Faulty Master Cylinder?
1990 LeSabre, 80k miles, I think its all original parts, this is my sister-in-law'* car.
My brother and I replaced the pads and calipers about 2 months ago and at that time we also bled the entire system as the fluid was very dark. It braked just fine at the time. However, now it doesn't. With the motor running, the brake pedal will go down all the way to the floor with very little resistance and the car will not effectively brake. The fluid is also very dark and it seems like it has gotten low in the past couple months.
First I suspected bad wheel cylinders but upon inpsection I don't see any major leaks. One does appear to have some very slight weeping of fluid, but not nearly enough to justify the fluid loss that is showing.
Next, I was thinking the MC was bad. This car wasn't really treated well by previous owners and I'm thinking the fluid hadn't been changed in a long time and perhaps the old fluid and debris from the original rubber sections of brake lines have maybe damaged the mc.
Howver, I don't see any weeping of fluid where the MC meets the vacuum booster. So I really don't know where the fluid is going, other than the tiny leak at the rear wheel cylinder... but even that may just be water that got splashed up under the boot as no extra fluid comes out when the brakes are pressed while in the air.
Any thoughts? Right now I'm wanting to replace the MC and the rubber lines and possibly both wheel cylinders. Then I'm wanting to rent a vacuum bleeder from Autozone and bleed all the old nasty fluid out of the system. Does this sound like a reasonable plan of attack or am I missing anything?
I've replaced the MC, wheel cylinders, and lines on my LeSabre T Type before so it should at least be faster to do this time on another car.
RIPBC... Off to bigger and better things