It depends on the type of brake job you performed. If you slapped in new pads and machined the rotors, no air will have entered the hydraulic system, so no bleeding is necessary. The only concern is you needed to push the pistons into the calipers to make room for those new, thicker pads. I do that by prying them in with a flat-blade screwdriver before I unbolt the calipers. If you're strong, you can press the pistons in by hand. Some people do that with a C-clamp after the calipers have been removed. If that is the only way to get the pistons retracted, there is debris built up behind those pistons, and they're going to stick, usually causing a failure to release, and overheated pads and rotors. Years ago it was customary to rebuild calipers with every brake job, but today, professionally-rebuilt calipers with a warranty are so inexpensive that rebuilding them on site is not a good value.
The next concern, regardless if you rebuilt or replaced the calipers, or if you just retracted the pistons, is once the job is completed, the last step is to run the pistons out to adjust them. We do that by pressing the brake pedal repeatedly until a solid pedal is reached. This is where the next problem can develop. Crud and corrosion develop in the lower halves of the bores in the master cylinder where the lip seals don't normally travel. If you press the brake pedal all the way to the floor for any reason, the seals will be ripped as they ride over that corrosion. That results in an "internal" leak and a slowly-sinking brake pedal. That commonly takes two or three days to show up. Rebuild kits are available for master cylinders, but every time I've checked, those kits cost as much as a professionally rebuilt master cylinder. Rebuilt master cylinders need to be bench-bled before they're installed, but in doing that, it is okay to push the pistons all the way. It takes roughly a year before that internal corrosion begins to form.
To prevent that damage to the master cylinder, never push the brake pedal more than halfway to the floor. If you do replace a part that opens the hydraulic system, you don't necessarily have to bleed everything. For example, if you replace the left front rubber flex hose, that is the only wheel where you need to bleed.
Another potential problem can be caused by leaving the hydraulic circuit open for a long period of time, then the brake fluid runs out of the reservoir, leaving it empty. Now all that air has to be bled out, but if your vehicle has anti-lock brakes, most models have chambers in the hydraulic controller where air pools and won't bleed out. For those, you need a scanner that can tell the ABS Computer to open two valves so that air will be expelled, then it can be bled out at the wheels. The scanners will walk you through that procedure. On most models it takes much less than a full minute to do that part of the procedure.
If you do have to leave a hydraulic circuit open for a long time, such as when you return to the parts store to get the correct part, place a stick between the driver's seat and the brake pedal to hold that pedal down about an inch. That will move the lip seals past the fluid return ports. Gravity won't be strong enough to pull brake fluid out of the reservoir. It won't run empty, no air will get in the fluid, and all you have to do is add is little brake fluid, if necessary.
By the way, when you have new pads installed, the fluid level in the reservoir should be close to the "full" or top line. As the pads wear, the pistons move out to self-adjust. Brake fluid fills in behind them, so it's normal for the level to drop in the reservoir. We never top that off during other services, like il changes. If brake fluid is added, the next time the pistons get pushed in for new pads, the fluid will overflow, creating a mess and damage to painted surfaces.
All manufacturers have a recommended brake fluid flush interval, but few people pay any attention to that because these systems are so trouble-free. Brake fluid naturally turns dark after being hot many times. We flush the fluid to get the moisture out that it loves to absorb out of the air. That moisture boils at 212 degrees which is far lower than brake fluid's boiling point of well over 400 degrees. With excessive moisture in the brake fluid, that fluid can boil and vaporize under normal driving conditions, leading to a soft brake pedal and one form of brake fade.
My preferred method of replacing brake fluid is to use a clean turkey baster to remove as much old fluid from the reservoir as possible. Refill it with fresh, clean fluid from a sealed bottle, then open the bleeder screws and let the fluid drip for a while from them. This is "gravity-bleeding". You might have to "irritate" the brake pedal by hand a little to get the flow started, but as the level in the reservoir drops, keep adding and end up with it at the same level as when you started. This method takes the longest so you might consider pedal-bleeding with a helper. Do just one wheel at a time until clear fluid comes out, then move on to the next wheel. Be sure to tell your helper to never push the brake pedal over halfway to the floor. As long as you don't let the reservoir run empty, no air will get trapped in the ABS hydraulic controller.
I mentioned that "clean" turkey baster as one tool. Regardless what you're doing with brake fluid, it is critical that you don't allow any contamination from a petroleum product such as engine oil, transmission fluid, power steering fluid, axle grease, or penetrating oil. Professionals even wash their hands with soap and water before handling parts that contact brake fluid to avoid contamination from fingerprint grease. I can go into a lot more detail if necessary, but for now, just one drop of a contaminate can result in a repair that costs more than a 2006 model is worth. Better to just be aware of this precaution.
Let me know if this helps, or if I should elaborate on anything.
Sunday, June 1st, 2025 AT 3:53 PM
