nazen

This is for an '83 N/A, 109k miles.

So after replacing (within the past 6 months) the front rotors, all 4 calipers, and all the flexible brake lines, I went to bleed recently with my new Motive power bleeder.

Air and more air and more air coming through the lines. I bled everywhere. Unions at the master cylinder, unions over the rear suspension, calipers, etc.

I decided my master cylinder was bad, since I was seeing a small geyser of fluid in the reservoir when my friend pushed the brakes. Also, brake function was virtually nothing after all that bleeding.

Yesterday, I replaced the master cylinder. Vast improvement of pedal feel. Did the same bleeding strategy, in sequence, starting with the master cylinder. Pedal feels great when the car is not running. I would estimate only about an inch of travel before the brakes feel like they grab.

However, with the car running, the pedal feel is cut easily in half if not more. The brakes don't grab until what feels like halfway through the pedal travel. The car will stop, but it stops better if I pump the brakes then hold. That will get the pedal feeling as it does with the car off.

Also, I noticed that when I pump the brake pedal with the car idling, the idle will start to fall and bog within five or six pedal strokes.

I reason that this indicates a vacuum leak. What do you think? Is it close to the booster (the plastic valves) or possibly the booster itself?

Vacuum lines are original...working on replacing the 3mm ones along with the check valves at the booster. Clutch components are all replaced including master, slave, and torque tube bearings. Slave bled easily and well, and clutch pedal feels great.

Am I on the right track? Any diagnostics I can do?

Thanks,

--Shadetree

nazen

Well, problem solved. It was the old "short between the ears" gremlin.

I got to thinking, and remembered that when I ordered calipers, the driver's rear was shipped incorrectly, and belonged on the pass side, so that when installed on the driver's side, the bleeder screw was on the bottom...

You can probably guess. Took it off, pressurized the motive, flipped the caliper, bled the air that wouldn't come out before, and BANG!

Pedal is 100%, high and tight. Stops on a dime with nine cents to spare.

Next time I'll know...

xsbank

Well done! If you are unsure about vacuum leaks, you can get a kit to replace all the lines with silicone hose - quite a cheap solution and good for peace of mind. I also like the cool blue colour...