Why should I flush my brake fluid every year, you ask?
 

:EDIT: Mercedes Benz Factory Service Recommendation is every two years. :EDIT:

I shall give my standard lecture on brake fluid, for those who may have mercifully missed it! Ha, Ha too late! YOU MUST READ ON...

Brake fluid is hygroscopic = Means it LOVES water.
Huh? where does it get water...?

There is a tiny hole in the master cylinder cap which allows atmospheric pressure to equalize when the level drops due to pad wear. Eventually over the year, the fluid becomes diluted with water. This water can cause rust in the system, but a worse fate than that awaits!
(wait for it)

Brake fluid has a certain boiling point. DOT 3 has a lower point than the later DOT 4. (NEVER USE DOT 3) DOT 5.1 has the highest.
DOT 5 is silicone fluid and does not absorb water, and is not included in this discussion.

Okay, here is what happens. Water dilutes the fluid, right? Right.
Unfortunately, water boils at a lower temp than brake fluid, so the boiling point of the brake fluid is now lowered.
Why is this important?
In normal use, you won't notice the difference. Brake feel stays the same. Even if you were to use straight water!
The problem comes with intense use, say coming down a mountain side with sustained braking (and pulling an enormous 80 ton yacht, say).

Your calipers heat up with the attendant friction (normal). But now, because of the compromised brake fluid, the fluid starts to boil! What happens when the water in the fluid boils?
That's correct, you get STEAM!!! Steam is a gas! gas does NOT work well at all as a hydraulic medium!!!
What happens to your brakes?
NOTHING!
It is known in the trade as "brake fade". (one of several types)
No matter how hard you press on the pedal, you won't get any more brake. You will probably start to speed up as you are going down hill. The press folks call this "...he lost his brakes"

There you have it.
Change your fluid at least once every other year (in dry climates) and if you live in Louisiana or some humid place, once a year.
Pain in the butt, huh.
Your choice, but you are now informed and can now bore other people with said lecture. ;)

240 Ed:

I could not have said it better! In addition, water in brake fluid = rusting/corroding brake componets = failed brake components because of the rust/corrosion = at a minumum poor braking because componets do not move like they should (like the caliper piston not pushing on the brake pads with full force) = brake components needing R&R long before they would need to be but for not changing the brake fluid. Absorbtion of atmospheric moisture causes brake fluid to turn opaque and tells the aware owner to replace the brake fluid. I use my Mighty Vac to R&R the brake fluid every year, doing it when the humidity is low - like the M-B owners and service manuals call for.

Tom

Hygro...

I'm with ya'll on this. Every failure I have ever seen (outside of running the pad backing into the rotors, which I have really never seen) was caliper failure because of not changing the fluid.

Amen!

I have only been driving newer vehicles until lately and so I never thought much about brake fluid. When I received my Unimog it had a leaky wheel cylinder. Changed the cylinder and bled the system. The crap in the main bowl was scary! The crap that came out of the lines was UGLY!!!!!!!:eek:

Just did the front brakes on my 300CD and again, UGLY!! brake fluid that looks like swamp water. I am starting to wonder if anyone ever changes their brake fluid? (present company excluded, of course).

For all those who have not changed their brake fluid, DO IT!! It is like the old Fram commercial, you either pay me now, or pay me latter. A few bucks of fluid is alot cheaper than wheel cylinders or master cylinders. My unimog wheel cylinder was $200CDN, OUCH!

Just curious as to why I have never heard of changing brake fluid until I got into German cars. My VW calls for brake fluid change every 2 years. I mentioned changing the brake fluid to co-wprker who owns a Ford, and he said he has never done that and has had no problems.

My wife is beginning to hate this forum.
Now I have something ELSE to do on our MBs! :D

Just how does one change the brake fluid? Would I suck it out the top or is there a drain?

Does anyone use DOT 5.1? Should I stick with DOT 4.

Do you have to 'bleed' anything? If so, how?

(Boy, too many question this early in the morning...)

Thanks guys!

If water in the brake fluid is bad why did they use a hydroscopic fluid? Why not hydraulic fluid for hydraulic brakes?

Regular hydraulic fluid has a number of problems
 

if used in brakes, especially, that its flashpoint is much too low -- instead of boiling and producing brake fade on the way down Pike's Peak, it might begin to burn. Besides that, viscosity stability at an extreme temperature range is very important, and only _synthetic_ hydraulic oils might have a chance here -- but would they still be compatible with the types of seal materials needed to deal with the above problems? -- cf. the silicone DOT 5 dilemma: great in British braking systems from the 50s and 60s (including my much lamented '66 Lancia Fulvia Coupe), but bad for anything else.

Jim Anderson

That is just a super question!

I dunno...

But I think blake fluid IS hydraulic fluid. But it is different than "jack oil" used in hydraulic jacks. Hmmmm.

I am sure "they" did some research and have arrived at this stuff after much testing.

And if water is so bad why did they use sponge fluid? Did they have square pants:D

Sponge Bob
 

Is this string about Sponge Bob changing his brake fluid ?

Is this a good way to bleed?
 

do you folks think this will work for bleeding. It sounds good. any other suggestion on flushing/bleeding the brake system. I have to do that on my MB and my wife's Accord.

http://www.mityvac.com/techindex.html

MVK

ear cleaning bulb
 

Everyone has an old ear cleaner lying around. They work great for sucking brake fluid out of the reservoir. Just don't put it back in yer' ear:D

And if water is so bad why did they use sponge fluid? Did they have square pants
 

I gotta tell ya Bob, I am still working on this one...

Re: Is this a good way to bleed?
 

This works better.

http://www.motiveproducts.com/ordernow_bleeders.htm

Pulling in the wet
 

Could this be why car pulls to the right and breaking is minmal in the rain/wet?

It should not have anything to do with rain, and hydroscopic, etc.
Sounds like you have front calipers which need to be taken apart and cleaned, and perhaps new seals put in.

I would try bleeding/changing the brake fluid first. That can free up the caliper sometimes.

I think you mean Hydrophylic not Hydroscopic (hydro=water; phylic=love), but I could be wrong.

ATLD

The correct term is :
Hygroscopic

I know it looks funny but, yacht!
from Middle Low German jacht, short for jachtschip, literally, hunting ship.

Has anyone ever used that Power Bleeder? I'm embarassed to admit that I haven't bled my brakes in........ years mostly because I'm too lazy to solicit the aid of someone else to pump the brake pedal. If that kit works well, $45 seems pretty reasonable and it would promote more frequent fluid changes. Thanks.

ALex

We tried using my Mity vac to bleed the breaks on a 300sd and it didn't work so hot so if someone has done it that way please speak up as we didn't have much luck. We wound up doing it the old way. I have read some interesting info regarding bleeding the old way, and that is when the pedal is pushed beyond its normal travel you stand a good chance of damaging the master cylinder. The little "plunger" gets into a part of the cylinder that its not used to being "matted" with, Yata, yata, yata anyway thats the theory I heard.

Have also heard good stuff about that other system where you pressurize the master cylinder, one man (or woman) job.:cool:

I have never used the vacuum bleeder either, but I did pick up a clue that last time I set out to do the brake flush. Go spend a couple of bucks at the grocery store and get a turkey baster. Use that to empty the brake fluid resovoir and fill it with clean. Then start in on the flush. Speeds up the process.

Silicone Brake fluid ?
 

My old 1977 Toyota Celica once got a seized wheel cylinder. When I replaced it, I noticed that there was a rust spot, nearly round, on the inside of the cylinder, just as you would assume would be made by a drop of water trapped inside. In addition, the fluid was nearly black.

I assume that this stuff was black because it had slowly been dissolving rubber from the seals and other rubber parts, since dust would have a hard time finding its way into the master cylinder.

I had heard of silicone brake fluid and replaced the system with silicone fluid, using a Mity-Vac.

The car seemed to have a harder pedal, and stopped as well as any car with disc/drum brakes. I never had another wheel cylinder or caliper go bad after that, over 75,000 miles and 7 years.

I also replaced the fluid in my wife's 1980 Toyota Corona. Again, I never had another brake problem, other than usual wear.

Before that, the procedure was to replace both wheel cylinders and all the shoes everytime the damned thing seized, roughly every 3 years on every other car I owned. When I as younger and more foolish, I would take the brakes to Midas and they would change all sorts of stuff, but leave the fluid as dark as it was, unless changing the Master Cylinder. I assume that this was in hopes of zapping me again with their greatly overpriced, not necessarily needed and not all that competent work.

Then a neighbor showed me how to do brakes myself.

The silicone fluid did not change in color in 7 years on the Celica and 6 on the Corona.

On my Mercedes, I used DOT 5.1, being as they don't recommend silicone DOT 5.0.

The question is Being as silicone is so obviously better than hygroscopic fluid that has alcohol in it (which is why it attracts H20, why does MB not use silicone fluid? Is this related to the Automatic Brake Pumper gizmo?

I have a '78 Chevy that I bought new. To date it has 96K miles. I installed new front pads 20K miles ago. The owners manual does not indicate or suggest anywhere that you should ever change the brake fluid. I have never changed the brake fluid and the brakes work perfectly. What do the Chevy folks know that the MB people don't?

Peter;

There is a bit of irony here.
I first heard about changing brake fluid once a year from a woman Mercedes owner who had just had her car serviced at the dealer. I looked at her bill and there it was, "changed brake fluid" on the bill. I thought she had been ripped off, and was a bit pissed! on her behalf of course...
That started a line of inquiry about brake fluid and I learned quite a lot about it.

I agree with you that none of the older american cars or mechanics ever suggested changing brake fluid. Turns out they were wrong. what usually happens is that the master cylinder "goes out"-it's replaced and bled and everything is okay again. It goes out because of the water contamination! Properly maintained and flushed, you actually shouldn't ever have a problem with brakes.

Richard;

You live in a very humid climate and your fluid will get dark rather more quickly than someone in Arizona.

Silicone brake fluid. DOT 5
Standard equipment on Porsches I think.

I have heard of reports from people who have switched to silicone fluid that they experience a softer pedal, and prefer the DOT 5.1. I believe that this is standard equipment on Audi and Jaguar.
I think Jaguar and Lucas were leaders in this fluid and that Jaguar insisted on this fluid in their equipment saying that their seals were incompatible with DOT 3 and 4.

PLEASE DO NOT BUY DOT 3 !! just because it is cheaper...
DOT 4 or DOT 5.1 is compatible and should be used.

After reading the posts here, I am going to change my brake fluid today. I am going to use some DOT 4 fluid, and I am going to use my new vacuum pump/ brake bleeder, I am hoping that everything will work smoothly.

I had problems with my vacuum bleeder today, so I had to do it the old fashioned way, which I still think I didn't get all the air bubbles out because it still feels a little spongy.

Peter, a few decades ago somebody said that there isn't an American solution to every issue. We have the most vehicles, but not all of them. Not bleeding brakes every year is like filling engine oil to the full line on the dipstick.

Here's some tips for vacuum brake bleeding: I use a glass turkey baster to suck out old fluid from reservoir and replace with new before starting. Then tie the brake pedal back (toward the seat). I built a dump jar from a peanut butter jar and three fittings. Two fittings are 3/8in male threaded on one end and barbed on the other. The third is 3/8in female and barbed. Doesn't matter if nylon or brass, buy at a farm or home supply store. Drill two holes in the jar lid, silicone and screw the male fittings into the top of the lid. Screw the female onto one of the males (you might need washers to take up the slack). A small piece of tubing on the inner barb (enough to reach the bottom of the jar), a 1 1/2ft piece between the outer barb and the brake nipple, a 1 1/2ft piece of tubing between the empty barb that is open at the inside of the lid and your hand vacuum pump. Screw the jar on the lid, place it in an old coffee can, loosen the nipple, and pump away (If nothing happens by the fourth or fifth pump then pull the tubing off the nipple and clean out the nipple with a piece of wire or replace it. You don't want the jar to implode and hurt somebody, and this won't happen if you bleed yearly and put a rubber boot over the nipple when done). You only need to make sure you don't empty the car reservoir (start over) and to empty the dump jar before the level reaches the lid (you may get brake fluid in your vacuum pump). The coffee can is dual purpose: helps keep the dump jar upright and provides a place to store the dump jar and tubing. Once you get the hang of it a good job should cost a quart of brake fluid and and hour of time including cleanup. Compare that to the cost of brake parts and time or an accident on the road. Ditto DOT 4 being the minimum spec on the fluid.

I've tried to use my MityVac to bleed my brakes a few times and was never able to get all the air out. I use a system called EZ Bleed that uses pressure instead of vacuum. It has a cap that screws on the top of the resevoir and an air hose that runs to a tire via a small plastic bottle. Just attach a hose to the caliper bleed nipples and bleed away. I don't remember where I bought it but it makes my brake fluid changes easy 15-20 minute jobs. It's a great system and as I recall only cost about $15-20.

I understand very well the lecture on the physics
 

of brake fluids. In reality, most drivers have gome more than 2-yrs without changing the fluid and they're driving fine, safely. This is an item that's not even part of the general motor vehicle inspection in the US. Even with my understanding of the physics, the fluid in my 89 Nissan wasn't changed until a couple of years ago when I had to replace the master cylinder - brake fade was inexistent prior to that and I braked hard, just not continosly hard enough to cause boiling. In normal everyday commute, the brake fluid is perfectly OK after 2 yrs. I don't see any reason to replace it. MB recommends to do it every 2 yrs but it's really your choice. If you race or do a lot of towing or 4-wheeling, or you live in the snow belt, or you do things that require the BAS, ESP to be activated, maybe every 2-yrs.

Old fogie antics...(no offence) people who don't know cars
 

I work in a combination Mechanical/Bodyshop. Alot of our clients have been with us for 30-40 years, and the age is taking it toll on their cars. I've seen all too often an old man comes in and says his brakes don't work. He drives a 2006 Ford contour. the man had put MANY MANY miles and his pads wore out, but before taking it to a shop to have them look at his brakes, he decides that "hey, it's a new car, the pads can't be worn out already, must need brake fluid. " so he goes to the store and buys what he thinks is brake fluid. in reality, it's 10W30 motor oil. DUH.
you can pretty well guess what happens next. calipers, hoses, ABS and master cylinder. REPLACED If I remember correctly, the total bill came to just under $3000 for parts and $500 labour. one of many horror stories.. :)

I change mine every spring because thats what MB calls for and I am very picky. It gives me a chance to really take a look at whats going on under the car, and after 6+ months in winter storage that seems like a good idea.

I had an old english sports car which was seldom driven and stored winters. I was young and foolish (and poor) so never changed the fluid. The brakes worked great until one of the brake lines let go. It was rusted on both the outside AND inside. An extreme example perhaps but I'd rather flush ever couple of years then take the risk.

I thought MB changes the fluid every other year not once a year?

From the CD Manuals for W126
 

The maintenance schedule indicates yearly brake fluid change...in the spring.

Once a year on older cars like the 123 era, every two years on the newer cars.

Len

amazing
 

well this is amazing.
My car is 24 years old and its brake fluid has never been touched or changed.

right now there are poor guys who are reading this thread and believing it and they are breaking off nipples as we speak....and there are other guys who are reading this thread who took your advise and changed the fluid.. now there pulling up to red lights and hitting the pedal and instead of the old trusty brake fluid being down there at the caliper there is a nice fat air bubble.

In the last 40 years I have learned a few things about brakes.
1. Use a large C clamp when you change your brakes....

2. Use a chicken baister and suck some fluid out....making room for your new fluid.

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Apparently, there are still some gaps in your learnin'. A C-clamp is just about useless when dealing with MB type fixed calipers.

If you changed the brake fluid periodically as recommended by the manufacturer it's very unlikely you'll break off a bleed nipple. Try to crack one open after 24 years then that's a whole different story.

change
 

if you change your calipers and master cylinders when they need to be changed you dont have to worry about changing the brake fluid...

The haynes manual will tells you how to use a C clamp on a fixed caliper...
just look in yours and that is how they tell you to do the brake job...

the real trick to mercedes brakes is getting those stupid pins out...

change and ABS
 

not sure if you guys just talk about changing on older cars without ABS, but some cars, like my wife's huyndai (or how u spell crap) has to be wented with a speacial tool of some kind when you change breakfluid...

Does anybody know if the same deal is for my W202 ??? And my MB book says every 2nd year, not every year.. But it also says i should change AC fluid every 4th year...

... and if you change your engine when it needs to be changed you don't have to worry about changing your oil either. :D

BTW, my W123 haynes manual does not say anything about using a c-clamp for the brakes. I very much doubt that you can fit a c-clamp in these calipers.

Blue, you should write your own maintenance manual. May I suggest a title?
"The Idiot's Guide to Saving a Little Now So You Can Spend a Lot Later."

C clamp
 

If you dont like the C clamp then you can stick screw drivers down between the pads and the rotors and pry them back... which is refered to as the cave man technique....

I change my rotors when they start sticking...I can buy them for about 60 bucks so that is why I change them... You can also rebuild them for about 20.

Yes, Craig I actually believe a guy should have a spare engine and spare transmission and change them out periodically....It gives a guy something to do in his garage over the winter. I will be rebuilding my spare transmission this winter... I am actually thinking about rebuilding my engine just for the heck of it...:D

Not to be confused with failing to change your brake fluid for 24 years, which is a totally different technique.

Does the Haynes Manual have a section on "rotor rebuilding" as well? Exactly how does one rebuild a rotor?

never
 

i never change my brake fluid..

I change my calipers, my master cylinder, my booster, my rotors,
and I put fresh fluid in and bleed the system... and since this occors
every few years there is no need to change the fluid...(not all at once)

so I have never changed brake fluid on a car....

MY 24 YEAR OLD CAR HAS BEEN THROUGH PROBABLY 4 SETS OF ROTORS AND 4 MASTER CYLINDERS...