Major problems. This is the textbook way to do it and it's how I used to teach the "right" way to do it. That had to be followed up with, "if you do it this way for an employer, you'll be reprimanded the first time, and fired the second time, for multiple reasons.
First of all. You're paying for our time at around $100.00 per hour. Our bosses don't like having to charge that much but you can thank government red tape, the EPA, and OSHA for those high bills. To bleed the brakes this way requires two people and well over an hour a piece. No one wants to pay $200.00 just for bleeding the brakes on top of whatever other repairs made bleeding necessary. This job not only CAN be done by one person, it MUST be done by one person.
The next problem is that turkey baster. Yes, that's what we would use, if there even was one in our shop. On the very slim chance there is, no professional would ever risk using it because we wouldn't know where it has been. If it was laying somewhere where the slightest hint of petroleum product got on it, like engine oil, transmission fluid, power steering fluid, or axle grease, dipping that into the brake fluid will contaminate the fluid, and that is a REAL serious issue. Every year I did a demonstration for my students where I put fresh clean brake fluid in two beakers, and a rear-wheel cylinder lip seal into each one. In one beaker I added one drop of power steering fluid. By the end of the week that seal had grown about ten percent in size and was real soft and mushy. That is what will happen to every rubber part in the entire hydraulic system that contacts brake fluid. At that point the only proper repair is to remove the master cylinder, four rubber flex hoses, front calipers, rear wheel cylinders, combination valve, and the height-sensing proportioning valve that most trucks and minivans use. Next you flush all the steel lines with brake parts cleaner, and dry them, then you install all new rubber parts. If you have anti-lock brakes, the hydraulic controller gets replaced too because that is full of o-rings and seals.
If any rubber part is overlooked, the contamination will leach out of it and recontaminate all the new parts and you get to start all over. I was involved with three cars with contaminated brake fluid. One was an old '59 Edsel I had just bought like that, and one was a car at the shop I worked at. The third one went to the salvage yard because the cost of repair exceeded the value of the car.
The idea behind sucking the fluid out is to avoid having to run it through the system and out by the wheels. Big deal. If you're replacing hoses, calipers, and / or wheel cylinders, that fluid will be running out anyway. (A simple truck to avoid that is to place a stick from the front seat to the pedal to hold the pedal down just an inch. The lip seals will block the fluid ports and keep the fluid in the reservoir).
As a point of interest, you'll often need to pop the rubber bladder seal back into the reservoir cap. Experienced professionals will wash their hands with soap and water before doing that to avoid getting fingerprint grease on that rubber part and when working with any other rubber parts in the system.
That bladder seal is a good indicator of fluid contamination too. It will be blown up and mushy, and you won't be able to get it to stay in the cap. The lip seals will do the same thing and they'll grow past the fluid return ports and block them. This is one of the most common causes of the complaint of locking brakes. They get warm from normal braking and that causes the fluid to expand. Since it's trapped and can't flow back into the reservoir, pressure builds by itself and the brakes apply harder. That makes the fluid hotter, and the brakes self-apply harder until the car won't even move.
The next thing I take issue with is having a helper push the brake pedal all the way to the floor! The only time it is okay to do that is when it's a new / rebuilt master cylinder or it's less than about a year old. After that you have about a 50 percent chance of destroying the master cylinder. Under normal operation the pedal only goes about halfway down. The pistons and lip seals in the master cylinder never run in the lower halves of their bores, so that's where crud and corrosion build up. Pushing the brake pedal all the way down runs the lip seals over that crud and can rip them. After that, the fluid will bypass the seals rather than get pushed down to the wheels. The symptom at first will be a slowly-sinking pedal as you hold steady pressure on it. That may not show up right away. It could take a few days, but how do you explain to your customer that you just performed a normal maintenance brake job, but now their master cylinder is bad?
The proper procedure is to pretend there's a block of wood under the pedal and never push the pedal more than halfway down. This is a big enough issue that when a customer comes in with a ruptured hose, we assume they pushed the pedal to the floor when they were surprised by the leak, and we include a rebuilt master cylinder in the estimate. A typical rebuilt master cylinder will cost less than fifty bucks, and I can replace one in less than a half hour with no need at all to bleed at the wheels or even remove them. No professional will risk his reputation by assuming the master cylinder is okay after that type of incident. We usually leave the decision to replace it up to the car owner if it isn't causing a problem at the moment, but only after we've given them this explanation.
The next issue applies specifically to GM front-wheel-drive vehicles. A lot of people run into a problem after pushing the brake pedal over halfway and they assume they damaged the master cylinder, even one they just replaced. The next one does the same thing. The hydraulic system is a "split-diagonal" system, meaning the left front and the right rear are on the same hydraulic circuit. That insures if there's a leak anywhere, you'll still have one working front brake. Chrysler started that in the late '70s, and by modifying a non-adjustable alignment angle called "scrub radius" you will not only not get a brake pull, you won't even see the steering wheel move when you apply the brakes. If that happened on an older rear-wheel-drive car, hitting the brakes with only one front one working would tear the steering wheel out of your hands. On your vehicle you will see a little twitch in the steering wheel, but that will be the only symptom.
The reason I started to describe this is you have another issue to contend with that only applies to GM front-wheel-drive vehicles. Imagine there's a little teeter totter inside the master cylinder, and on each end there's a little rubber plug that fits into the ports the fluid travels through. When both halves of the hydraulic system are working normally, that teeter totter is balanced regardless how far or hard you push the brake pedal. Things change when you have the bleeder screws open. If you're lucky you'll get brake fluid at all four wheels, then, as you close the bleeders and continue the procedure, at some point pressure will start to build at one pair of wheels. That will trip that teeter totter and one of the rubber plugs will block the other pair of ports. At that point no fluid will flow to those two wheels regardless how hard you stomp on the pedal. If you don't notice the lack of fluid flow, you will think everything is normal. The brake pedal will feel normal. It will not go further down to the floor than normal, and all you'll see is that little twitch in the steering wheel. A few drivers will notice the longer distances needed to stop the vehicle, but most people figure out there's a problem when their new brake pads start grinding on one front wheel after a month or two, and the pads on the other side look like brand new. That's because the pads on only one side are doing all the stopping.
This is actually a nice idea because if your vehicle springs a leak, you won't lose all the brake fluid and you'll still be able to stop. The problem is knowing how to correct this, which is pretty easy. The second problem is the only other indication there's a problem is the red "Brake" warning light will be on. Too bad a lot of people ignore it. That light also turns on when the brake fluid level is low in the reservoir, (on vehicles that have that option), so some people just add fluid, then ignore the problem.
This brings me to the last concern. That is the order you bleed the wheels. The proper order depends on who you ask or which book you're reading. Some people say to do the right rear first so you get the largest percentage of air out of the system with that one wheel. Some say to do the left front first because that one takes the least time and effort to get the line to one wheel full of fluid. The truth is, it doesn't matter because ultimately you're going to remove all the air from the system. What difference does it make where the last ounce of air comes from? The reason people believe there is a specific order is they did it once this way and that teeter totter didn't move and cause problems. The fact is, you prevent that valve from moving and blocking two ports by simply, ... Never pushing the pedal more than halfway to the floor!
So now, even for the few people who don't believe me about damaging the master cylinder on any car, there is a valid reason to not push the pedal over halfway on GM products.
I used to work for a mass merchandiser with an auto repair shop, and in the '80s it was much more necessary than today to rebuild wheel cylinders and calipers with every brake job. We had a bleeder ball" that allowed us to force brake fluid into the master cylinder under a few pounds of pressure to aid in bleeding. Some people still liked to pedal-bleed with a helper, but I had the best luck with "gravity-bleeding", and that's what I recommend you do.
It was common for me to rebuild everything on one side of the car, and my work partner to do the other side. We'd start at 8:00 a.M, and by 10:00 everything was done, the bleeder screws were open, the fluid was filled, and the reservoir cap was left just loose enough so no vacuum would build up when the fluid ran out. We left for our scheduled 15-minute brake, but then one of us would run back in five minutes and find fluid dripping from one bleeder screw. We'd close that one, then fluid would be dripping from a second wheel a few minutes later. Close that one, then wait for the next one to start dripping, then close it. By the time we came back from break, all the wheels were bled. The last step was to "irritate" the break pedal a little, as in push it less than an inch a few times. That would cause the few tiny remaining bubbles to wash into the wheel cylinders and calipers. Pop the bleeder screws open once more for a couple of seconds to give those bubbles their freedom, and the bleeding was done.
Also, when new front pads are installed, you have to push the pistons back into the calipers. Once the bleeding is done, you have to work the brake pedal repeatedly to push those pistons back out. That will also wash any remaining bubbles into the calipers where they will pop out when you open the bleeder screws one last time. Remember again, k when doing this few-second step, don't push the pedal more than halfway to the floor.
Now for the secret to centering that teeter totter so fluid will flow again to those two wheels, pick one wheel where fluid isn't flowing and open that bleeder screw. I prefer the front wheel because it's easier to see the bleeder screw. Loosen the cover on the reservoir, then, using a rubber-tipped air nozzle, give a quick, short burst of compressed air into that bleeder screw, then let it gravity-bleed again. You don't want to shoot air all the way back to the master cylinder because you'll just have that much more to bleed out again. I just tap the nozzle handle with my fist, then, typically fluid will come running out within a few seconds.
As a final comment, I'm going to tell you more than I know. Normally when this problem occurs the pistons are still fully retracted into the calipers, and / or there's almost no room between the piston and pad because you just put new thick pads in there, but if you should find the piston is out far enough AND you can pry it back in with a screwdriver, that might be sufficient fluid flow to reset that valve. I've never tried this so I don't know if it will work. I've always had access to compressed air, and that has never failed to work.
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Sunday, March 29th, 2015 AT 2:29 AM
