Line air? MC air? 2nd pump make INSTANT braking...

[Schrade]

The brake pedal in this '90 has just a little play - maybe 3/4" - 7/8" travel, before the brakes tighten up. A second stroke on the pedal, and it IMMEDIATELY tightens up.

Where's the air? In the line? Or in the master cylinder?

Or could the lines be collapsing? (car has 32K on the odo)

 

[Huskerman]

My 90 was doing the hard pedal thing and I thought it was the master cylinder or something. Come to find out it must of had the original fluid in it and at the time I changed it, it would have been 20 years old. I know the fluid was a very dark color. After doing that and checking everything else out, the brakes and pedal worked great after that......you might want to try that first......

 

[John Robinson]

Something to consider with brakes on a low mileage mostly stored vehicles. Long before I got back into Corvettes I was a motorcycle rider. In over 50 years of riding motorcycles I only had one new bike. What I rode were bikes I found that had gone unused for 5 or more years. Now to what that thought me. In almost all cases the brakes would not work . What I discovered was that the brake fluid would become gummy over time and form a hard coating on all the brake parts. Now as to how I fixed this problem. (I am not advocating that this is a good procedure for car brakes) I would start by flushing the old brake fluid out and replacing it with rubbing alcohol in the master cylinder. I would keep doing this until the fluid coming out of the brake bleeder on the caliper was mostly clear. Be prepared to see a lot of junk come out. At least in the days when I did this the alcohol dissolved the shellac from the brake fluid. Then I flushed the whole system with fresh brake fluid. This worked especially well on the lever actuated master cylinder. They were usually very tight when I tried to use the brake lever and when done the brake lever would work smoothly. All this to say that on a car you have a power assisted master cylinder. So it can be using enough force to make the brakes work. Which may explain why the peddle is doing what it is.

 

[vigman]

The other thing to consider.....

I assume you have bled the entire system ? Was the original fluid brown ?

The rubber take a form after sitting so long... and the back pressure in the system make the rubber .. move and you get a better seal on the 2nd stroke..
I just went through this on my G35 and wound up replacing the master...
Cold in the morning ( car off ) pedal traveled 1/3 of the way to the floor.. car on 2 pumps nice FIRM pedal 1.5 inch of play
Drove around a bit. pedal free play down to 3/4 inch... car off ( vac bled off ) 3/4 inch of play ( now hot under hood )

Next morning.. cold same deal

Replaced M/C, On the old one, no sweating off back of master ( 113K on original ) .. with the new master now perfect.. none of this pump up to be " better "

 

[Schrade]

No hard pedal there Marcus; had that on an '87 with a bad booster. Probably IS original fluid in need of changing...

Brake fluid is alcohol-based / compatible? Does it really solve deposits in the line?

MC seals are OEM too, I'm sure...