I am at my wit's end with these brakes!

[KDMatt]

Alright guys, I know it's been a while since I've posted on here -- I usually just cruise the 'search' function for useful info , but I'm really scratching my head at my car right now.

I have absolutely no braking power in the thing, and I've replaced every part I can think of.

It's a completely stock setup, now with brand new:

wheel cylinders at the back (w/ new shoes)

master cylinder

brake calipers (with new pads)

I replaced all the rubber brake hoses a few years ago, and I put a new power brake booster on a number of years ago as well.

There are no visible leaks anywhere in the system, and it bleeds cleanly... what am I missing???

... and the whole thing is acting like there's no pressure whatsoever! The pedal sinks to the floor every time! All I hear is a faint groaning noise...

I even took it to the shop to have them bleed it (after doing it countless times myself), only to have the head mechanic shrug his shoulders and say "well, these old cars aren't meant to stop on a dime ya know" ... (to which I silently said "bull****.")

I'm going to go through the FSM again, but I haven't got a single clue what else could cause this behavior. You guys on these forums have rarely failed me in my nearly 8 years of ownership. Please help.

[olzed]

Brake booster/ master vac, is leaking

[KDMatt]

I've had a leaky brake booster/master vac before and it displayed the opposite symptoms I'm encountering, it was also coupled with a nasty "hissing" noise (the sound of escaping vacuum) every time I applied the brakes. Plus, when I had a leaky brake booster, the pedal was incredibly stiff, and this is not the case right now.

The pedal sinks to the floor regardless of the engine running or not running... it just happens to sink a little faster when the engine is running...

[beermanpete]

If the pedal is on the floor there is no hydraulic pressure. Even with a poor bleeding you should be able to get some pressure. I suspect your master cylinder is bad.

[KDMatt]

If the pedal is on the floor there is no hydraulic pressure. Even with a poor bleeding you should be able to get some pressure. I suspect your master cylinder is bad.

This was my instinct as well, so I replaced the master cylinder.

The symptoms did not change.

[SteveJ]

Please make sure you didn't install the brake calipers on the wrong sides. The bleed screws should be at the top of the caliper. Many people have made this mistake. It's relatively easy to do. You don't even realize it until you cannot get a firm pedal no matter how much you bleed.

[black gold man]

Have you done rear brake adjustment

[240260280z]

post 6 and post 7

ditto ditto

[madkaw]

I guess I'm having a hard time understanding when or how this happened? When did the pedal or brakes start acting like this? Has it always been like this?

Air in the line can be difficult to get out sometimes-even after you have bled a gallon through the lines. I had a mustang do this to me and it drove me nutz. It was air in the front line that somehow avoided being flushed out. Only after removing the front calipers and letting the pads come out past their normal travel and then shoving them back in(reverse bleeding) did I get the air out.

[djwarner]

When I bought my car the PO had replaced the vacuum source line to the power boost and had omitted the servo check valve resulting in no boost. Six months later the boost unit failed when its diaphragm ruptured. In both cases braking action was weak to nil but the pedal was stiffer than when the boost was working properly.

The fact that your pedal goes to the floor board indicates an inability to build a back pressure. This is only caused by a leak, air in the system, or a defective master cylinder.

Thinking as I write this, I had a problem with a 64 Renault Dauphine. First pressing the pedal, it would go to the floor. Repeated pumping would eventually build pressure. Releasing the brake for a few moments, and the next pedal press would go down to the floor again. That problem turned out to be a defective seal in the reservoir cap. I have no idea why, but replacing the seal fixed the problem.

When the pedal was pumped, you could see the fluid draw down. The seal was designed to allow air to enter as the fluid was used, and to seal that air in. With a defective seal, fluid would return to the reservoir once the brakes were released.

[Zedyone_kenobi]

I am willing to bet it is a rear brake adjustment out of whack.

When replacing rear wheel cylinders, it is easy to not adjust them properly and all the stroke in the brake pedal is used to move those rear wheel cylinders closer to the shoe.

Jack up the rear of the vehicle.

Take off the rear wheels

Put the car in neutral

rotate your brake drum until the rear wheel cylinder adjustment cog is in view. Adjust it until the brakes Just barely rub the drum

Repeat on the other side.

[conedodger]

Calipers are mounted on the wrong side with bleed screws at the bottom and or the rear shoes are adjusted way out...