The brake light on my civic keeps coming on and off. It's garaged and I never use the emerg brake. A Honda shop told me that the brake line has a brake in it and they need to take the whole car a part to find it then fix it. They told me it would take about 5 hours to find and fix the problem. I held off for the moment and since I left there 4 days ago my brake light has not come on again. What is really going on?
Brake Light on 1991 Honda Civic
The brake warning light comes on when the brake fluid level in the brake fluid resiviour drops below a safe level. the brake master cylinder is attached to the brake pedal. Pressure is generated in the brake master cylinder proportional to the force you apply to the brake pedal. This pressure goes to each corner of the car via a metal brake line and goes out to the wheel through a flexible rubber brake hose. You don't say which metal line is in need of replacement but depending on location they can be difficult to replace. The brake hydraulic system should not "loose". It may drop a little as brake pads wear but if indeed a metal line is failing this could rupture and cause a sudden loss of a lot of brake fluid.
Has the brake fluid level gone down over the last couple of days? If I were working on the car I would inspect and insure the brake master cylinder rear seal is not the source of fluid leak. I would then use a pedal depressor to apply pressure to the brake pedal and leave the pressure applied for a period of time to see if that shows the area in which the brake fluid is leaking from, ( the brake light switch may need to be temporarily disconnected).
They state that they are not sure which brake line is leaking (front, rear, left right)and that is why they want to open up the whole car.
Have you been adding brake fluid at all? My guess is no, which is why you're holding off on the repair. When was your last brake job? The reason I ask is Honda, in their infinite wisdom, engineered the master cylinder reservoir to show a low fluid/ brake light when the pads were worn, before you started grinding metal parts. It starts intermittently, especially after a good hard brake. Just a quick flash here and there. As time goes on, it will stay on longer and longer, until it stays on for good until you refill the master or put on new pads. At least, that has been my experience. Hope that helps. Look at your pads.