I have a '93 MPV (rear ABS) that is displaying some odd braking behavior. When I pump the brakes, the pedal travels slowly to the floor (it goes farther with each pump) until it bottoms out. Then the idiot light comes on. When I release the brakes, the braking returns to normal and the light goes out. There is plenty of fluid, though it is dirty and should be replaced. Does anyone have any ideas what these symptoms indicate?

Thanks.

Sounds like a bad master cylinder. If you just keep a steady pressure on it, will it slowly go to the floor? If so, rebuild/replace it. Don't worry about the brake fluid. Replacing it does nothing to help the aged, worn rubber parts and the fresh fluid does not contact the most vulnerable parts of the caliper. Better to follow up with rebuild/replace the wheel cylinders and calipers next lining change unless it has been done in the last few years. Once you have done that, all the old fluid is gone anyhow. The dangers of old fluid are greatly exaggerated.

When you reinstall the master cylinder, you must bleed it before connecting the brake lines. You must then bleed the calipers and wheel cylinders. Be very careful not to twist off the bleed screws. If they don't come with reasonable effort, pulling harder will just twist them off.

Labman
Thanks, I think that you are correct, nothing else fits. Yes, the brake pedal does travel all the way to the floor, albeit slowly. Thankfully there is a fair amount of room under the hood to work on things. I know what you mean by being gentle with the bleed screws - been there, done that, bought the new parts. :)

I will let you know how I make out - won't be getting at it until the weekend, though.

Thanks again, Andrew.