Three things cause the red light to turn on. The parking brake, the low brake fluid switch, and the "pressure-differential" switch. Not all vehicles have a low fluid level switch although in the last 15 - 20 years, most do.
Very often parking brake cables stretch or they can become sluggish and prevent the pedal from fully releasing. You would find that by simply pulling up on the pedal with your toes. On cars with a parking brake handle, you just push it down.
The pressure-differential switch just sits between the two brake hydraulic circuits and does nothing when everything is working properly. When anything causes pressure to build in one part when you press the brake pedal, but not in the other part, a valve moves and turns on that switch. Normally that happens when there's a leak but it can also occur after replacing the disc brake pads. To get technical for a minute, the pistons have to be pushed into the calipers to make room for the new, thicker pads. Those pistons come out about 3/8" over the life of the pads as they wear down. That is how all disc brakes self-adjust. Brake fluid fills in behind the pistons to take up the space and that's why the fluid level goes down in the reservoir, which might turn the red light on.
Once the pistons are pushed all the way into the calipers to make room for the new pads, and everything is installed and put back together, the last step is to press the brake pedal repeatedly to cause the pistons to come back out of the calipers until the pads contact the rotors. As soon as one does, pressure will start to build up like normal, but the other side might not have reached that point yet so no pressure will build up yet. That's where the light could turn on during a normal brake job.
There's a couple of points to understand related to your brakes. First of all, almost all front-wheel-drive vehicles use a "split-diagonal" hydraulic system. That means the left front and the right rear are on the same system and the right front and left rear are on their own system. That is done so if a leak occurs in either system, you will always have one front brake working. That also means the two front brakes are on different circuits, and that is why that pressure-differential switch can turn on when only working on the front OR the rear brakes. The second comment has to do with resetting that pressure-differential switch. On Chrysler and GM products that valve is spring-loaded to reset when you release the brake pedal, but they often stick. That happened once on my '88 Grand Caravan. A simple, good hard jolt to the pedal almost always frees it up so it will reset. That valve is not spring-loaded on Fords. Theirs have to be reset by opening the other circuit that didn't have a leak, then slowly pushing the brake pedal until the light goes off, then immediately closing whatever you opened. That requires two people and it can be REAL frustrating and time-consuming because that valve might stick, then pop free and go the other way and the light will still be on. I've have students spend two afternoons, with my assistance, trying to get a light to go out on an older Ford! I've never run into this on a Honda or heard people complain about it, but to see if that's the reason the light is on, you simply unplug the switch.
Before we get your pop involved, here's a couple of things you can try. First check the level of the brake fluid in the reservoir. Now that there are new pads on the front, the level should be close to the "max" level. If it's real low, add some new fluid from a sealed container. (By "sealed", I don't mean new; I mean that the cap wasn't left off any longer than necessary to pour it). Brake fluid will suck humidity out of the air so it's important to never let containers of it sit open. Also, whenever working with brake fluid, be extremely careful to never get any type of petroleum product in it such as engine oil, transmission fluid, or power steering fluid. Doing so will result in a couple thousand dollar repair bill; a lot more if you have anti-lock brakes. Professionals even wash their hands to avoid getting fingerprint oil mixed in with the fluid.
If the brake fluid level is okay, tap on the master cylinder a few times. If the warning light goes out, the float for the switch was sticking.
Another simple trick you can try is to turn on the ignition switch so the red warning light is on, leave the engine off, then watch the brightness of the light very closely as you push the parking brake pedal. If you see a barely perceptible increase in brightness when you do that, it's because the parking brake switch is turning on like it's supposed to. That means it is working properly and is not the reason for the light to stay on. That trick might not work on a vehicle as new as yours because that light might be turned on by a computer in response to any of those three switches. That trick was useful on older cars and trucks that didn't have computers involved.
One more comment that your father is likely aware of is to never push the brake pedal all the way to the floor on any vehicle more than about a year old. Crud and corrosion build up in the lower halves of the two bores the pistons ride in, in the master cylinder. Pushing the pedal to the floor, either during bleeding, running the pistons out of the calipers, or when surprised by a leak, runs the lip seals over that corrosion and can rip them. That will result in an internal leak, a slowly sinking brake pedal, the red warning light turning on, and the need to replace the master cylinder. If your brake pedal feels high and solid like normal, you do not have a damaged master cylinder.
If you haven't identified and corrected the problem by now, your father will need to unplug the three switches, one at a time, to see which one is not turning off, then we'll figure out how to proceed.
Monday, January 14th, 2013 AT 3:38 AM
