hydroboost brake pedal goes all down after replacing front calipers.

[bronco loco]

I had my HB set up for about five years and has worked without any problems.
My initial set up was 2002 hydroboost off a mustang cobra. 1976 bronco front disc brakes and rear drum brakes with a proportion valve, explorer pump with dual return right into the reservoir.

I replaced my rear axles during the winter and decided to convert my rear drum brakes to TBP rear disc brakes.
I also found out my front passenger caliper was not releasing, so i decided to replace the front center hose, left and right front hoses and calipers. the bleeder on the four calipers are facing up.

Now that I finished installing the brake set-up, my brake pedal goes all away down before any braking happens. The pedal is extremely soft.
I have bled the lines until the are no bubbles. The rear brakes work, but the front ones can still be rotated even while the brake is depress.

So I have 2 problems, a soft pedal and the front brakes not really stopping. There is some resistance on the front when the brakes are applied but not enough.
I am not sure if I allowed the brake reservoir to empty when I was bleeding the brakes, If so, will bench bleeding the master cylinder take care of this problem?.
I need to move the Bronco out of my driveway before Saturday because we are celebrating my youngest daughter's first communion. Any help will be really appreciated.

 

[bronco loco]

my mustang HB set up can be seen in my "garage"

 

[Rustytruck]

My guess, with the larger volume of the rear caliper bores you will need a larger bore master cylinder to make up the cylinder volume. This will get worse as the pads wear demanding even more fluid volume.

 

[bronco loco]

ok, I just pinch the from center hose and the brake pedal works as it should, once the pinch is released I'm back to soft pedal.

 

[Apogee]

It sounds to me like you have air in the front brake circuit, which would explain both the low pedal and the fact that the front brakes aren't actuating properly. If there's any chance the MC ran dry, then I would bench bleed the MC using the plugged port method...you could do this for just the front circuit and you could even do it on the firewall if you like. Reattach the front brake line and then rebleed the front circuit.

 

[2FAST]

It sounds to me like you have air in the front brake circuit, which would explain both the low pedal and the fact that the front brakes aren't actuating properly. If there's any chance the MC ran dry, then I would bench bleed the MC using the plugged port method...you could do this for just the front circuit and you could even do it on the firewall if you like. Reattach the front brake line and then rebleed the front circuit.

I agree. Sounds like air in the front brake system.

 

[bronco loco]

Thanks guys, I also think there may be some air trapped in the MC. How is the plugged port method done?.

 

[Apogee]

Thanks for the PM, however since others may have the same question, here's a link to Cardone's method for a plugged-port bleed.

There's nothing "new" about this method, except that some people are just suddenly becoming aware that there are options to the old recircultion method that so many have relied on forever. This method works better than the recirculation method and it conclusively tells you whether the MC is functional prior to installation, ruling out other potential issues down the road and making troubleshooting easier if there are issues.

 

[Justafordguy]

After you bench bleed the master, double and triple check your front calipers to make sure they are not on the wrong side. They will fit either side and look like the bleeder is at the top both ways but will only bleed completely if they are on the correct side.

 

[bronco loco]

Fix it, swap calipers and HD peel back to normal. Thanks for your help.

 

[Justafordguy]

Glad to hear it was an easy fix.