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Brake fluid flush???
11-03-2011, 02:52 PM
#21
First it decreases performance as water has a higher compressibility rate vs. brake fluid. Temperature will affect rate of change which gives less predicable and repeatable results. This is why the wet boiling point comes into factor too. The delta change is not linear either.
11-03-2011, 03:07 PM
#22
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It proportional with temperature and pressure which is different that of the brake fluid so I can't give you an exact set number. You could take one instance in time and measure the differences and then extrapolate values based on estimated conditions but for all intensive purposes on this forum, just take it for what it is:-). This is one reason why brakes can feel "mushy" when the brake fluid is highly diluted, it will be worse at some times based on said conditions. You'll have to look at a vapor dome and other data for comparison if you want to get more technical about it.
11-03-2011, 03:44 PM
#23
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SJM- You got it right on. As I was reading through, I was wondering if anyone was going to mention that the water absorbtion rusts out the brakes lines internally.
I work for a dealer that sells BMW, Mercedes-Benz, Porsche, Saab, Volkswagen and Mazda. All the German brands have a set replacement time for brake flushes, usually during the maintenances. (20k, 30k...) I work the Mazda line and they do not have a set replacement time. Only to check it every 5K and replace as needed. We used to combine it with our maintenances as well, every 30K. My manager recently removed them from the maintenances saying that "Mazda doesnt recommend it at certain intervals, so we're not doing it". So now its a lot harder to sell these flushes to customers at seperate times or now saying when they do come in for the maintenance that its also recommended to do the flush and its gonna cost this much more...... We charge $120 I believe, (2 pints of fluid+labor). Alot of people dont believe in doing this, mostly because they have never known it was done or just think "hey, my brakes work just fine when I step on the pedal, what are they trying to sell me now that i dont need" The whole "stealership" thing...... We use a vacuum based tool to pull the fluid through to each caliper. When I empty it, not only do you get this dark fluid from the water absorbtion, but there's usually a sort of sediment at the bottom of dirt/metal particles. Just think of what that stuff is doing to your piston seals as they work back and forth everytime! And how well does the water provide lubrication to seals and pistons versus fresh brake fluid? Plus think that your brake fluid goes through how many heat cycles, just like trans fluid and engine oil, causing a break down of its properties over time. Why would you not change your brake fluid just the same as you do your engine oil, trans fluid, differential oil.....etc. The only time I do not usually recommend this is when its a high mileage vehicle that has never had it done before. I know that the bleeders have never been opened before and I dont want to risk breaking one off.
I work for a dealer that sells BMW, Mercedes-Benz, Porsche, Saab, Volkswagen and Mazda. All the German brands have a set replacement time for brake flushes, usually during the maintenances. (20k, 30k...) I work the Mazda line and they do not have a set replacement time. Only to check it every 5K and replace as needed. We used to combine it with our maintenances as well, every 30K. My manager recently removed them from the maintenances saying that "Mazda doesnt recommend it at certain intervals, so we're not doing it". So now its a lot harder to sell these flushes to customers at seperate times or now saying when they do come in for the maintenance that its also recommended to do the flush and its gonna cost this much more...... We charge $120 I believe, (2 pints of fluid+labor). Alot of people dont believe in doing this, mostly because they have never known it was done or just think "hey, my brakes work just fine when I step on the pedal, what are they trying to sell me now that i dont need" The whole "stealership" thing...... We use a vacuum based tool to pull the fluid through to each caliper. When I empty it, not only do you get this dark fluid from the water absorbtion, but there's usually a sort of sediment at the bottom of dirt/metal particles. Just think of what that stuff is doing to your piston seals as they work back and forth everytime! And how well does the water provide lubrication to seals and pistons versus fresh brake fluid? Plus think that your brake fluid goes through how many heat cycles, just like trans fluid and engine oil, causing a break down of its properties over time. Why would you not change your brake fluid just the same as you do your engine oil, trans fluid, differential oil.....etc. The only time I do not usually recommend this is when its a high mileage vehicle that has never had it done before. I know that the bleeders have never been opened before and I dont want to risk breaking one off.
11-03-2011, 05:34 PM
#24
It proportional with temperature and pressure which is different that of the brake fluid so I can't give you an exact set number. You could take one instance in time and measure the differences and then extrapolate values based on estimated conditions but for all intensive purposes on this forum, just take it for what it is:-). This is one reason why brakes can feel "mushy" when the brake fluid is highly diluted, it will be worse at some times based on said conditions. You'll have to look at a vapor dome and other data for comparison if you want to get more technical about it.
Like they say ester base (like Castrol SRF, which does also have glycol) is more compressible than the glycol but I doubt many notice it too much in pedal feel. They also say the sillicone DOT5 is something like 2-3 times more compressible and is noticeable, although I have never driven a car with silicone fluid.
11-03-2011, 08:01 PM
#25
I honestly doubt a regular Joe in a street car with OEm type barkes could feel the compressibility difference between water, glycol and ester based fluids.
But only one of those fluids transitions to a gas at 212* and I would hope that ANY Joe could feel the difference between water, glycol, ester and steam.
And at 80* ambient temps, it doesn't take very much braking to reach 212*.
The bad thing is that when fluid boiling occurs, its typically when you really need your brakes ... and you don't have them.
But only one of those fluids transitions to a gas at 212* and I would hope that ANY Joe could feel the difference between water, glycol, ester and steam.
And at 80* ambient temps, it doesn't take very much braking to reach 212*.
The bad thing is that when fluid boiling occurs, its typically when you really need your brakes ... and you don't have them.
11-03-2011, 08:52 PM
#26
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So I went to Firestone today and after getting my tires rotated the mechanic does his usual list of recommended maintenance. He tells me my brake fluid needs flushed, that it's registering this color on his stick that he uses to check it, and that means it is "dangerously" dirty. I haven't had a look at the fluid myself yet but I was wondering what everyone's thoughts on this were.
1. Are brake fluid flushes required? Necessary? Recommended? They wanted to charge me $63 for one.
2. Can I do a brake flush myself? Or just drain the fluid and refill it with new stuff?
Thanks in advance.
1. Are brake fluid flushes required? Necessary? Recommended? They wanted to charge me $63 for one.
2. Can I do a brake flush myself? Or just drain the fluid and refill it with new stuff?
Thanks in advance.
11-04-2011, 10:11 PM
#27
Those people are idiots, they're killing their bearings. Brake fluid sits still basically and moves back and forth..........LITTLE different then engine oil bud.....
What I was TRYING to say was that the mechanic is a cheeseball to say "dangerously" dirty. No such thing. Brakes don't have dirty, old fluid and then one day 100% stop working, making it dangerous.
My brake fluid, as of a month ago, was 13 1/2 years old. I never once even had to top off the fluid. It was clean and just fine. So if his was "dangerously" dirty....then I should have crashed like 8-9 years ago.
Typical mechanic scare tactics to get work.............
My brake system now has steel lines and high performance fluid.....I won't change the fluid for years, no way......
.
What I was TRYING to say was that the mechanic is a cheeseball to say "dangerously" dirty. No such thing. Brakes don't have dirty, old fluid and then one day 100% stop working, making it dangerous.
My brake fluid, as of a month ago, was 13 1/2 years old. I never once even had to top off the fluid. It was clean and just fine. So if his was "dangerously" dirty....then I should have crashed like 8-9 years ago.
Typical mechanic scare tactics to get work.............
My brake system now has steel lines and high performance fluid.....I won't change the fluid for years, no way......
.
11-04-2011, 11:43 PM
#28
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Those people are idiots, they're killing their bearings. Brake fluid sits still basically and moves back and forth..........LITTLE different then engine oil bud.....
What I was TRYING to say was that the mechanic is a cheeseball to say "dangerously" dirty. No such thing. Brakes don't have dirty, old fluid and then one day 100% stop working, making it dangerous.
My brake fluid, as of a month ago, was 13 1/2 years old. I never once even had to top off the fluid. It was clean and just fine. So if his was "dangerously" dirty....then I should have crashed like 8-9 years ago.
Typical mechanic scare tactics to get work.............
My brake system now has steel lines and high performance fluid.....I won't change the fluid for years, no way......
.
What I was TRYING to say was that the mechanic is a cheeseball to say "dangerously" dirty. No such thing. Brakes don't have dirty, old fluid and then one day 100% stop working, making it dangerous.
My brake fluid, as of a month ago, was 13 1/2 years old. I never once even had to top off the fluid. It was clean and just fine. So if his was "dangerously" dirty....then I should have crashed like 8-9 years ago.
Typical mechanic scare tactics to get work.............
My brake system now has steel lines and high performance fluid.....I won't change the fluid for years, no way......
.
Is your brake fluid still crystal clear as it was 13.58 years ago? Completely devoid of color or haze?
11-05-2011, 04:06 AM
#30
honestly you may need a shop to do it. with the abs modules, it's possible to get air trapped in there resulting in less than optimal performance. could you get a decent pedal doing it at home? eh probably. but letting a shop with the equipment to purge the abs system is the best route.
But, then again, bleeding with a buddy using the 'top off...pump...pump...pump...HOLD DOWN...release' and repeat method won't introduce air into the system either. Unless, you let the master cylinder do dry.
11-05-2011, 07:26 AM
#31
I was just using your logic, that's all. Faulty logic ... but logic, none the less.
Again, using your logic and thought process, a fluid that's hygroscopic and is 100% saturated with water (brake fluid is hygroscopic and begins absorbing humidity immediately) and then sits in metal lines for 13.5 years will cause no degredation to metal parts.
Is that really how you think?
Do you ever change your brake pads? Metal backing plates will actually stop the car, so what's the point, right?
Interesting ...
Oh and in a solid, presurized system like a braking system, the fluid doesn't "move back and forth". It simply compresses, creating hydraulilc pressure. There is movement ... miniscual movement ... more at the master cyclinder and almost nothing at the caliper. But it doesn't flow through the lines like in a power steering system.
11-05-2011, 08:10 AM
#32
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Well I have been following this thread for a day or two now. I had been waiting for the weekend to come to change my brake fluid and holy $hit was it nasty. A buddy helped my change it out and it looks like soda. We used the motive pressure bleeder and flushed the whole system out and neither of us could believe how nasty the fluid was.
11-05-2011, 08:18 AM
#33
LITTLE different than engine oil bud ... irony is a bitch, ain't it?
I was just using your logic, that's all. Faulty logic ... but logic, none the less.
Again, using your logic and thought process, a fluid that's hygroscopic and is 100% saturated with water (brake fluid is hygroscopic and begins absorbing humidity immediately) and then sits in metal lines for 13.5 years will cause no degredation to metal parts.
Is that really how you think?
Do you ever change your brake pads? Metal backing plates will actually stop the car, so what's the point, right?
Interesting ...
Oh and in a solid, presurized system like a braking system, the fluid doesn't "move back and forth". It simply compresses, creating hydraulilc pressure. There is movement ... miniscual movement ... more at the master cyclinder and almost nothing at the caliper. But it doesn't flow through the lines like in a power steering system.
I was just using your logic, that's all. Faulty logic ... but logic, none the less.
Again, using your logic and thought process, a fluid that's hygroscopic and is 100% saturated with water (brake fluid is hygroscopic and begins absorbing humidity immediately) and then sits in metal lines for 13.5 years will cause no degredation to metal parts.
Is that really how you think?
Do you ever change your brake pads? Metal backing plates will actually stop the car, so what's the point, right?
Interesting ...
Oh and in a solid, presurized system like a braking system, the fluid doesn't "move back and forth". It simply compresses, creating hydraulilc pressure. There is movement ... miniscual movement ... more at the master cyclinder and almost nothing at the caliper. But it doesn't flow through the lines like in a power steering system.
08-19-2013, 08:54 AM
#37
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That guy is full of **** man.....no such thing as "dangerously" dirty......I just changed my fluid after 13 1/2 years. It just gets moisture in it, making the brakes mushy over years and years......its not like one second you have brakes and the next you die...... 
They will always keep working as long as you don't spring a big leak and have no pressure.
I did steal braided lines last month so I thought I'd flush the entire system while we were at it.
It takes two guys 15 minutes to bleed all the old fluid out and the new fluid in. EASY...... They even have a little gizmo now so you can do it all by yourself......
Simply bleed the brakes one at a time.....take a turkey baster and suck all the brake fluid you can out of the master cylinder. Then top it off with new fluid. Starting with the REAR RIGHT..Bleed it till new, clean fluid comes out. Then top off the fluid again. Then go to the REAR LEFT till new fluid comes out. Top of the fluid. Then go to the FRONT RIGHT till new fluid comes out. Top of the fluid. Then go to the FRONT LEFT and bleed it till new fluid comes out. Now the entire system has new fluid, except a tiny dribble in the ABS box....meaningless.
Each time you bleed a caliper, the fluid in the master cylinder doesn't really drop that much......BUT make sure you DO NOT let it run dry.
We had to go around and bleed them TWO times......just because I wanted to make sure all the old was out and all the air.
.
They will always keep working as long as you don't spring a big leak and have no pressure.I did steal braided lines last month so I thought I'd flush the entire system while we were at it.
It takes two guys 15 minutes to bleed all the old fluid out and the new fluid in. EASY...... They even have a little gizmo now so you can do it all by yourself......
Simply bleed the brakes one at a time.....take a turkey baster and suck all the brake fluid you can out of the master cylinder. Then top it off with new fluid. Starting with the REAR RIGHT..Bleed it till new, clean fluid comes out. Then top off the fluid again. Then go to the REAR LEFT till new fluid comes out. Top of the fluid. Then go to the FRONT RIGHT till new fluid comes out. Top of the fluid. Then go to the FRONT LEFT and bleed it till new fluid comes out. Now the entire system has new fluid, except a tiny dribble in the ABS box....meaningless.
Each time you bleed a caliper, the fluid in the master cylinder doesn't really drop that much......BUT make sure you DO NOT let it run dry.
We had to go around and bleed them TWO times......just because I wanted to make sure all the old was out and all the air.
.
08-19-2013, 10:08 AM
#39
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08-20-2013, 07:42 AM
#40
I change my brake fluid when I open the cap to check it (every time I change my oil) and it has a hint of a brown tint to it. I usually don't bleed the fluid out though. I use a turkey baster and suck all the fluid out of the reservoir and then top it back off. Yeah i know its a half *** way to do it but it better than doing nothing at all. So far I've done this ~ 5 times since the car was new.