Time to do Brake system flush
05-08-2003, 02:07 PM
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Time to do Brake system flush
What is a reasonable time for the completion of a brake system flush? I was going to purchase a brake bleeder and do it myself but I ran out of time. Thanks
05-08-2003, 02:22 PM
#2
Including jacking up the car and removing the wheels, it takes me 1 hour. I use the Motive Pressure Bleeder. Of course, I must take an occasional break for a sip of "iced tea".
Bruce
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05-08-2003, 05:40 PM
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</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"><strong>otherwise about every ten years.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">What's that about?
05-08-2003, 05:57 PM
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Hi
If you have a pressure bleeder (I use a motive) you can do it in half an hour. You don't even have to take the wheels off, just raise it up onto axle stands.
Cheers
If you have a pressure bleeder (I use a motive) you can do it in half an hour. You don't even have to take the wheels off, just raise it up onto axle stands.
Cheers
05-08-2003, 10:16 PM
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Bronco Billy is correct. Flush every two years under normal use. if you autocross or do DE's, as required. All kinds of sediment and crud can get into the system and cause the parts to pit and corrode. When that happens, the Master Cylinder and other parts may need/require replacement.
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05-09-2003, 02:49 AM
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Sediment and crud....
Ever think about how high the brake fluid pressures are under severe braking and yet NONE of the fluid escapes. And think of the rat-a-tat hydraulic hammer (water goat) as the ABS, PSM or Trac pulses those high pressures on and off rapidly.
Yet sediment and crud seems to get in and contaminate the fluid.
NOT!
As long as my brakes are operating satisfactorily NO ONE touches them!
Ever think about how high the brake fluid pressures are under severe braking and yet NONE of the fluid escapes. And think of the rat-a-tat hydraulic hammer (water goat) as the ABS, PSM or Trac pulses those high pressures on and off rapidly.
Yet sediment and crud seems to get in and contaminate the fluid.
NOT!
As long as my brakes are operating satisfactorily NO ONE touches them!
05-09-2003, 03:28 AM
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Brake fluid is hygroscopic, which means that absorbs moisture over time, and that is why the fluid should be changed every 2 years (that is for Dot 3 & 4). The real problem comes from 2 sides:
1.- As moisture gets into the system, the fluid is more prone to boiling under heavy braking (suddenly, no brakes!)
2.- Moisture corrodes contacts and hydraulic parts in the system (one of the clearest symptoms in our cars, is that the brake light connectors in the brake fluid reservoir stop working correctly, due to corrosion).
Apart from these facts... everyone is free to do as they wish on their cars...
1.- As moisture gets into the system, the fluid is more prone to boiling under heavy braking (suddenly, no brakes!)
2.- Moisture corrodes contacts and hydraulic parts in the system (one of the clearest symptoms in our cars, is that the brake light connectors in the brake fluid reservoir stop working correctly, due to corrosion).
Apart from these facts... everyone is free to do as they wish on their cars...
05-09-2003, 07:04 AM
#10
Burning Brakes
All cars should have their brake fluid changed every 2/3 years, according to the manufacturers - for the reasons given by carlitox. The exception is silicon dot 5 which is for life as it is not hygroscopic, it is also non-corrosive unlike standard brake fluids (ie. it can take your paint off!). This is great fluid for cars that are not used hard. I have had it in my '76 911 for 10 years and only replaced it recently when I did a brake overhaul ie. replaced the flexibles, removed and checked calipers. It was as good as new on removal, no crap or discoloration. But it is obviously up to the individual.
I find a vacuum system is better, drawing the fluid down through the system rather than pressurising. The problem with using a pressure system on some 911's is that they have a breather tube out of the reservoir and this has to be squeezed off or you finish up with fluid all over the floor.
PJC
I find a vacuum system is better, drawing the fluid down through the system rather than pressurising. The problem with using a pressure system on some 911's is that they have a breather tube out of the reservoir and this has to be squeezed off or you finish up with fluid all over the floor.
PJC
05-09-2003, 10:35 AM
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If you switch to DOT 5 be sure to remove all previous brake fluid. I understand that it is also sometimes difficult to bleed the brakes properly as the air wants to hand around in the lines. Anyone have experience with this?
Tim
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05-09-2003, 01:03 PM
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yes, brake fluid is hygroscopic, VERY, same as 100 proof liquor.
Now, even with the fluid "sucking", can you tell me how moisture gets into your brake system?
And in any case there cannot be a suddenness to brake loss due to moisture absortion, my guess is that it would take ten years to lose 10% braking capability.
If you have someone to change/flush your brake fluid that you trust with your life and the life of your loved ones then go ahead and do it every two years.
But I would bet you that more brake failures, or reductions in braking capability, result from these schedules than would by just ignoring them.
Now, even with the fluid "sucking", can you tell me how moisture gets into your brake system?
And in any case there cannot be a suddenness to brake loss due to moisture absortion, my guess is that it would take ten years to lose 10% braking capability.
If you have someone to change/flush your brake fluid that you trust with your life and the life of your loved ones then go ahead and do it every two years.
But I would bet you that more brake failures, or reductions in braking capability, result from these schedules than would by just ignoring them.
05-10-2003, 12:00 PM
#13
Burning Brakes
Easy man - air has contact with the fluid through the breather tube, air contains moisture (in most countries - maybe not Seattle?. Brake fluid sucks in water like its dehydrated. Apart from a gradual loss of braking efficiency the water starts to rot out the brake system from the inside - hence the need to refurbish calipers, or in some cases completely replace them. Look at the colour of the brake fluid if its been in place for several years - it comes out looking "rusty" - guess why?
Guess you don't change your tires either Willard?
pjc
Guess you don't change your tires either Willard?
pjc
05-10-2003, 12:23 PM
#14
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by willard:
<strong>. . .
Now, even with the fluid "sucking", can you tell me how moisture gets into your brake system?
And in any case there cannot be a suddenness to brake loss due to moisture absortion, my guess is that it would take ten years to lose 10% braking capability.
If you have someone to change/flush your brake fluid that you trust with your life and the life of your loved ones then go ahead and do it every two years.
But I would bet you that more brake failures, or reductions in braking capability, result from these schedules than would by just ignoring them.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">The moisture enters the system primarily through the vent hole in the master cylinder reservoir and when you remove the lid to check the fluid. Rubber is porous and H2O is a rather small molecule so some water makes it past the rubber membrane seal in the reservoir. If your brake system is never opened (such as when serviced once every ten years when the master cylinder becomes unusable because of neglected fluid) a major source of moisture will be from moisture contamination of the brake fluid that impregnates the porosity of the metal that makes up the master cylinder bores. Every time you step on the brake a large portion of the master cylinder bore is exposed to air. Metal is porous and the brake fluid is in those pores acting as a lubricant. When you take your foot off the brake the now contaminated residual fluid is back on the other side of the piston and osmosis will distribute it though the fluid. It will also pull some moisture past the seals in the calipers but the wheel cylinders on drum brake cars were much more prone to this as the piston travel was much larger.
Now for the damage... Any components made of iron will have an obvious problem with rust and then component wear from the abrasive action of rust particles in the fluid. Corrosion on aluminum parts might not seem like a concern, as most people don't think aluminum will oxidize. Aluminum Oxide... Hmmm... Sandpaper! Aluminum will oxidize very nicely but only till the layer of oxidation seals the aluminum from the further contact with moisture/air. On your intake manifold or engine parts this is fine. On the surface of an extremely precise hydraulic cylinder, this is destructive.
Gunk in the brake fluid? I've never seen it happen. I have seen lots of cases where there is a dark colored contamination that is actually particles of oxidization and metal mixed with the brake fluid. This is generally a sign that the master cylinder or caliper should be chucked. Hanging on my Wall Of Shame is a front brake pad that had no external symptoms of any brake problems. It didn't loose fluid, squeal, or pull to the side. One corner of it is worn till the metal backing touched the rotor. The opposite corner has an area that is about 1/4" wide that has never touched the rotor. The whole thing is worn at an extreme angle. Why? The caliper bore is pitted because the previous owner never changed the fluid.
There might be a reason that EVERY car manufacturer recommends that the fluid be replaced every 2 years. Probably because it needs it and it is a safety issue that they don't want to be sued over.
Waynw
<strong>. . .
Now, even with the fluid "sucking", can you tell me how moisture gets into your brake system?
And in any case there cannot be a suddenness to brake loss due to moisture absortion, my guess is that it would take ten years to lose 10% braking capability.
If you have someone to change/flush your brake fluid that you trust with your life and the life of your loved ones then go ahead and do it every two years.
But I would bet you that more brake failures, or reductions in braking capability, result from these schedules than would by just ignoring them.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">The moisture enters the system primarily through the vent hole in the master cylinder reservoir and when you remove the lid to check the fluid. Rubber is porous and H2O is a rather small molecule so some water makes it past the rubber membrane seal in the reservoir. If your brake system is never opened (such as when serviced once every ten years when the master cylinder becomes unusable because of neglected fluid) a major source of moisture will be from moisture contamination of the brake fluid that impregnates the porosity of the metal that makes up the master cylinder bores. Every time you step on the brake a large portion of the master cylinder bore is exposed to air. Metal is porous and the brake fluid is in those pores acting as a lubricant. When you take your foot off the brake the now contaminated residual fluid is back on the other side of the piston and osmosis will distribute it though the fluid. It will also pull some moisture past the seals in the calipers but the wheel cylinders on drum brake cars were much more prone to this as the piston travel was much larger.
Now for the damage... Any components made of iron will have an obvious problem with rust and then component wear from the abrasive action of rust particles in the fluid. Corrosion on aluminum parts might not seem like a concern, as most people don't think aluminum will oxidize. Aluminum Oxide... Hmmm... Sandpaper! Aluminum will oxidize very nicely but only till the layer of oxidation seals the aluminum from the further contact with moisture/air. On your intake manifold or engine parts this is fine. On the surface of an extremely precise hydraulic cylinder, this is destructive.
Gunk in the brake fluid? I've never seen it happen. I have seen lots of cases where there is a dark colored contamination that is actually particles of oxidization and metal mixed with the brake fluid. This is generally a sign that the master cylinder or caliper should be chucked. Hanging on my Wall Of Shame is a front brake pad that had no external symptoms of any brake problems. It didn't loose fluid, squeal, or pull to the side. One corner of it is worn till the metal backing touched the rotor. The opposite corner has an area that is about 1/4" wide that has never touched the rotor. The whole thing is worn at an extreme angle. Why? The caliper bore is pitted because the previous owner never changed the fluid.
There might be a reason that EVERY car manufacturer recommends that the fluid be replaced every 2 years. Probably because it needs it and it is a safety issue that they don't want to be sued over.
Waynw
05-11-2003, 01:59 AM
#15
Willard, many cars seem to work fine without changing the fluid for 10 years, but then again they are probably not driven like Porsches. And then again, I can't tell you how many times I have seen people replacing brake parts that are in horrible shape that may be 10 years old or less.
Flush your brake fluid, you'll notice that the stuff that comes out doesn't look anything like the stuff that went in. If it's old enough you will not only see stuff floating in it, but also sediment in the bottom of the container that the old fluid goes into. Would you want to pour sand into your master cylinder? No, of course not, then why would you leave crap in there for 10 years. Do your own brakes, you should trust yourself. If you rebuild the calipers assuming you don't have aluminum pistons you'll see rust on the old pistons at some point, that's from water in the system.
As for the sudden loss of braking efficiency due to water in the system, it can happen. "As moisture gets into the system, the fluid is more prone to boiling under heavy braking (suddenly, no brakes!)"
The important thing to note here is the "heavy braking" part. Imagine this, you have moisture in your system (it just happens) and you go out for a spirited drive on your favorite backroads or you go to your first high speed driver's education event. You have been really pushing the car for 15-20 minutes you come to the end of a straight and get ready to stand on the brakes when the pedal goes to the floor. Why, you have water in the system, the system gets up to a few hundred degrees because you have been working the brakes really hard, finally the water boils in the fluid, air is in the system, and the pedal goes to the floor.
Sorry, in this instance you are just not correct.
Who are we to say we are smarter than then very well educated and paid engineers at Porsche.
Flush your brake fluid, you'll notice that the stuff that comes out doesn't look anything like the stuff that went in. If it's old enough you will not only see stuff floating in it, but also sediment in the bottom of the container that the old fluid goes into. Would you want to pour sand into your master cylinder? No, of course not, then why would you leave crap in there for 10 years. Do your own brakes, you should trust yourself. If you rebuild the calipers assuming you don't have aluminum pistons you'll see rust on the old pistons at some point, that's from water in the system.
As for the sudden loss of braking efficiency due to water in the system, it can happen. "As moisture gets into the system, the fluid is more prone to boiling under heavy braking (suddenly, no brakes!)"
The important thing to note here is the "heavy braking" part. Imagine this, you have moisture in your system (it just happens) and you go out for a spirited drive on your favorite backroads or you go to your first high speed driver's education event. You have been really pushing the car for 15-20 minutes you come to the end of a straight and get ready to stand on the brakes when the pedal goes to the floor. Why, you have water in the system, the system gets up to a few hundred degrees because you have been working the brakes really hard, finally the water boils in the fluid, air is in the system, and the pedal goes to the floor.
Sorry, in this instance you are just not correct.
Who are we to say we are smarter than then very well educated and paid engineers at Porsche.