New master cylinder, brakes not effective

[josehf34]

I Changed my 74 Fury master cylinder with a new Cardone industries unit exactly equal to the old, bleed all the brake lines but now the brakes are not very effective

The brake pedal is hard, doesn't feel spongy like if there were air but l have to push the brake pedal to the metal to stop the car and even isn't possible to block the tires braking

What could be the problem ?

 

[Big_John]

Did you bleed the master cylinder before putting it on?

 

[josehf34]

Did you bleed the master cylinder before putting it on?

Mmm no, but if there's air in the master cylinder it wouldn't go out through the brake lines ?

 

[jstaples2]

I'd pull the mc and bench bleed it just to be sure.

 

[cantflip]

You also may have moved the pressure differential switch. After bench bleed and installation of the master... if no fluid seems to be coming from one circuit of the brakes (F or R) you may need to reset it... I don't recall a reset button on a Mopar, so you will have to open one bleeder on the side that is working and push with a fair amount of force to get it to recenter (make sure you use a secure hose on the bleeder or you will make a mess). You will have to judge if that's part of the problem... but the valve not only turns on the red brake light, it blocks (tries to) fluid flow out the damaged half of the system.

 

[josehf34]

You also may have moved the pressure differential switch. After bench bleed and installation of the master... if no fluid seems to be coming from one circuit of the brakes (F or R) you may need to reset it... I don't recall a reset button on a Mopar, so you will have to open one bleeder on the side that is working and push with a fair amount of force to get it to recenter (make sure you use a secure hose on the bleeder or you will make a mess). You will have to judge if that's part of the problem... but the valve not only turns on the red brake light, it blocks (tries to) fluid flow out the damaged half of the system.

I think this could be the problem. Just after change the master cylinder I removed the entire rear end to complete a pinion and gear change so I had to disconnect the rear brake main hose and I feel like the car is only braking with the front this brakes (is just a feeling, I'm not sure of this) and while bleeding the rear brakes it was a bit difficult to have fluid coming from the bleeder, i had to push the pedal like five times to have the fluid coming out while the front brakes with pushing one time the pedal was enough to see fluid coming out. How can I reset the valve or check how is set?

I'm going to bleed the master cylinder in a moment and see what happens

 

[boltupal]

If your pedal is hard it usually means the power booster is dead or not getting enough vacuum. If you replace the master cylinder , bleed it and each wheel it's the wheel cylinders and or the brake hoses. Don't forget about the hose that goes over the rearend.

 

[Big_John]

I have seen the rear flex hose fail internally and cause this same issue. Since you just had it off, I would suspect it might be the problem.