Front Disc Brake Conversion Issues

[Hawaii]

Have a 73 that already had a booster and drums.
Conversion kit went on fine, BUT two issues now that I didn't have before:
#1) Brake pedal is still to the floor. Bled the front both with a partner and with an air compressor for an hour. Still spongy at best. Bled both front and back and still same result. Tried to bench bleed the front brake resivor of the master as well.
#2) After starting and applying brakes, my power steering unit began to whine and freak out out?!?! Acts like it has too much pressure. Never had this issue before? Checked fluids, etc.

Any ideas?

Mahalo!!!

 

[SHX669]

Did you replace the old MC with a new one for front disk ? It's not always necessary but sometimes .
You also need to remove the check valve for the front disk brakes {rear reservoir } if there is one in your MC.

 

[gr8scott]

Hey Hawaii,
Are the caliper bleed screws pointed up? The calipers can be mounted on the wrong sides such that the bleed screws are
pointed down. In that case, the caliper reservoirs will never fill up.
What kind of booster? Vacuum or hydroboost? Hydroboost works on hydraulic pressure from the power steering pump.
With a vacuum booster the two systems (brakes and steering) are not connected to each other and a problem with brakes
should not affect the steering.
Become a contributor so you can post pictures.
http://classicbroncos.com/photoupload.shtml

Edit: did you bench bleed the master?
[YOUTUBE]MjMfVzCxpR0[/YOUTUBE]

 

[thegreatjustino]

Did you grind the knuckles as you're supposed to?

 

[Hawaii]

Thanks all - the hydroboost and mc are new. Didn't remove the check valve though - I'll look that one up-thanks. Didn't pull it and do the bench bleed, tried to do it installed. Looks like the best way to do it is to pull it and do it in a vice? Calipers are installed correctly and fronded it down properly.

 

[jmangi62]

You know I've had this problem, and even had friends with the same thing, pedal goes to the floor after brake conversion, many things to check, so I don't have to repeat it. In my situation same thing, new everything pedal still went to the floor, no brakes, got pissed and moved to another project, which was removing rear chunk to install new gears and went to remove axle shafts and found the drivers side star adjuster laying in the bottom of the drum. WTF! Oh well, you never stop learning to check weird shit on these things. Jim

 

[DirtDonk]

A residual pressure check valve in the master cylinder will not cause the pedal to go to the floor. If anything, it will help keep a firmer pedal. You just don't want one for a drum brake in the disc brake section (rear reservoir) because the higher resistance could cause the pads to drag.

Many (most?) new masters do not even come with them anymore. Still, a good idea to check for them just in case.

Did you verify that the new master cylinder's piston face was compatible with the hydroboost's rod? If there is excessive clearance between the two then your pedal travel will be excessive too. Just a 1/4" extra gap there would add up to roughly an extra inch and a half of pedal travel.

And last, hopefully you did NOT push on the brake pedal while the master was unbolted from the booster. Hydroboost units don't take that too kindly and can fail easily.
Not sure if the symptoms are a flat pedal or not though, so check on that if you did push the pedal with things disconnected.

Paul

 

[hubdawg]

Had same problem from not grinding enough off and the caliper was not moving correctly. Ten minutes with a grinder and it worked like it should. Wish I would have done that first instead of bleeding the brakes 15 times!