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[aerodyn]

I'm not used forums before, but have extracted a great deal of good info. I'm in the process of reviving my '74 260Z for my son. I thought I was done with a total brake rebuild (new master, booster, rotors, calipers, shoes and wheel cylinders). I can't seem to get rid of a spongy pedal. Bled all fours twice. They were working ok prior to installing some reman'd calipers. The brake light now comes on. Any clues?

-C

[MikeW]

Welcome to the club. Did you bleed the master cylinder itself before the brakes?

[beandip]

Welcome to the club . You said that you have replaced the vac/booster. If by chance you pulled the rod that is in the booster on the engine side you may have dislodged the reaction disk . If this is the case you will have the result that the peddle will go almost to the floor . It is possible , although with a lot of luck , to get the disk back in place with out disassembling the booster. By just shaking it back in place . I was able to do it . Before you do anything with the booster ! Did you bench bleed the master before you installed it ? In any event , do bleed the master just in case . Just do it in place Then the wheel cylinders. Hopefully this is the trouble and not he booster . Gary

[Walter Moore]

How spongy is the brake pedal? If you pump the pedal several times does it eventually firm up?

I always have that trouble on cars when I bleed the brakes. The pedal just never feels right, but so long as the brakes actually work, and you can pump the pedal up to the point where it begins to resist before it hits the floor, it seems like the pedal always comes in within the first few stops.

I would still bleed the master cylinder one more time if you didn't bench bleed it before installation. On my 71 there are bleeders on the side of the master cylinder.

[aerodyn]

The first pump feels like ya aint gonna stop, next pump gets firmer and firmer. SInce my son is the usual driver, I'd rather not rely on "pumping them up". I didn't bench bleed the master since I'd just replaced the front calipers. I didn't expect the front brake reservoir to completely drain while I waited for the new calipers. The last time around I did try bleeding the master cylinder, no bubbles. Likewise the rears looked air free. I heard mention of a break-in on the front calipers, that perhaps the were retracting too much. After spending so much time, I'm thinking about taking it to Midas and say "fix it".

Any other ideas?

-C

[aerodyn]

Beandip - I had replaced the vac booster several months ago, along with the master and wheel cylinders. The fronts looked alright so I left them alone. The car had been setting idle for about 6 yrs and the brakes looked dry. As it turns out the front right inside caliper was frozen, which became obvious when the outside pad had wore through and trashed the rotor. All new rotors and reman calipers on front. Same vac-booster that seem to be working before. What is the symptom of a bad check valve on the booster?