and it literally killed the master cylinder (which was not that old)--meaning the brake pedal went straight to the floor. So I had to replace the master cylinder. If the prior owner had done what I do (which is change brake fluid every two years in all my cars) that master cylinder would likely still be good. Not expensive (a generic master cylinder is about $50), but the brakes when I got the car were really scary--I darn near blew a red light trying to stop from 50 mph (and I didn't wait until the last minute to start braking, either).

As for changing your own fluid, I would counsel against ATE blue--it stains everything blue. The first time you do a flush, just buy two liters of brake fluid, and watch the color of the old gold vs. the new ATE gold. You can see the gold change color--even if you don't, flush about 8 oz of fluid from each caliper (hence the 2 liters of brake fluid to give you plenty of fluid so you don't have to worry about running dry), and you'll have all the fluid out. And in the process you won't get the "blues"--that ATE blue tints the clear plastic reservoir on the brake master cylinder, the hoses (if you use a Motive power bleeder) on the power bleeder, and your drain hose attached to the bleeder screws. Hate the stuff.

At one time, ATE Blue had a higher wet point than Gold, but now it is the same as the ATE Type 200 (e.g., ATE Gold). Just go for the Gold, and forget the Blue

Current Porsche: PCA Club Coupe 2 of 50

Past: 02 986 S

01 996 Turbo

00 Millenium Coupe

99 996 C2

99 Boxster



Edited 1 time(s). Last edit at 04/09/2011 12:42PM by Paul S.. (view changes)

Saves a bit of time and a dram or two of material, along with the confirmation of completion.

I am with you paulwdenton, if you car does not see lots of driving time, no track time and you mentioned driving down mountains so I assume that you are living in low humidity state and not a high humidity state like Florida, I see no harm in extending the interval to 3 years or so.
Also like db996 said, this is an easy do it yourself job if you are so inclined and can be done for $12 worth of break fluid and a bleeder for $50 that you only have to buy once or borrow from a fellow PCA member.

i just did the Jetta's brake fluid change, and it's a 2002. Owned since new. Was pretty easy with the Motive. Briefly heated the bleed screw with a torch and then liquid wrenched it. Got a very firm pedal

Unlike my '03 CRV - I broke the 1st bleed screw I tried to open . Still trying to get all the air out of the new caliper. . Have a pretty soft pedal

The old brake fluid looked pretty good.

I'm changing the fluid this spring on the Boxster, only cause I got the Motive, and hoping to do a trackday again this spring. There is a date written in china marker on the master cylinder.... something 2007, so I am due, even by my stingy standards.

P

I inherited my parents' 1997 Toyota Camry and since it only had 68,000 miles and I knew it was meticulously cared for, I decided to spruce it up and check it out mechanically to use as a daily driver. I have all the maintenance records for this car since it was new; all work has been done through their Toyota dealer, and there was no record of ANY prior brake work although the brakes work just fine. Nevertheless, I took it to my local Toyota dealer for an oil change and safety inspection, and asked them to check and replace the brake pads and change the brake fluid. The service manager reported that the brake pads don't need replacing (about half worn), which says something about the way old people drive, doesn't it? He also told me that changing the brake fluid was not required nor did he recommend it as long as it was full and not causing any problems (I checked the owner's manual and indeed, changing the fluid is not even mentioned). Believe the service manager's term was, "leave well enough alone" which pretty much accords with my own philosophy. I have to say I'm surprised that a dealership would throw away a softball opportunity to sell parts and service, but they did. I just find it really weird that Toyota thinks it's okay for me to drive on 14-year-old brake fluid but Porsche thinks I have to replace it every 2 years come hell or high water.

Have to agree...it has been 10 years, have replaced the pads three times, changed the rotors, but have never replaced the fluids. We check the levels every year, but really never felt the need to change the fluids.

The car is a daily drive (sun, rain, or snow in Boston), garaged outside with a cover, and has performed flawlessly since 2000. These cars are not as fussy as many are led to believe.



Edited 1 time(s). Last edit at 04/20/2011 09:41AM by RainyDayGarage. (view changes)

... won't change as you are not consuming it and it's a closed loop.
The reason why it should be replaced every couple of years is because of the type of fluid used.
It is extremely water absorbent. It takes in water through the pores in the brake lines.
Once the water is in the fluid it can damage the pistons in the calipers and can cause other problems including brake fade.
Below is the link to a short article I wrote recently on the issue.
Happy Boxstering,
Pedro


[www.pedrosgarage.com]

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

In my limited experience, changing brake fluids sometimes can lead to other problems that weren't there normally on a daily driver.

Personal example. 2003 Honda CRV - wife's vehicle. Changing the brake fluid let to snapping off the bleeder screw from corrosion. No issues with the caliper related to brake fluid before the snap. Spent a weekend installing, bleeding and rebleeding a new remanufactured caliper. Brake pedal feel was 'fine' before the fiasco. We tow a light trailer over fairly flat terrain (most of Ontario is flat). So brakes aren't a big issue. I will likely bleed the 4 one more time, as I am not totally happy with the feel.

I have had one caliper go (stuck) piston a few years back - replaced that caliper. Most times on my Hondas it's the slides that need servicing.

If you live in Colorado, or the Smokeys, and need a lot of brakes for extended periods of time, then it would be good advice to change out the fluid. Normal every day driving, shouldn't be a problem with brake fluid. Escpecially spec DOT 3/4 stuff. The racing fancy fluids that a lot of people here use are my hydroscopic, and absorb water quicker than standard DOT 4, in an effort to engineer something with a higher dry BP, they have a short service life. Stock spec synthetic DOT4 has a decent high BP, and isn't quite the water sponge as the stuff marketed for racers.

I tracked my Boxster last year with 3yr old brake fluid in it. No issues at all on an open track. Was hammering the brakes multiple times during a 2 minute lap, including the end of the front straight (being a wus I was only going from 170'ish to 120ish km/h). No issues with fade, despite 20-30 minutes of continuous track time.

Your granny Camry is no where near going to see that degree of braking.

I plan to do a fluid change on my Boxster S brakes this spring, got the Motive bleeder.

Our 07 RAV 4 owners manual similarly makes no reference to brake fluid changes. I asked about this the last time I had the oil changed and they said it typically isn't done until a brake job (pads and rotors) is done. At 55K and still have about 1/3 of the pads left, I'll probably have this done at the next oil change just on principle.
Wed don't use the brakes a lot due to mostly highway driving but I'd hate for the calipers/ABS system to get buggered up by moisture just to save a few $'s.

It was a seldom used low mileage car still on it's first set of brake pads. I'm convinced from personal experience.

Got the granny Camry out tonight and went down a quiet street with no houses or anything on it, went up to 30 mph and slammed on the brakes. ABS worked just fine, and car stopped quickly in a straight line (it's no Cayman, but not bad for what it is). Went home, checked the brake fluid, and it's both crystal clear and has a bright yellow tint. Isn't that the way it's supposed to look when new? Isn't this stuff supposed to turn cloudy and dirty looking when it's old? I am beginning to think maybe somebody actually did change the fluid before. In all other respects the car is in outstanding mechanical condition, so maybe Dad did do the brake fluid change and just didn't keep the record.

the problem with water in brake fluid is that as your brake pads get hot from stopping the car, so do the calipers where the brake fluid is in the piston. so when your calipers heat up, so does the brake fluid and any water in it. As the water heats up, it turns to vapor. Liquids, including water, cannot be compressed. Vapor can. so when you press the brake pedal, there is sponginess from compressing the water vapor instead of pushing the brake fluid. Of course this is not going to happen a mile from your house driving 30 MPH. It can happen driving on a freeway or especially coming down a mountain where you'll be using your brakes much more.
This is why you don't want water in your brake fluid.

--
MY 2000 S, Ocean Blue, Metropol Blue, Savanah Beige.
Bought June 2000 - Sold May 2010

Yes, if the brake fluid is that old and looks that good, it was probably changed at some point.

Again, my view on brake fluid is that, for the way most people drive, old brake fluid will work just fine 99% of the time. It's the other 1% I worry about, and given how cheap brake fluid is it just seems like the wrong place to try and pinch pennies.

As I mentioned, I spend a lot of time at the track but I also do a lot of PCA social stuff. Track guys are usually very serious about maintenance, but it always amazes me to meet folks at social events who don't even blink about dropping $3,000 for an Alcantera interior but then skimp on regular oil changes.

Anyway, look me up if you're in town. I meant it about lunch.

1998 986 Turbo-Look Cab
172,000 Miles
Dilithium Crystal Supercharger

... premature failures. So changes are also an investment in fewer major repairs later. Of course, statistics mean that each individual may win or lose.

Grant

Brake fluid is hygroscopic, and even a small amount of water (1%) can reduce your wet boiling point by 10-20% - particularly if you are using DOT3 street fluid. If you are using street fluid, this means at 2 years that your boiling point can be below 200 degrees - a temperature that can be easily reached in even light driving (see the attached chart at Why Change Brake Fluid?). So you could just be doing some highway driving in heavy traffic, come to the stop sign at the end of the off-ramp, hit the brake pedal and - bang - you have no brakes. You will sail right through the intersection, because your fluid has boiled and air compresses while brake fluid does not.

In addition, if you drive in a place where it rains or snows and think you might ever need ABS, change the fluid. Brake fluid is a type of mineral oil. As such, the components in the brake system are designed to resist corrosion from mineral oil - but corrode very easily when exposed to even small amounts of water. I would be careful with that Camry as I'll bet you lunch that with 68,000 mile brake fluid the ABS in the car doesn't work anymore because the vales are rusted shut.

I have done a lot of DE and racing and have been in cars when brakes failed. Not fun. Are your brakes going to fail? Probably not. But if they do, you are screwed. And a brake fluid flush from a good independent is less than $100. And if you do it yourself, a can of brake fluid is $10. IMHO, my life is worth more than $10. There are much better ways to save money on maintenance - don't have the car detailed as often, don't mess around with iPod upgrades, don't buy new mats - none of these items will put my life at risk.

As for different opinions, people are entitled to them, but all you have to do is look at the data as to how the wet boiling point changes over time (which has nothing to do with mileage - the fluid absorbs water sitting there) and I think the argument for a regular fluid flush is clear.

1998 986 Turbo-Look Cab
172,000 Miles
Dilithium Crystal Supercharger

A few years ago I picked up my X5 from a service. BMW also recommends a two year interval for brake fluid flushing. As usual, I take a look around the car and in the engine compartment. I looked at the cap on the brake fluid reservoir and it was dusty. First, one should clean the cap before opening it and second, if you open it, you will leave marks in the dust. The service book was stamped for the brake fluid flush.
So I went to the auto club garage (TCS in Switzerland) and had them take a sample and test it. The boiling point was very low, e.g. there was a lot of water in the fluid. It was still above the legal minimum but would have gone below it in about six months. On a side note, insurance companies will check the technical functioning of your car if you have an accident and can withhold some or all of any payment if they find deficiencies like old brake fluid since that is considered negligence on the owner's part but i digress…
If you can find a garage with a brake fluid tester, go check it out. if it's okay, then there's no need to flush. But once it gets past the minimum, I would definitely change it. I'd be very curious to see what the boiling point of 14 year old brake fluid is.
I find it interesting that the owner's manuals of other cars don't mention brake fluid change. Maybe they do it as part of the maintenance but just don't mention it to the end user? But as everyone here has said, there are two critical reasons to change the brake fluid: damage to the system and poor performance under heavy use. I personally would never skimp on the systems that keep my car on the road, shiny side up.

--
MY 2000 S, Ocean Blue, Metropol Blue, Savanah Beige.
Bought June 2000 - Sold May 2010

Any water in the system would contribute to corrosion and eventual failure.

Not dust but nail polish: I had instructed a Honda dealer to check my CRX's valve clearances. Having had problems with their work before, I put a discrete dot of nail polish at the gap of each valve cover bolt. When I went to get the car, I inspected the bolts before paying, and they hadn't been touched. In front of staff and other customers I distinctly told the service manager that he was an a-hole, and always would be, and that he'd now lost my service business and any future sales or recommendations to others. I had a spare key with me in anticipation of the occasion, and simply walked out to the lot, got in my car and drove away.

then again, you're hardly using the car you bought!

Note, over time BP falls a LOT - depends on which fluid and how much water is absorbed, but 50% is not out of line.

Grant