Flushing Brakes Without First Drain/ Refill Master
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Originally Posted By: 2civics
My back breaks are drums. I assume there are no pistons to push back?
There should be, it's just the shoes will only push back as far as the adjuster lets them. You should be able to push the pistons back into the bores with your fingers though.
My back breaks are drums. I assume there are no pistons to push back?
There should be, it's just the shoes will only push back as far as the adjuster lets them. You should be able to push the pistons back into the bores with your fingers though.
Originally Posted By: Brad_C
Originally Posted By: 2civics
My back breaks are drums. I assume there are no pistons to push back?
There should be, it's just the shoes will only push back as far as the adjuster lets them. You should be able to push the pistons back into the bores with your fingers though.
Alright. Thank you.
Originally Posted By: 2civics
My back breaks are drums. I assume there are no pistons to push back?
There should be, it's just the shoes will only push back as far as the adjuster lets them. You should be able to push the pistons back into the bores with your fingers though.
Alright. Thank you.
So you just siphon out and refill the brake reservoir with new fluid and then open and close the bleeders one at a time and let them slowly drain out 4-6oz's fluid? Then keep filling the reservoir.
Do not press on the brake pedal, right? I think I used to do this on my older cars and it took about 10-15 minutes per corner to get the right amount of fluid out. I was not sure if you could still do this procedure on newer cars... Thanks.
Do not press on the brake pedal, right? I think I used to do this on my older cars and it took about 10-15 minutes per corner to get the right amount of fluid out. I was not sure if you could still do this procedure on newer cars... Thanks.
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Brake fluid is hygroscopic so it absorbs moisture from the air all the time. If you only bleed the dirty fluid out from the wheel cylinders and calipers (without properly flushing the reservoir) all you are doing is leaving high water content brake fluid in the system.
You can change the fluid without sucking the old fluid out of the reservoir but you need twice the fluid because you are having to flush the reservoir as well as the brake lines.
You can gravity bleed but it takes a long time. You can vacuum bleed as well but if you get too excited whilst vacuum bleeding you can suck air into the line so after vacuum bleeding I've found it best to leave the nipple open and let it gravity bleed for a few minutes to let the air out (you can sometimes see bubbles come out, which is not good) . You can pedal bleed by opening the nipple, pumping brake pedal to the floor and holding, tightening the nipple then releasing the pedal (and repeating over and over) but some times on high mileage cars you can get master cylinder trouble after this.
The best way is pressure bleeding. If you are flushing the reservoir you'll have to send about 1 litre through the first nipple (depending how much fluid your reservoir takes) to properly rinse the old fluid out of the reservoir and out of the system and then bleed the rest normally so you'll be pumping fresh fluid to the other lines.
start with the nipple furthest away from the master cylinder first.
You can change the fluid without sucking the old fluid out of the reservoir but you need twice the fluid because you are having to flush the reservoir as well as the brake lines.
You can gravity bleed but it takes a long time. You can vacuum bleed as well but if you get too excited whilst vacuum bleeding you can suck air into the line so after vacuum bleeding I've found it best to leave the nipple open and let it gravity bleed for a few minutes to let the air out (you can sometimes see bubbles come out, which is not good) . You can pedal bleed by opening the nipple, pumping brake pedal to the floor and holding, tightening the nipple then releasing the pedal (and repeating over and over) but some times on high mileage cars you can get master cylinder trouble after this.
The best way is pressure bleeding. If you are flushing the reservoir you'll have to send about 1 litre through the first nipple (depending how much fluid your reservoir takes) to properly rinse the old fluid out of the reservoir and out of the system and then bleed the rest normally so you'll be pumping fresh fluid to the other lines.
start with the nipple furthest away from the master cylinder first.
Originally Posted By: ac_tc
Vacum bleeding is a tool that should be used wizely...
they can pull air into the brakes by the seals and you will get a soft and spoongy pedal- not good.
Originally Posted By: riggaz
You can vacuum bleed as well but if you get too excited whilst vacuum bleeding you can suck air into the line.
It's not possible for air to travel in opposite direction with brake fluid.
Let say brake system is "A", bleeder valve is "B" and vacuum reservoir is "C".
You create a vacuum with C, brake fluid will flow from A through B into C, there is slight leak at bleeder valve B so some air bubbles will be sucked into C, as it can be observed in the suction tube between B and C.
Now, how any air can travel from B into A, while brake fluid is being sucked from A into C through B ? It is against the law of physic.
I used Mityvac to bleed brake system of my cars more than once each car, never had any soft pedal after bleeding.
Vacum bleeding is a tool that should be used wizely...
they can pull air into the brakes by the seals and you will get a soft and spoongy pedal- not good.
Originally Posted By: riggaz
You can vacuum bleed as well but if you get too excited whilst vacuum bleeding you can suck air into the line.
It's not possible for air to travel in opposite direction with brake fluid.
Let say brake system is "A", bleeder valve is "B" and vacuum reservoir is "C".
You create a vacuum with C, brake fluid will flow from A through B into C, there is slight leak at bleeder valve B so some air bubbles will be sucked into C, as it can be observed in the suction tube between B and C.
Now, how any air can travel from B into A, while brake fluid is being sucked from A into C through B ? It is against the law of physic.
I used Mityvac to bleed brake system of my cars more than once each car, never had any soft pedal after bleeding.
Originally Posted By: riggaz
You can pedal bleed by opening the nipple, pumping brake pedal to the floor and holding, tightening the nipple then releasing the pedal (and repeating over and over) but some times on high mileage cars you can get master cylinder trouble after this.
In fact it's almost guaranteed. The fluid in the reservoir absorbs moisture, this sits in the back of the master cylinder bore that never normally gets touched because you normally only get about 50mm of pedal travel. This un-touched bit of bore gets some slight corrosion from the old, wet fluid. It also accumulates any grunge or dirt from decaying parts, and the first time you floor the pedal the piston sweeps past all this grit and tears the seal to pieces.
If you want to pedal bleed, work out how far you push the pedal in your worst case emergency stops and put a wooden block behind it to stop you pressing it any further, then pedal bleed. You can test for damage by pumping the vacuum out of the booster with the engine off and standing on the pedal. If you've got a damaged seal, it will slowly (where slowly might mean 10 seconds or it might mean a minute) drop to the floor.
This is a common injury on any car more than a couple of years old, and any car that has not had regular fluid flushes. It's easily prevented however.
You can pedal bleed by opening the nipple, pumping brake pedal to the floor and holding, tightening the nipple then releasing the pedal (and repeating over and over) but some times on high mileage cars you can get master cylinder trouble after this.
In fact it's almost guaranteed. The fluid in the reservoir absorbs moisture, this sits in the back of the master cylinder bore that never normally gets touched because you normally only get about 50mm of pedal travel. This un-touched bit of bore gets some slight corrosion from the old, wet fluid. It also accumulates any grunge or dirt from decaying parts, and the first time you floor the pedal the piston sweeps past all this grit and tears the seal to pieces.
If you want to pedal bleed, work out how far you push the pedal in your worst case emergency stops and put a wooden block behind it to stop you pressing it any further, then pedal bleed. You can test for damage by pumping the vacuum out of the booster with the engine off and standing on the pedal. If you've got a damaged seal, it will slowly (where slowly might mean 10 seconds or it might mean a minute) drop to the floor.
This is a common injury on any car more than a couple of years old, and any car that has not had regular fluid flushes. It's easily prevented however.
Originally Posted By: HTSS_TR
Originally Posted By: ac_tc
Vacum bleeding is a tool that should be used wizely...
they can pull air into the brakes by the seals and you will get a soft and spoongy pedal- not good.
It's not possible for air to travel in opposite direction with brake fluid.
Now, how any air can travel from B into A, while brake fluid is being sucked from A into C through B ? It is against the law of physic.
The top posts you quoted states it clearly. The brake system is designed to hold pressure (lots of it). When subjected to a vacuum it is possible (not common, but possible) for air to be sucked past a seal in a caliper or piston. Air is considerably lower in viscosity than brake fluid, and the seals are designed to hold liquid and specifically in one direction.
Just because it's never happened to you does not mean it can't and doesn't happen. I had it happen, and I now pressure bleed instead.
Originally Posted By: ac_tc
Vacum bleeding is a tool that should be used wizely...
they can pull air into the brakes by the seals and you will get a soft and spoongy pedal- not good.
It's not possible for air to travel in opposite direction with brake fluid.
Now, how any air can travel from B into A, while brake fluid is being sucked from A into C through B ? It is against the law of physic.
The top posts you quoted states it clearly. The brake system is designed to hold pressure (lots of it). When subjected to a vacuum it is possible (not common, but possible) for air to be sucked past a seal in a caliper or piston. Air is considerably lower in viscosity than brake fluid, and the seals are designed to hold liquid and specifically in one direction.
Just because it's never happened to you does not mean it can't and doesn't happen. I had it happen, and I now pressure bleed instead.
I've got both systems (mity vac and power bleeder) and prefer my power bleeder any day. The only down fall is the up front cost (esp with all the different MC adapters) and the clean up when finished (I am anal about cleaning it up after every use) but it is hands down a quicker and more efficient system. I just did a full sized truck last night after replacing a blown rear line. The owner drove the truck 2 days prior to bringing it over and it was full of air. Pressured the system up to 12-15 psi, cracked a couple of fittings at the abs module (the highest point in the system), went around to all 4 wheels with a hose and a catch can and cracked them one at a time. Bleeding took no more than 15 minutes from start to finish and that was taking my time. Brakes worked flawlessly when I was finished.
Originally Posted By: Brad_C
Originally Posted By: riggaz
You can pedal bleed by opening the nipple, pumping brake pedal to the floor and holding, tightening the nipple then releasing the pedal (and repeating over and over) but some times on high mileage cars you can get master cylinder trouble after this.
In fact it's almost guaranteed. The fluid in the reservoir absorbs moisture, this sits in the back of the master cylinder bore that never normally gets touched because you normally only get about 50mm of pedal travel. This un-touched bit of bore gets some slight corrosion from the old, wet fluid. It also accumulates any grunge or dirt from decaying parts, and the first time you floor the pedal the piston sweeps past all this grit and tears the seal to pieces.
If you want to pedal bleed, work out how far you push the pedal in your worst case emergency stops and put a wooden block behind it to stop you pressing it any further, then pedal bleed. You can test for damage by pumping the vacuum out of the booster with the engine off and standing on the pedal. If you've got a damaged seal, it will slowly (where slowly might mean 10 seconds or it might mean a minute) drop to the floor.
This is a common injury on any car more than a couple of years old, and any car that has not had regular fluid flushes. It's easily prevented however.
Pumping the pedal to the floor is exactly how I did my brakes.
Is there any way to reverse the damage doing another system flush? Help!
Originally Posted By: riggaz
You can pedal bleed by opening the nipple, pumping brake pedal to the floor and holding, tightening the nipple then releasing the pedal (and repeating over and over) but some times on high mileage cars you can get master cylinder trouble after this.
In fact it's almost guaranteed. The fluid in the reservoir absorbs moisture, this sits in the back of the master cylinder bore that never normally gets touched because you normally only get about 50mm of pedal travel. This un-touched bit of bore gets some slight corrosion from the old, wet fluid. It also accumulates any grunge or dirt from decaying parts, and the first time you floor the pedal the piston sweeps past all this grit and tears the seal to pieces.
If you want to pedal bleed, work out how far you push the pedal in your worst case emergency stops and put a wooden block behind it to stop you pressing it any further, then pedal bleed. You can test for damage by pumping the vacuum out of the booster with the engine off and standing on the pedal. If you've got a damaged seal, it will slowly (where slowly might mean 10 seconds or it might mean a minute) drop to the floor.
This is a common injury on any car more than a couple of years old, and any car that has not had regular fluid flushes. It's easily prevented however.
Pumping the pedal to the floor is exactly how I did my brakes.
If you need me to explain to you why the fluid in the calipers gets hotter than anywhere else, you probably shouldn't be working on vehicles.
Here is a hint: your brake fluid is a closed loop system meaning it does not circulate. The fluid that's in the calipers for the most part is the same fluid that's been in there since the day it was put in.
As to the moisture comment, water is heavier than brake fluid, and being the caliper/ wheel cylinder is at the lower end of the brake system, that is where you will find any moisture first. I mentioned in my previous post that to get all the contaminated fluid out of the calipers they need to be removed and evacuated with a C clamp, and this is exactly why. Any contaminants/moisture will be settled at the bottom and will not all be pushed out the bleeder at the top.
Here is a hint: your brake fluid is a closed loop system meaning it does not circulate. The fluid that's in the calipers for the most part is the same fluid that's been in there since the day it was put in.
As to the moisture comment, water is heavier than brake fluid, and being the caliper/ wheel cylinder is at the lower end of the brake system, that is where you will find any moisture first. I mentioned in my previous post that to get all the contaminated fluid out of the calipers they need to be removed and evacuated with a C clamp, and this is exactly why. Any contaminants/moisture will be settled at the bottom and will not all be pushed out the bleeder at the top.
In vehicles that get serviced regularly or even semi regular there won't be. But in vehicles that don't get serviced there absolutely will be moisture to some degree. I've seen enough rusted caliper pistons to verify this.
Why do you think every manufacturer has a service interval for brake fluid? Degraded brake fluid is no joke, scam, or folley. It is THE most important system on a vehicle and yet it is also one of the most over looked.
Why do you think every manufacturer has a service interval for brake fluid? Degraded brake fluid is no joke, scam, or folley. It is THE most important system on a vehicle and yet it is also one of the most over looked.
Originally Posted By: jrmason
In vehicles that get serviced regularly or even semi regular there won't be. But in vehicles that don't get serviced there absolutely will be moisture to some degree. I've seen enough rusted caliper pistons to verify this.
Why do you think every manufacturer has a service interval for brake fluid? Degraded brake fluid is no joke, scam, or folley. It is THE most important system on a vehicle and yet it is also one of the most over looked.
Not all manufactures have a brake fluid interval. GM for one. No recommended change for my Silverado (though I will still do it anyways).
In vehicles that get serviced regularly or even semi regular there won't be. But in vehicles that don't get serviced there absolutely will be moisture to some degree. I've seen enough rusted caliper pistons to verify this.
Why do you think every manufacturer has a service interval for brake fluid? Degraded brake fluid is no joke, scam, or folley. It is THE most important system on a vehicle and yet it is also one of the most over looked.
Not all manufactures have a brake fluid interval. GM for one. No recommended change for my Silverado (though I will still do it anyways).
Originally Posted By: 2civics
Sorry...rewind. My car only has 27k miles on it. Does that play into whether damage was done or not?
Yeah, it does. Do the test I suggested. Engine off, pump brakes until you lose vacuum assist and pedal goes hard then put lots of pressure on the pedal and see if it sinks to the floor over 10-60 seconds.
If it stays up then no problem. If it doesn't then its new M/C time.
Sorry...rewind. My car only has 27k miles on it. Does that play into whether damage was done or not?
Yeah, it does. Do the test I suggested. Engine off, pump brakes until you lose vacuum assist and pedal goes hard then put lots of pressure on the pedal and see if it sinks to the floor over 10-60 seconds.
If it stays up then no problem. If it doesn't then its new M/C time.
Originally Posted By: Vikas
If it gets so hot, why does it have the moisture?
The moisture gets in at the caliper end _slowly_ as the brakes are used. Each cycle of the piston has the potential to let a gnat's worth of moisture in back past the seal. It's tiny and insignificant in itself but when you look at the amount of times your pistons are cycled in a couple of years you wind up with enough moisture to be a corrosion risk and lower the boiling point of the fluid. We all know moisture also makes its way into the M/C so diffuses its way through the system also.
Heat is a different matter entirely and has nothing to do with moisture ingress other than to say the more moisture in the fluid, the more susceptible it is to boiling under hot conditions.
Heat can also lead to a gradual breakdown of the fluid which is why some racers do a flush after every race day (or couple).
If it gets so hot, why does it have the moisture?
The moisture gets in at the caliper end _slowly_ as the brakes are used. Each cycle of the piston has the potential to let a gnat's worth of moisture in back past the seal. It's tiny and insignificant in itself but when you look at the amount of times your pistons are cycled in a couple of years you wind up with enough moisture to be a corrosion risk and lower the boiling point of the fluid. We all know moisture also makes its way into the M/C so diffuses its way through the system also.
Heat is a different matter entirely and has nothing to do with moisture ingress other than to say the more moisture in the fluid, the more susceptible it is to boiling under hot conditions.
Heat can also lead to a gradual breakdown of the fluid which is why some racers do a flush after every race day (or couple).
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