I wanted to say thanks to Scotty for the shout-out advice he gave about overhauling the brakes on my 1979 Catalina a couple weeks ago, and thanks to Chuck Tobias, amongst a couple other users who've given me pointers over the last month dealing with this. I did my fourth round of brake bleeding this evening expecting the worst and the 3rd new master cylinder finally didn't leak. BrakeBest wheel cylinders for the car did not match the threading on the lines at all. New AC Delco cylinders fit, though not as cleanly as the original 1979 cylinders -old car OEM parts for GM are now made in China, not Dayton, Ohio.
This was my first complete overhaul of a braking system. I went through approximately 1 gallon of DOT 3 brake fluid, two brake lines, 3 master cylinders, four wheel cylinders and a good bit of frustration on this job before everything finally came back together, and the BRAKE warning light went off. The car's brake fluid was black throughout the system. I actually thought it was Coca-Cola a couple of times, but the hose in the bottle cap said otherwise. All the fluid is now brand new. A new set of P205/75 R15 white walls are all I need to get her on the road again.
Here's something I'm curious about. How do these old cars know there is a problem with the brakes so they illuminate the warning light? There is no level sensor on the fluid reservoir, like a more modern car.
Great-looking car, glad the brakes came together! The "quality" of even OEM parts these days is very frustrating. In many cases it's not much better even on newer vehicles.
As Scotty says the brake warning lights on cars of that vintage light up when pressure is lost, or there is a pressure differential between front and back hydraulic circuits. If you look under the hood you will probably find a junction block or proportioning/combination valve that the brake lines go into that has an electrical connection for a pressure switch.
So basically the brake warning light tells you what you already know when the system loses pressure, that the brakes aren't working properly. Kind of like an idiot light for engine temperature that lights up to tell you you're overheating while steam is coming out from under the hood. 🙂
Thanks! It was only $750. Haha. It needs some relatively minor body work and a paint job. Typical old car door-bottom rust. Only the driver's rear corner has come through, and just barely. The frame itself has minimal rust.
That makes sense about it being a pressure switch and differential pressure. I didn't fully seat the front right bleeder screw when I bled it, and air got in. I re-bled the line and the light finally went out. My girlfriend's dad drove the car down the gravel driveway and slammed on the brakes to test them. The wheels locked up and it slid like old cars do -no ABS. He said the brakes never grabbed that well before. It was his car that he just drove -it was a bargain repo yard find. When he parked it the last time, the brakes were so shot it would only drive in reverse.
Well they are pressure related so if you lose pressure that'll make the warning light come on as a pressure sensor
