Brake Light Flashing but Brakes Work Great Diagnose a Flickering Brake Dash Light

Sue here. And have you ever had a person say, "Oh, there's a problem with my brakes, and I really think you should look at it," so you do them the favor, and you take the car for a ride? There's nothing wrong with these brakes, and they don't feel wrong. So, let's go for a road test and see what happens.

So, I'm driving along and everything feels good. Pedal's really high up there. It's firm, doesn't have, like, air in it. The way to test for air in the brakes, just in case if someone's did a brake job and bled them incorrectly, you come to a complete stop, keeping the foot on the brake pedal. Hold it firmly, at a red light or a stop sign or in a parking lot, and feel that brake pedal, and see if it stays there. It should not go down slowly. If it goes down slowly, you have air in the system. Not the case here. Everything seems fine. I don't know what this guy is talking about. Well, we'll just keep driving and go from there. Maybe there's a squeal. He said no noise. He just said, "There's a major problem with my brakes." Now, I sure hope it's not an intermittent master cylinder and this pedal drops to the floor, because then we're going to have a major problem.

I don't see anything wrong with these brakes. Let's just turn around. Whoa. There it is. The brake light's coming on and flickering. And my foot's off the brake pedal, and it goes out as I straighten the wheel out. I got a good idea what this problem is.

So, now we get the car in the shop, and I got a pretty good idea what the problem is. Brakes feel great, so I'm not going to bother lifting it on the lift. Let's pop the hood. So, the car we have here does have a sensor in the master cylinder. Let's check it to see if the fluid's low. Good way to check it without taking the cap off, because sometimes there's obstruction in there, there's a screen. You should just take a flashlight, put it close up there, and you can see the fluid way down there, and it should be up here. Take the cover off. Let's see if we can actually see inside there. Well, there is brake fluid because we have brakes. Oh, yeah. It's way down, way down in the bottom.

So now, the next thing to do is fill this up with the proper brake fluid that it calls for. This happens to be DOT 3 or 4. And then I'm gonna raise it up and check for leaks. If I don't find any leaks, which I don't think I'm gonna find because the brake pedal felt great, more than likely this is due to lack of maintenance or adding during, someone did a brake job and they didn't top it off. So, I'm lifting the car up and I'm going to check for any chance that this thing has a brake leak. So, I'm going to check flex hoses, calipers, wheel cylinders and the steel lines. But I'm going to show you where to start and look, and what to really look for and not to overlook.

So, we have a typical disc brake in the front. We have a caliper, and we have the flex hose, goes right into the steel line. And you can follow the steel line with a light, goes right up to the master. Check both sides. That was the driver's, now we're on the passenger side. I'm checking flex hose area, check for breaks, cracks, right into the steel line. Everything looks good. Follow that steel line. So, here we have the two brake lines, steel going to the rear. Bigger ones are fuel and return. So, here we have brake, small lines, some surface rust, but they're not soft at all. They're nice and steel, still looking good. And here is the factory splice, and the lines go right in here. That looks good. And, you're going to follow it on both sides, going around. Your vehicle may differ, but just take a general, looking for any flex hoses you can find, steel lines. This car looks pretty much in great shape, far as that goes.

Now, we have drum in the back, so that means we have wheel cylinders. Now, you have to take the drum, tire off, take the drum out to check these, or, because I know I don't have a leak, just doing a quick visual. I'm looking on the back side of this backing plate, looking on the drum, looking for any wetness coming out of here. And, here we can see where the wheel cylinder is mounted. So, we have the steel line going in, we have the bleeder screw and the two mounts. If this was leaking, more than likely you're going to find moisture around here or on the outside of this backing plate. It just spins out from the wheel turning and it'll fly right out. Seems dry, so I'm just going to move on.

So, this is what a typical single-piston caliper looks like. See this rubber seal on the outside? That's really just a dust seal, and that is embedded in a little bit, and inside this piston there's a ridge, and that's where the real seal is that you don't want to damage. Dust seal stops that inner seal from getting damaged. Let's take this apart real quick and I'll give you a show.

So, what I did was I added air to the back, where the brake flex hose goes in, acting like the fluid, and I pushed the piston completely out. Look at that. There is a caliper piston. That's exactly what it looks like, right? Wow, this thing is old, huh? Here's your dust seal, and right there is your seal that stops the fluid from traveling, right there. This is in good shape. It's not leaking. But, this gets overlooked a lot. People don't see it unless it's blown, but it could be seeping. And, if it's seeping, you're going to have low brake fluid and a traveling pedal. And what happens is that seal leaks, fluid goes right by, comes out the dust boot right here. So, you might find a little wetness like that. Don't bypass that. That means that that inner seal is no good. So, this caliper needs to be changed.

So, that wraps up one more diagnostic at the 1A Studio. Hopefully this video helped you out. If you're not a subscriber, please subscribe. Don't forget to ring that bell because it turns on all your notifications so you won't miss any future videos.