Corolla 2001 brakes bleeding

gravity bleeding will work fine and it's best to bleed the whole system at the wheels. you shouldn't have to crack the lines connected to the brake master. I've done it many times with all the brake jobs done in the past. just remember to keep checking the master cylinder reservoir to make sure is isn't going dry again or you're doing double work. work 1 wheel at a time, cracking the bleeder screw and let the fluid drip. let it drip until clean fluid emerges. also, keep the cap on the master loose or off so a vacuum isn't created as the fluid is drained. note: since one chamber of the master went dry, as the fluid is dripping from the first bleeder screw you've opened. tap the end of the master cylinder with a hammer to help dislodge any air bubbles trapped inside the master. just don't pound on it since it is a cast aluminum body. once you've bled all 4 wheels, pump the brake pedal a few times, making sure not to bottom out the pedal (or you risk killing the master cylinder). this will cause the caliper pistons caliper pistons to move back into their proper position if they were compressed while changing pads. it will also help to work loose any air bubbles that may have remained trapped in the brake system. now, just bleed all 4 wheels again to get the remaining bubbles out and you should be in top shape!

"Tom Waga" wrote in message news:B16sf.84875$2k.32255@pd7tw1no...

I did the job using gravity method. There was lots of bubbles flowing out with fluid. I did not open the lines at the master.

After it looked OK I decided to re-check it with pedal/helper method. Front line (the one I opened at the wheel cylinder) did not released any more bubbles but the rear diagonal one had very fine bubbles coming out for some time. I am not sure is it because with gravity flow the liquid velocity is to slow to remove all the bubbles or I just cleared the line not long enough?

I used the block of wood to restrict travel of the pedal while pumping brakes and opening the nipples but I just wonder if that was necessary. The reason is that although I haven never changed brake fluid till now (5 years time) but every time I changed brake pads (every 50 000 KM) I had to press brake pedal all the way to the floor to bring the pistons to the pads after they were compressed (pistons). Wouldn't that remove any gunk from inside of the master cylinder?

| > 1. Since only one chamber of reservoir was emptied will it be OK if I | > bleed | > only part of the system which was emptied in this case the driver back and | > next passenger front (in that order - I understand Corolla has a diagonal | > brake system) ? | >

| > 2. Should I bleed emptied part of master cylinder by loosing the line at | > the | > mc or any air will be pushed out when brakes are bled, and what about | > front/rear distribution block? | >

| > 3. Instead of using helper/pedal method can I use gravity method by | > opening | > the bleeding nipple with hose on the end submerged in bottle with fluid | > (it | > will take longer but not require helper)? | >

| >

| >

| |

you were very lucky in the past when the brake pedal was bottomed out. during the course of normal driving/braking, each time the brake pedal is depressed, the piston in the master cylinder only travels a certain distance due to the resistance caused by the pads and shoes doing their job (making contact with the rotor & drum). since the master cylinder piston rod/seal cups continually travel over a specific area due to the hydraulic pressure, gunk/junk often builds up in the area not cleared by the seal. in turn, pitting usually occurs in aluminum bodied masters where the gunk/junk settles (steel bodied masters usually aren't affect as often). when the seal travels over the area with the gunk/junk, the seal can be damaged. also, the gunk/junk usually causes pitting which is visible when the area is cleared. often the damaged seal isn't noticed under heavy braking because the seal expands rapidly, pushing on the brake fluid. the damage seal usually shows itself in heavy traffic or gentle braking, where the seals aren't so expanded and allow brake fluid to by-pass the seal, which will cause the pedal to start going to the floor. at that point, most people panic and push the pedal hard which usually causes sufficient hydraulic pressure to fully expand the seal and stop the vehicle. then when the foot pressure is let up, the process happens all over again. many times the driver will pump the pedal and it will seem hard and firm again and they can't figure out what's going on.

as far as your question about the junk in the caliper being dislodged and flushed out when the bleeder is opened...sorry, it wont happen. there may be some loose junk drifting around in the fluid and that type of junk will come out when bleeding the brakes, but there's more junk and varnish that remains stuck to the inside of the caliper. the caliper piston rides on the caliper piston seal and doesn't make contact with the caliper body, except for the bottom of the piston when it is bottomed out in the caliper. all that crap in the caliper body will cause pitting, which isn't much of a problem as long as it doesn't build up by the seal grove. when the junk does build up by the seal grove, it affects the way the seal operates and will often lead to sticking pistons and rapid wear of the brake pads, not to mention pulling when braking and brake drag.

FYI...the gunk/junk also builds up in the wheel cylinders and will also cause corroding and pitting. it usually manifests its self by leaking in the brake drum. you can do a simple check when checking the rear brakes (wheels/drums off). just use a small screw driver or pinch the dust boot on the wheel cylinder to lift a small area. if very little fluid leaks out, it's ok (normal weeping). if it gushes out, it's a sign the wheel cylinder is starting to go and it may not be too long before it starts to actually leak, soaking the rear brakes.

"Tom Waga" wrote in message news:F8psf.201126$ki.81970@pd7tw2no...

forgot to mention, the critical sealing surface in the caliper (besides having a clean/clear piston seal grove) is the caliper piston. the piston can have some very minor pitting, as long at the pitting isn't large enough to cause fluid to by-pass the seal, but eventually it will need to be replaced and will only save you money in the short term. a pitted or badly scored caliper piston should be replaced when doing the brake job the first time. not a few months later.

as for my back ground, I worked as a brake tech many years ago, on all makes and types of passenger cars & trucks. personally (my opinion only), I don't care for preloaded calipers since I usually ended up rebuilding them because they weren't done properly at the rebuilder (in most cases, I found junk left in the caliper seal grove which would cause the seal to hang up). did it all from complete brake jobs (including overhauls/rebuilds), machining drums and rotors off the vehicle and machining rotors on vehicles (my preference since I'd try to get the run-out to .000). if the tech could and would take the time to do the job right the 1st time, the chance of the vehicle returning for a problem would be minimal until the lining needed changing again. of course, the driver would have to do their part and not abuse their brakes. I had a lady once who returned the day after a complete brake job. she complained of an odd smell and the car was hard to stop. once the wheels were pulled, the problem was obvious. the rotors were literly blue with hard spots. turned out, the lady wanted to help break-in her new brakes so she rode the brake pedal all the way home (about 12 miles). fortunately the rotors could be resurfaced within toleranced and the hard spots came out. brake linings were replaced and the driver instructed on what not to do. don't remember ever hearing from her again after that.

What would be a time period needed to deposit dangerous enough gunk layer on the inside of master cylinder (approx)?

| > After it looked OK I decided to re-check it with pedal/helper method. | > Front | > line (the one I opened at the wheel cylinder) did not released any more | > bubbles but the rear diagonal one had very fine bubbles coming out for | > some | > time. I am not sure is it because with gravity flow the liquid velocity is | > to slow to remove all the bubbles or I just cleared the line not long | > enough? | >

| > I used the block of wood to restrict travel of the pedal while pumping | > brakes and opening the nipples but I just wonder if that was necessary. | > The | > reason is that although I haven never changed brake fluid till now (5 | > years | > time) but every time I changed brake pads (every 50 000 KM) I had to press | > brake pedal all the way to the floor to bring the pistons to the pads | > after | > they were compressed (pistons). Wouldn't that remove any gunk from inside | > of | > the master cylinder? | >

| >

| >

| > | > 1. Since only one chamber of reservoir was emptied will it be OK if I | > | > bleed | > | > only part of the system which was emptied in this case the driver back | > and | > | > next passenger front (in that order - I understand Corolla has a | > diagonal | > | > brake system) ? | > | >

| > | > 2. Should I bleed emptied part of master cylinder by loosing the line | > at | > | > the | > | > mc or any air will be pushed out when brakes are bled, and what about | > | > front/rear distribution block? | > | >

| > | > 3. Instead of using helper/pedal method can I use gravity method by | > | > opening | > | > the bleeding nipple with hose on the end submerged in bottle with | > fluid | > | > (it | > | > will take longer but not require helper)? | > | >

| > | >

| > | >

| > | | > | | >

| >

| |

poorly maintained vehicles, possibly 5 years, or less, dependant on driving conditions (lots of water crossing or driving with water up to the axles). well maintained vehicles, 7+ years or longer.

gunk build-up would be dependant on how often brake fluid is flushed through the system and the moisture in the environment. brake fluid is hydroscopic, meaning it absorbs moisture. the moisture can be absorbed through the rubber brake hoses, especially if they're cracked on the outer surface, some moisture is absorbed when the cap from the master is removed for a prolonged period of time (like all day), and moisture is absorbed even through the seals in the calipers and wheel cylinders and even through the rubber seal for the master cylinder cap. (many people aren't even aware there are rubber brake hoses some where in the system for the rear brakes, since they aren't easily visible until the vehicle is lifted). if you live in a drier climate and flush the brake fluid annually, gunk build-up should be minimal. a good indicator is the color of the old fluid being flushed out. at its worst, the color is a dark amber meaning there's a strong probability that gunk and varnish is accumulating some where within the brake system. if the fluid being flushed out is a light amber to clear, you probably don't have much to worry about.

One would wonder why isn't there a scheduled brake fluid replacement/brake line flush procedure included in the service manual since it can induce such a negative effect on the master cylinder and brake lines?

| >

| > | > After it looked OK I decided to re-check it with pedal/helper method. | > | > Front | > | > line (the one I opened at the wheel cylinder) did not released any | > more | > | > bubbles but the rear diagonal one had very fine bubbles coming out for | > | > some | > | > time. I am not sure is it because with gravity flow the liquid | > velocity | > is | > | > to slow to remove all the bubbles or I just cleared the line not long | > | > enough? | > | >

| > | > I used the block of wood to restrict travel of the pedal while pumping | > | > brakes and opening the nipples but I just wonder if that was | > necessary. | > | > The | > | > reason is that although I haven never changed brake fluid till now (5 | > | > years | > | > time) but every time I changed brake pads (every 50 000 KM) I had to | > press | > | > brake pedal all the way to the floor to bring the pistons to the pads | > | > after | > | > they were compressed (pistons). Wouldn't that remove any gunk from | > inside | > | > of | > | > the master cylinder? | > | >

| > | >

| > | >

| > | > | > 1. Since only one chamber of reservoir was emptied will it be OK | > if | > I | > | > | > bleed | > | > | > only part of the system which was emptied in this case the driver | > back | > | > and | > | > | > next passenger front (in that order - I understand Corolla has a | > | > diagonal | > | > | > brake system) ? | > | > | >

| > | > | > 2. Should I bleed emptied part of master cylinder by loosing the | > line | > | > at | > | > | > the | > | > | > mc or any air will be pushed out when brakes are bled, and what | > about | > | > | > front/rear distribution block? | > | > | >

| > | > | > 3. Instead of using helper/pedal method can I use gravity method | > by | > | > | > opening | > | > | > the bleeding nipple with hose on the end submerged in bottle with | > | > fluid | > | > | > (it | > | > | > will take longer but not require helper)? | > | > | >

| > | > | >

| > | > | >

| > | > | | > | > | | > | >

| > | >

| > | | > | | >

| >

| |

more than likely it comes down to the almighty $. if vehicle owners kept on top of everything, then parts wouldn't wear as fast and parts wouldn't need replacing or rebuilding as often. allows them to charge a fair amount for something that isn't really difficult to do. I remember labor charges for a complete brake job for an American car (rebuilding calipers/wheel cylinders, resurfacing rotors & drums and bleeding the hydraulic system, installing new pads/shoes) costing $120 + parts charges. I'd make about $2.40 off the labor charge (plus my hourly wage) and it took any where from 1/2 hour to 45 minutes to do the actual work. you do the math for an 8 hour day. that's why I got out of that line of work. busting your rear for peanuts while the shop makes the big bucks.

BTW... the shop also used to charge $160 to do only the front brakes (labor only) on a front wheel drive car without hubless rotors (older imports). even though the rotors were machined with an on-the-car lathe. usually the machining would take about 1/2 hour and the calipers were rebuilt while the rotors were being cut.