Need help with soft brakes

JacobM03

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Dec 26, 2023
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Location
Ontario
Vehicle Details
1992 Thunderbird Sport 5.0
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I swapped over from abs to conventional brake booster and 93 crown vic master cylinder and also redone my front brake lines with an adjustable proportionning valve for the rear brakes and I install everything dry as I didn’t know I had to bleed the master cylinder in advance.

Now I have bled my brakes many times, tried also running a lime from bleeder to inside master cylinder and pumped the brakes maybe 100 times per corner to make sure and I have tried the same with the bleeder on the master cylinder and yet my brakes are still soft (with the car off).

I have not tried the brakes out on the road yet as the car is still on blocks but the brakes do lock up when I have someone pushing them and try to spin the rotors.

What else could I possibly do or what could cause this? Ive bled through over a gallon of brake fluid already.
 
Pull the master back off. Carefully fill it with fluid. Reinstall it, after you are sure it's full. Refill the reservoir. open all 4 bleeders, with a tube into a bottle. let it run until the bottles are 3/4 full. keep the reservior full I use clear beer bottles. close the bleeders.Bleed the brakes, while pumping the master ,Rear pass, front drivers, rear drivers, front pass. Pedal should be stiff. If it's still soft, you have a problem with a caliper. Or you got a bad master.
 
Pull the master back off. Carefully fill it with fluid. Reinstall it, after you are sure it's full. Refill the reservoir. open all 4 bleeders, with a tube into a bottle. let it run until the bottles are 3/4 full. keep the reservior full I use clear beer bottles. close the bleeders.Bleed the brakes, while pumping the master ,Rear pass, front drivers, rear drivers, front pass. Pedal should be stiff. If it's still soft, you have a problem with a caliper. Or you got a bad master.
Tried all this, no difference pedal is still soft, brakes were working fine before I redid front brake lines and added the new master cylinder/brake booster. No clue where to go now.
 
When using the crown Vic master with the tbird booster, the pushrod in the booster is not quite long enough to reach the master. Luckily the solution is simple. Go buy a cheap 7mm 1/4” drive shallow socket and put it on the end of the pushrod coming out of the booster, then bolt the master back up. Re-bleed the brakes after that, and you’ll be good to go.
 
When using the crown Vic master with the tbird booster, the pushrod in the booster is not quite long enough to reach the master. Luckily the solution is simple. Go buy a cheap 7mm 1/4” drive shallow socket and put it on the end of the pushrod coming out of the booster, then bolt the master back up. Re-bleed the brakes after that, and you’ll be good to go.
How tall exactly should the shallow socket be ? Or should I mesure it up when I take off the master cylinder?
 
Honestly, as long as it is a shallow 1/4” drive, it should be fine. I have used craftsman, kobalt, and snap-on, and they all worked the same. I don’t recommend using a snap-on. I did that on the first conversion I did as a test, thinking if it worked I would replace it with a cheap one, however after hitting the brakes hard one time, it will be pressed on there and you will never get it off again, so I wasted a snap-on socket on that one.
 
Honestly, as long as it is a shallow 1/4” drive, it should be fine. I have used craftsman, kobalt, and snap-on, and they all worked the same. I don’t recommend using a snap-on. I did that on the first conversion I did as a test, thinking if it worked I would replace it with a cheap one, however after hitting the brakes hard one time, it will be pressed on there and you will never get it off again, so I wasted a snap-on socket on that one.
I read up JVO’s post on the seap to conventional brakes and never noticed anything mentionning that spacer, is it because its different for different models/years?
 
There's a page in the manual that references the proper length for n mn12 Why a panther master?
 
Figured it out, went back to JVO’s post and Mikey is correct, I just had never read that far down the post. I put a 7mm socket on the pushrod and backed it out to where in total with the socket it sat at 15/16th from the flange as others had wrote works and voila, my brakes are as hard as can be!
 

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