So here it is, 89 formula under normal braking everything is fine for the first half of pedal travel and car stops ok but in an emergency stop situation or continue to push the pedal at about the half way mark it gets rock hard and does not stop. When I say it gets hard it's not a vacuum or booster hard it's like there's a brick behind the pedal. new booster,master,prop valve,hoses,rotors and pads. No one can figure it out! 1 pair of Buccaneers tickets to whoever can solve this nightmare!

 

Come on, Somebodies gotta know...

 

I have the exact same problem. No help really I'm afraid though. I was going to take the cover off above where the brake pedal is and make sure the isn't literaly something in the way of the pedal. I would love to know what causes this. The odd thing is even though the pedal stops moving any further pushing harder does seem to increase braking force, kind of like I've lost vacuum assitance halfway through the pedal travel.

 

Tried the calipers? Rear disc or drum?

 

4 wheel disc. I just orderd a moser 12 bolt with brakes so the rear calipers will be new soon but I have not replaced the front calipers.

 

this is a common problem that as far as I know, no-one has been able to figure out. I have the same issue with my car. I've converted to 1Le fronts, early model 4th gen (same as post '89) rear discs. New correct master cylinder, correct prop valve, replaced vacuum filter and vacuum booster (low mileage original, might still be bad?). new soft lines. pretty much....the only thing left is the hard lines, and they were flushed out.

same symptoms. brakes wells, but if you panic stop, you get a very hard pedal feel, and the car slows OK, not great. the funny thing is with the old discs, and rear iron discs, it still stopped about the same, which prompted the whole changeover in the first place.

my brother's regal with ls1 discs up front and drums out back will put you through the windshield, and he didn't even have to change the master or prop valve.

frustrating......