Bought a 1989 240SX - but brakes act strange!

[Rockhoundrob1]

I am new here...

We bought a 1989 240 SX (automatic trans) with 55,000 miles. Runs OK, but does need some work. The previous owner said the master cylinder was changed about 1-2 years ago.

When we drove it home, it seemed the brake pedal had to be pushed about 3 inches before the brakes would grab. Even then, if you push REAL hard, the brakes really won't come close to locking up. All other cars I have driven, you push the pedal 1 inch, then the car starts to slow down. Push hard and the car stops pretty fast.

We bled the brakes and no air. Also the brake fluid was a good color.

1) Is there a brake pedal adjustment? ( similar to the "freeplay" on a clutch pedal)? Why so much free play before the brakes start to slow down the car?

2) only other thing I can think of is 1 or 2 of the brake cylinders are frozen. But that would not explain why I have to push the brake pedal 3 inches before the brake engages and the car starts to slow down.

3) When you really push hard, it seems that is the limit and the pedal won't go down further and the car just slows down. On all other cars, push the brake pedal HARD, and the car almost screeches to a stop. But I can still feel there is more room to push the brake pedal. This car will just slow down, but nowhere as fast as I expect it to.

Any idea or suggestions?

[Rockhoundrob1]

After looking around on the internet... another possible issue is the brake booster? With it being 30 years old, is this another possibility?

[EFITTZY]

Check vac lines to the booster before replacing it

[Rockhoundrob1]

AH !! good idea! I'll check that first!

Still I would be shocked if the booster is good after 30 years! Rubber (diaphram) tends to break down after 20 years

[Rockhoundrob1]

I never would have thought this was the problem. There was air in the master cylinder. It was new when we bought it. What threw me off was how much it sunk and then hit something and was acting like it was braking manually. Whenever I drove a car that had air in the lines, the brake was very soft or spongy.

We decided to just separate the master cylinder from the booster and push on the brakes and no noise ( air hissing, etc...). So we disconnected the brake line from the master cylinder and pushed the fluid out and saw some bubbling. Flushed it out and bled the brakes again. Now it is MUCH better!

[slider2828]

Yeah it happens for a improperly installed bmc. Usually you have to bleed the cylinder itself and then the lines....

[Rockhoundrob1]

Well the brakes "work" fine now, but there is still that free play. My son found another post in this forum about adjusting the extension in the brake booster. Apparently there is an extender that pushes into the master cylinder and right now there is a gap. This gap is what happens when we first push the brakes. we push about 3 inches before the brakes engage.

I will have to look at it this weekend and see if that is the problem.

[Rockhoundrob1]

Well, I decided it was the master cylinder ( even though the previous owner said it is like 1 year old). I changed it out for a new one and now it sure is better. No free play ( sinking to the floor). No idea if the other guy had air in the master cylinder or the MC failed big time.

The only thing is I cannot LOCK the brakes. It slows down VERY fast, but tires don't squeal.

Is this normal? Brake pads are rather small compared to what I see on other cars I have worked on.