Was told brake flush should be done every 2 years
- Thread starter Carnoobie
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Originally Posted By: Volvohead
The hygroscopic nature of most fluids (except the silicone based ones) certainly helps disperse it some. But if you ever played the conductivity test with the first shot out of a bleeder valve, the values there are much higher than what you'll see at the reservoir in many instances. That's why I don't trust the meter test up top.
All that absorbed moisture does in the upper system is corrode and wear parts.
In the lower end, it causes braking failure and accidents.
I'm coming from a garage and field perspective. But DOT 4 fluids also tend to be more prone to hygroscopic failure than the old DOT 3 types, according to folks more educated on these matters than I. That may also explain why today's high performance braking systems sometimes can't go on for 10 years on the same fluid like a '75 Caprice might have.
These folks have a nice little white paper that does a fair job on the various fluid types and how boiling points become compromised:
http://www.stoptech.com/technical-support/technical-white-papers/brake-fluid
The bottom line is that the worst condition fluid generally is at the bottom of the system, where conditions are the harshest.
V-H
Its nice to know that someone actually has tried to measure a difference between the fluid in parts of the brake system. This is the first evidence I've seen that there may actually be a difference. But without a plasible explanation, this still sounds, to me, more like unchallenged folk-wisdom than anything else.
Maybe even effect-cause thinking as opposed to cause-effect - "The fluid at the wheel boils first, therefore it must be the worst" (ignoring that that is the only place where heat is applied).
Even the paper you cited mentions only the M/C as a potential point of concern re moisture entry.
The hygroscopic nature of most fluids (except the silicone based ones) certainly helps disperse it some. But if you ever played the conductivity test with the first shot out of a bleeder valve, the values there are much higher than what you'll see at the reservoir in many instances. That's why I don't trust the meter test up top.
All that absorbed moisture does in the upper system is corrode and wear parts.
In the lower end, it causes braking failure and accidents.
I'm coming from a garage and field perspective. But DOT 4 fluids also tend to be more prone to hygroscopic failure than the old DOT 3 types, according to folks more educated on these matters than I. That may also explain why today's high performance braking systems sometimes can't go on for 10 years on the same fluid like a '75 Caprice might have.
These folks have a nice little white paper that does a fair job on the various fluid types and how boiling points become compromised:
http://www.stoptech.com/technical-support/technical-white-papers/brake-fluid
The bottom line is that the worst condition fluid generally is at the bottom of the system, where conditions are the harshest.
V-H
Its nice to know that someone actually has tried to measure a difference between the fluid in parts of the brake system. This is the first evidence I've seen that there may actually be a difference. But without a plasible explanation, this still sounds, to me, more like unchallenged folk-wisdom than anything else.
Maybe even effect-cause thinking as opposed to cause-effect - "The fluid at the wheel boils first, therefore it must be the worst" (ignoring that that is the only place where heat is applied).
Even the paper you cited mentions only the M/C as a potential point of concern re moisture entry.
Originally Posted By: TooManyWheels
Maybe even effect-cause thinking as opposed to cause-effect - "The fluid at the wheel boils first, therefore it must be the worst" (ignoring that that is the only place where heat is applied).
Maybe.
Or it could be that the fluid at the calipers gets the hottest, so the fluid there needs to have the highest boiling point. Less margin for compromise down there.
It usually comes out pretty ugly down there if it's been sitting around too long. Undersized rotors, bean-counter swept areas, hard squeaky Chinese pads, it ain't what it used to be. Fortunately, I don't do as much brake work as I used to, so I don't have to deal with it too much anymore. Almost all our cars now specify two years, so I don't think about fluid much anymore either.
To the OP, after two or three years, if you have the spare cash, a fluid flush can never hurt, only help.
I'm a big advocate of spending large on tires and brakes whenever in doubt. It's the stuff that stops the car.
Have a good evening, gents.
Maybe even effect-cause thinking as opposed to cause-effect - "The fluid at the wheel boils first, therefore it must be the worst" (ignoring that that is the only place where heat is applied).
Maybe.
Or it could be that the fluid at the calipers gets the hottest, so the fluid there needs to have the highest boiling point. Less margin for compromise down there.
It usually comes out pretty ugly down there if it's been sitting around too long. Undersized rotors, bean-counter swept areas, hard squeaky Chinese pads, it ain't what it used to be. Fortunately, I don't do as much brake work as I used to, so I don't have to deal with it too much anymore. Almost all our cars now specify two years, so I don't think about fluid much anymore either.
To the OP, after two or three years, if you have the spare cash, a fluid flush can never hurt, only help.
I'm a big advocate of spending large on tires and brakes whenever in doubt. It's the stuff that stops the car.
Have a good evening, gents.
Originally Posted By: Carnoobie
im trying to figure out if i really need this service done right now or can do next year. Its been exactly 2yrs and the shop says do it now but they said they can test it for me. $150 for the service!
Get the Haynes Manual for your car, the tools etc and DIY.
You can probably stretch it to 3 years.
im trying to figure out if i really need this service done right now or can do next year. Its been exactly 2yrs and the shop says do it now but they said they can test it for me. $150 for the service!
Get the Haynes Manual for your car, the tools etc and DIY.
You can probably stretch it to 3 years.
It's somewhat astonishing that, on a forum with membership dedicated to OCD over every minor facet of vehicle maintenance, that a good many choose to be so lax about their brake systems.
Fret ceaselessly over a few PPM in a used oil analysis or VOA that will never manifest itself in real world operation, extract every last drop from the sump by angling the vehicle and adhering to a strict timed interval? Etc. Sure.
The brakes?
Shoot, break out the turkey baster, or just crack the bleeders open and let it run out. Done. That is, whenever I remember to get around to it.
Fret ceaselessly over a few PPM in a used oil analysis or VOA that will never manifest itself in real world operation, extract every last drop from the sump by angling the vehicle and adhering to a strict timed interval? Etc. Sure.
The brakes?
Shoot, break out the turkey baster, or just crack the bleeders open and let it run out. Done. That is, whenever I remember to get around to it.
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JHZR2
Staff member
The calipers and the imperfect seals there are the source of moisture. Diffusion back up through the lines to the reservoir is so long and slow that I doubt it would occur. Moisture can get in through the reservoir though.
Moisture is also heavier than the glycol, so it is more prone to staying next to components which is where the issue lies.
Moisture is also heavier than the glycol, so it is more prone to staying next to components which is where the issue lies.
Originally Posted By: Carmudgeon
It's somewhat astonishing that, on a forum with membership dedicated to OCD over every minor facet of vehicle maintenance, that a good many choose to be so lax about their brake systems.
Fret ceaselessly over a few PPM in a used oil analysis or VOA that will never manifest itself in real world operation, extract every last drop from the sump by angling the vehicle and adhering to a strict timed interval? Etc. Sure.
The brakes?
Shoot, break out the turkey baster, or just crack the bleeders open and let it run out. Done. That is, whenever I remember to get around to it.
It's "break out the turkey baster,or just AND crack the bleeders open and let it run out. Done." This is an easy and effective technique. The differences between this method and using a dedicated brake fluid flushing machine are:
-the machine is faster
-it is possible to botch hookup with a machine and spray brake fluid all over the place
-improper use of the machine can put air into the system
-flushing at other than very low speeds can close valving and stop the flushing process on certain vehicles - older Ford trucks and newer GM trucks come to mind
It's somewhat astonishing that, on a forum with membership dedicated to OCD over every minor facet of vehicle maintenance, that a good many choose to be so lax about their brake systems.
Fret ceaselessly over a few PPM in a used oil analysis or VOA that will never manifest itself in real world operation, extract every last drop from the sump by angling the vehicle and adhering to a strict timed interval? Etc. Sure.
The brakes?
Shoot, break out the turkey baster, or just crack the bleeders open and let it run out. Done. That is, whenever I remember to get around to it.
It's "break out the turkey baster,
-the machine is faster
-it is possible to botch hookup with a machine and spray brake fluid all over the place
-improper use of the machine can put air into the system
-flushing at other than very low speeds can close valving and stop the flushing process on certain vehicles - older Ford trucks and newer GM trucks come to mind
This is the first time I've heard of using a volt meter to test brake fluid condition. When testing Anti-freeze, it is testing for galvanic corrosion and the health of corrosion inhibitors in the coolant. Not sure what or how that applies to brake fluid.
Tomrw going to get my brake flush done and 1 guy is working on it. He said theres a way to bleed the brakes without using the pump the brake pedal method.
How does one person bleed brakes without pumping the brakes? Is the pumping the brakes method really harmful for the MC? I didnt know that, i always thoughrt this is the most common way.
And can this be done without removing tires?
I still do the turkey baster method sucking out from the res every year, except I use a suction gun that I have. Much better. Now that someone else mentioned it, it actually wouldnt be a bad idea to replace the brake res fluid every 6 months instead of every year. Im guessing the MC holds maybe 20% of the entire fluid amount in the car.
How does one person bleed brakes without pumping the brakes? Is the pumping the brakes method really harmful for the MC? I didnt know that, i always thoughrt this is the most common way.
And can this be done without removing tires?
I still do the turkey baster method sucking out from the res every year, except I use a suction gun that I have. Much better. Now that someone else mentioned it, it actually wouldnt be a bad idea to replace the brake res fluid every 6 months instead of every year. Im guessing the MC holds maybe 20% of the entire fluid amount in the car.
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Originally Posted By: Carnoobie
How does one person bleed brakes without pumping the brakes? Is the pumping the brakes method really harmful for the MC? I didnt know that, i always thoughrt this is the most common way.
Not for garages. The pedal-pump method is way too slow, plus it requires two people and it can damage the master cylinder.
There are several non-pedal methods. The best one is called "pressure bleeding". This involves a special adapter-cap being attached to the master cylinder with shop-air fed into it. Then the bleeders are cracked open one-by-one and allowed to run until the fluid is clear. It's quick and efficient. Next best is the vacuum method. This takes longer than the pressure method, but can still be done by one man. The drawback of the vacuum method is that air often gets sucked in through the bleeder threads, and this can make it hard to tell whether or not you've actually got all the air out of the system.
Originally Posted By: Carnoobie
And can this be done without removing tires?
Wheel removal is not necessary, but you do need a hoist for fastest work.
Originally Posted By: Carnoobie
I still do the turkey baster method sucking out from the res every year, except I use a suction gun that I have. Much better. Now that someone else mentioned it, it actually wouldnt be a bad idea to replace the brake res fluid every 6 months instead of every year. Im guessing the MC holds maybe 20% of the entire fluid amount in the car.
Replacing the reservoir fluid does almost nothing. It does absolutely nothing for the bulk of the fluid, which is in the lines and the calipers/wheel cylinders and never transfers to the reservoir. That's why actual bleeding is required, to be done through the four bleed-nipples.
How does one person bleed brakes without pumping the brakes? Is the pumping the brakes method really harmful for the MC? I didnt know that, i always thoughrt this is the most common way.
Not for garages. The pedal-pump method is way too slow, plus it requires two people and it can damage the master cylinder.
There are several non-pedal methods. The best one is called "pressure bleeding". This involves a special adapter-cap being attached to the master cylinder with shop-air fed into it. Then the bleeders are cracked open one-by-one and allowed to run until the fluid is clear. It's quick and efficient. Next best is the vacuum method. This takes longer than the pressure method, but can still be done by one man. The drawback of the vacuum method is that air often gets sucked in through the bleeder threads, and this can make it hard to tell whether or not you've actually got all the air out of the system.
Originally Posted By: Carnoobie
And can this be done without removing tires?
Wheel removal is not necessary, but you do need a hoist for fastest work.
Originally Posted By: Carnoobie
I still do the turkey baster method sucking out from the res every year, except I use a suction gun that I have. Much better. Now that someone else mentioned it, it actually wouldnt be a bad idea to replace the brake res fluid every 6 months instead of every year. Im guessing the MC holds maybe 20% of the entire fluid amount in the car.
Replacing the reservoir fluid does almost nothing. It does absolutely nothing for the bulk of the fluid, which is in the lines and the calipers/wheel cylinders and never transfers to the reservoir. That's why actual bleeding is required, to be done through the four bleed-nipples.
Originally Posted By: Tegger
There are several non-pedal methods. The best one is called "pressure bleeding". This involves a special adapter-cap being attached to the master cylinder with shop-air fed into it. Then the bleeders are cracked open one-by-one and allowed to run until the fluid is clear. It's quick and efficient. Next best is the vacuum method. This takes longer than the pressure method, but can still be done by one man. The drawback of the vacuum method is that air often gets sucked in through the bleeder threads, and this can make it hard to tell whether or not you've actually got all the air out of the system.
Air is sucked through the bleeder threads into the vacuum container along with brake fluid, air can't get back into the brake system.
I used Mityvac 7201 to bleed brake system in 4 cars, none had air in the brake system after work was done. I used Motive Power Bleeder and it didn't work well on the rear for 2 cars.
There are several non-pedal methods. The best one is called "pressure bleeding". This involves a special adapter-cap being attached to the master cylinder with shop-air fed into it. Then the bleeders are cracked open one-by-one and allowed to run until the fluid is clear. It's quick and efficient. Next best is the vacuum method. This takes longer than the pressure method, but can still be done by one man. The drawback of the vacuum method is that air often gets sucked in through the bleeder threads, and this can make it hard to tell whether or not you've actually got all the air out of the system.
Air is sucked through the bleeder threads into the vacuum container along with brake fluid, air can't get back into the brake system.
I used Mityvac 7201 to bleed brake system in 4 cars, none had air in the brake system after work was done. I used Motive Power Bleeder and it didn't work well on the rear for 2 cars.
Originally Posted By: HTSS_TR
Air is sucked through the bleeder threads into the vacuum container along with brake fluid, air can't get back into the brake system.
You are absolutely right.
But my point was that, with the vacuum method, you can't tell the bubbles coming from the threads from bubbles coming from the lines, so you can never be quite sure your system is actually air-free, except by how the pedal feels while driving.
Air is sucked through the bleeder threads into the vacuum container along with brake fluid, air can't get back into the brake system.
You are absolutely right.
But my point was that, with the vacuum method, you can't tell the bubbles coming from the threads from bubbles coming from the lines, so you can never be quite sure your system is actually air-free, except by how the pedal feels while driving.
Originally Posted By: Tegger
But my point was that, with the vacuum method, you can't tell the bubbles coming from the threads from bubbles coming from the lines, so you can never be quite sure your system is actually air-free, except by how the pedal feels while driving.
The brake system should not have any air in it at the beginning of the bleed. If you're connecting the hoses correctly and bump the vacuum bleeder several strokes before loosen the bleeder screw then no air can get into it.
If you have both systems, Motive pressure bleeder and Mityvac fluid extractor( or similar tool), and try both on various cars/trucks made from various companies you will see that Mityvac fluid extractor works better than Motive pressure bleeder on any brake system, for both front and rear.
But my point was that, with the vacuum method, you can't tell the bubbles coming from the threads from bubbles coming from the lines, so you can never be quite sure your system is actually air-free, except by how the pedal feels while driving.
The brake system should not have any air in it at the beginning of the bleed. If you're connecting the hoses correctly and bump the vacuum bleeder several strokes before loosen the bleeder screw then no air can get into it.
If you have both systems, Motive pressure bleeder and Mityvac fluid extractor( or similar tool), and try both on various cars/trucks made from various companies you will see that Mityvac fluid extractor works better than Motive pressure bleeder on any brake system, for both front and rear.
Originally Posted By: Tegger
Originally Posted By: HTSS_TR
Air is sucked through the bleeder threads into the vacuum container along with brake fluid, air can't get back into the brake system.
You are absolutely right.
But my point was that, with the vacuum method, you can't tell the bubbles coming from the threads from bubbles coming from the lines, so you can never be quite sure your system is actually air-free, except by how the pedal feels while driving.
I like to remove the bleeder and use one of the cone shaped adaptors to eliminate that.
Originally Posted By: HTSS_TR
Air is sucked through the bleeder threads into the vacuum container along with brake fluid, air can't get back into the brake system.
You are absolutely right.
But my point was that, with the vacuum method, you can't tell the bubbles coming from the threads from bubbles coming from the lines, so you can never be quite sure your system is actually air-free, except by how the pedal feels while driving.
I like to remove the bleeder and use one of the cone shaped adaptors to eliminate that.
Originally Posted By: Carmudgeon
The brakes?
Shoot, break out the turkey baster, or just crack the bleeders open and let it run out. Done. That is, whenever I remember to get around to it.
You got it...
While the turkey baster isn't optimum there will be some cycling of the fluid from the lines back into the MC, so eventually the new fluid will be distributed throughout the system... Yes it may take a week or two but it most surely will happen...
The brakes?
Shoot, break out the turkey baster, or just crack the bleeders open and let it run out. Done. That is, whenever I remember to get around to it.
You got it...
While the turkey baster isn't optimum there will be some cycling of the fluid from the lines back into the MC, so eventually the new fluid will be distributed throughout the system... Yes it may take a week or two but it most surely will happen...
Originally Posted By: Tegger
Originally Posted By: Carnoobie
How does one person bleed brakes without pumping the brakes? Is the pumping the brakes method really harmful for the MC? I didnt know that, i always thoughrt this is the most common way.
Not for garages. The pedal-pump method is way too slow, plus it requires two people and it can damage the master cylinder.
There are several non-pedal methods. The best one is called "pressure bleeding". This involves a special adapter-cap being attached to the master cylinder with shop-air fed into it. Then the bleeders are cracked open one-by-one and allowed to run until the fluid is clear. It's quick and efficient. Next best is the vacuum method. This takes longer than the pressure method, but can still be done by one man. The drawback of the vacuum method is that air often gets sucked in through the bleeder threads, and this can make it hard to tell whether or not you've actually got all the air out of the system.
Originally Posted By: Carnoobie
And can this be done without removing tires?
Wheel removal is not necessary, but you do need a hoist for fastest work.
Originally Posted By: Carnoobie
I still do the turkey baster method sucking out from the res every year, except I use a suction gun that I have. Much better. Now that someone else mentioned it, it actually wouldnt be a bad idea to replace the brake res fluid every 6 months instead of every year. Im guessing the MC holds maybe 20% of the entire fluid amount in the car.
Replacing the reservoir fluid does almost nothing. It does absolutely nothing for the bulk of the fluid, which is in the lines and the calipers/wheel cylinders and never transfers to the reservoir. That's why actual bleeding is required, to be done through the four bleed-nipples.
Well I had the brakes flushed yesterday and the guy took the wheels off and we did the pedal pump method. It took an hour.
Bad?
Originally Posted By: Carnoobie
How does one person bleed brakes without pumping the brakes? Is the pumping the brakes method really harmful for the MC? I didnt know that, i always thoughrt this is the most common way.
Not for garages. The pedal-pump method is way too slow, plus it requires two people and it can damage the master cylinder.
There are several non-pedal methods. The best one is called "pressure bleeding". This involves a special adapter-cap being attached to the master cylinder with shop-air fed into it. Then the bleeders are cracked open one-by-one and allowed to run until the fluid is clear. It's quick and efficient. Next best is the vacuum method. This takes longer than the pressure method, but can still be done by one man. The drawback of the vacuum method is that air often gets sucked in through the bleeder threads, and this can make it hard to tell whether or not you've actually got all the air out of the system.
Originally Posted By: Carnoobie
And can this be done without removing tires?
Wheel removal is not necessary, but you do need a hoist for fastest work.
Originally Posted By: Carnoobie
I still do the turkey baster method sucking out from the res every year, except I use a suction gun that I have. Much better. Now that someone else mentioned it, it actually wouldnt be a bad idea to replace the brake res fluid every 6 months instead of every year. Im guessing the MC holds maybe 20% of the entire fluid amount in the car.
Replacing the reservoir fluid does almost nothing. It does absolutely nothing for the bulk of the fluid, which is in the lines and the calipers/wheel cylinders and never transfers to the reservoir. That's why actual bleeding is required, to be done through the four bleed-nipples.
Well I had the brakes flushed yesterday and the guy took the wheels off and we did the pedal pump method. It took an hour.
Bad?
Originally Posted By: Carnoobie
Well I had the brakes flushed yesterday and the guy took the wheels off and we did the pedal pump method. It took an hour.
Bad?
Did he make sure to place a block of wood underneath the brake pedal so that he didn't damage the master cylinder seal? If you pump the pedal further than normal their is a sharp ridge that develops which can dig into the seal damaging it, and causing the MC to fail.
Well I had the brakes flushed yesterday and the guy took the wheels off and we did the pedal pump method. It took an hour.
Bad?
Did he make sure to place a block of wood underneath the brake pedal so that he didn't damage the master cylinder seal? If you pump the pedal further than normal their is a sharp ridge that develops which can dig into the seal damaging it, and causing the MC to fail.
Originally Posted By: Carnoobie
Well I had the brakes flushed yesterday and the guy took the wheels off and we did the pedal pump method. It took an hour. Bad?
Does the brake pedal feel the same as it did before? Then no harm done.
If you're sitting at a light and the pedal s-l-o-w-l-y goes to the floor, then the master cylinder seals are bad, and were possibly damaged during the bleed procedure.
Well I had the brakes flushed yesterday and the guy took the wheels off and we did the pedal pump method. It took an hour. Bad?
Does the brake pedal feel the same as it did before? Then no harm done.
If you're sitting at a light and the pedal s-l-o-w-l-y goes to the floor, then the master cylinder seals are bad, and were possibly damaged during the bleed procedure.
Originally Posted By: antiqueshell
Originally Posted By: Carnoobie
Well I had the brakes flushed yesterday and the guy took the wheels off and we did the pedal pump method. It took an hour.
Bad?
Did he make sure to place a block of wood underneath the brake pedal so that he didn't damage the master cylinder seal? If you pump the pedal further than normal their is a sharp ridge that develops which can dig into the seal damaging it, and causing the MC to fail.
No he didnt. He got me to pump the brake as far as itll go really hard each time. I asked him why we push to the hardest furthest back and he said something about it getting all the air out of the line. Im guessing tthis is really bad? Now how can i check to see if my MC seal is not damaged?
Originally Posted By: Carnoobie
Well I had the brakes flushed yesterday and the guy took the wheels off and we did the pedal pump method. It took an hour.
Bad?
Did he make sure to place a block of wood underneath the brake pedal so that he didn't damage the master cylinder seal? If you pump the pedal further than normal their is a sharp ridge that develops which can dig into the seal damaging it, and causing the MC to fail.
No he didnt. He got me to pump the brake as far as itll go really hard each time. I asked him why we push to the hardest furthest back and he said something about it getting all the air out of the line. Im guessing tthis is really bad? Now how can i check to see if my MC seal is not damaged?
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Originally Posted By: antiqueshell
their is a sharp ridge that develops which can dig into the seal damaging it, and causing the MC to fail.
Not a sharp ridge, just some corrosion or deposits on the surface of the bore. If this corrosion or crud is heavy enough, it can tear the delicate lip of the rubber seal, causing it to eventually leak.
their is a sharp ridge that develops which can dig into the seal damaging it, and causing the MC to fail.
Not a sharp ridge, just some corrosion or deposits on the surface of the bore. If this corrosion or crud is heavy enough, it can tear the delicate lip of the rubber seal, causing it to eventually leak.
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