Thread: New power front disc brakes 67 GTO

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if you have a power booster on this car try backing the nuts off the master to the booster not off the fire wall . see if that makes them release . the rod or master could not match . you may have a bad master or one for front drums .if you take it right off and the front wheels move you know were you have the problem. you need a master for a power booster

Dave, how can I check the combination valve?
Pat, it is a MC for disc brakes. I bought a complete power front disc brake kit. It is actually the "corvette style" MC. I also know that I have clearance for the pin between the booster and the MC.
So, as far as I can find out, it is either:
1. Both front hoses bad.
2. Combo valve not centered. Now really sure how that is remedied.
3. MC damaged.

I believe the GM's of that era had a pin on the back side of the combination valve that if it were popped out, would mean the valve was not centered....Maybe some of the guys remember for sure, been years since I worked on one of them.....??????

Originally Posted by DennyW

All you have to do to center it if it is, is take the switch loose in the combo valve. The spring load inside will then center the pin.

Thanks Denny, couldn't remember for sure how they were on the old GM's... I left my memory someplace else and can't seem to locate it!!!!!!!!

Here is an interesting troubleshooting chart:

http://www.geocities.com/warlockpw/brakes.htm

mike in tucson

The combination valve is new and came with the kit. So it is not an original style.

Denny, I'll try opening the fitting at the MC. Sat morning early when it's not so hot!

Also, I never mentioned that I plumbed in a line lock between the MC and the combo valve on the front brake side. Maybe it could be the problem. I haven't wired it up so I assumed that fluid would just flow thru it. I also haven't hooked up the wire connection to the combo valve.

Remember, everything is new up front. New booster, MC, all lines, combo valve, line lock, calipers, hoses, rotors, and spindles.

BINGO?try bypassing the line lock. and see

Worked on it this morning rom 9:00am to 2:00pm. Here is the sad story.

Got the whole front end up on jack stands and removed the front tires.

1. Had the wife apply the brakes and release. I crack open the fitting on the output of the front brake side of the master cyl. The brakes would not release.
I know that the brakes will release if I crack open the bleed screw. Now I know that they will not by cracking open the MC fitting.
Therefore the problem must be between the MC fitting and the bleed screw.
2. I removed the Line Lock from the system and installed a female/female fitting to connect the input/output to/from the Line lock. Bleed the brakes and had the wife apply/release the brakes. They would not release. Must be either the hoses or the Combo valve.
3. Went to Autozone to get new hoses. They could not help without a specific automobile application.(My hoses are not original now). Went to Carquest, they look at the book and we find one that matches. I go home and install the new hoses. The flare fitting to the hose on the driver side will not seal. Run to the parts store, I make a new hard line and install. I get everything to stop leaking, bleed the brakes again. I apply the brakes and they will not release.

At this point it has been over 100 degrees in the garage for a few hours and I'm out of energy.
So I guess that it is something to do with the new combination valve.

My combo valve is like the one shown in the ebay auction below. Anyone familiar with these?

http://cgi.ebay.com/ebaymotors/GM-Pr...QQcmdZViewItem

yes i have used that type . you have the lines hook up right ?

Thanks all...
I went out this morning and bled the rear brakes. Now the brakes release perfectly. I did'nt understand about the spool centering. I thought that since the rear brakes were bled and I was just working on the front system, I could just bleed the fronts to get by. I've gone thru bleeding the brakes about 8 times altogether. The whole system we bled about 5 times and just the fronts 2-3. Well, I learned something else.
Thanks again to everyone, especially Denny on this one.