I put a new, not rebuilt, brake booster and (one holer) master cylinder on recently. The other day, I had to slam on the brakes pretty hard; the rearend came around on me and I damn near wrecked.
So, I took the car over to a friend's house to check it out; he's really good w/brakes. He checked my work, and says I did everything right - brake pedal rod adjustment, the brake light switch, etc and everything looks good.
He drove the car, slammed on the brakes a couple times and they didn't really lock up, but they're WAY too sensitive. He says the problem is in the booster. So before I see if the vendor will replace it, I wonder if the brake gurus on here have any other ideas?

Thanks a lot! :D :thumbsup:

ttt

How is the brake booster rod that goes into the master? Is that set too far out?

That was my first thought. The new booster came with 2 different length rods, and I used the same length rod as the old booster had (the longer one).
I had to adjust the bracket that goes on the pedal arm quite a bit for the new booster because the pedal was bound up with no travel at all, which I thought was odd since the same length booster rod was used.

Dave

Do you have a proportioning valve on this? Does this car have discs in the rear?

Is this booster for disc/disc, disc/drum, or drum/drum setup?

Just wondering, as these are different things to look at for causing lock-up of brakes.

Please let us know, as these are all areas to look.

Thanks
Bill

Dave
Do you have a proportioning valve on this? Does this car have discs in the rear?
Is this booster for disc/disc, disc/drum, or drum/drum setup?
Just wondering, as these are different things to look at for causing lock-up of brakes.
Please let us know, as these are all areas to look.
Thanks
Bill

Sorry Bill,

I should have made this clearer :clonk:; No prop valve, drum/drum.

Sounds like your "new" booster is not sized properly for your original drum brakes ( too much assist) ......adjusting the rod may help .......in hindsite you would have been better off rebuilding your original booster .is your new master cylinder the correct bore size for 66 PB ?? You pbly know this but when brake pedal / rod adjusted correctly the brake pedal is about halfway closer to the firewal than the clutch pedal

Sounds like your "new" booster is not sized properly for your original drum brakes ( too much assist) ......adjusting the rod may help .......in hindsite you would have been better off rebuilding your original booster .is your new master cylinder the correct bore size for 66 PB ?? You pbly know this but when brake pedal / rod adjusted correctly the brake pedal is about halfway closer to the firewal than the clutch pedal

It's the "correct" size booster - 9".
Car didn't come w/PB; I added PB some 20+ years ago; don't know about the MC bore size, I'll have to check that.
Car is an automatic, no clutch pedal.

Old M/C bore is 1", new M/C bore is 1 1/16". Or something close to that; the new bore appears to be slightly bigger.

Are you telling me that makes a difference? I'm still learning this stuff, so I sure don't know. :D

Thanks again!

Old M/C bore is 1", new M/C bore is 1 1/16".

Are you telling me that makes a difference? I'm still learning this stuff, so I sure don't know. :D

Thanks again!

Been a while since I rebuilt mine but If I recall my factory PB master cylinder is 7/8 so check out what you should have ...assume you dont have factory metallic brake option ...so maybe that why i have 7/8 but 1" or 7/8 are the two sizes for 66 drum cars and yes can make a diff

Been a while since I rebuilt mine but If I recall my factory PB master cylinder is 7/8 so check out what you should have ...assume you dont have factory metallic brake option ...so maybe that why i have 7/8 but 1" or 7/8 are the two sizes for 66 drum cars and yes can make a diff

I just checked my receipt from NAPA and the M/C I installed is listed as: "w/ Heavy Duty Brakes w/ Metallic Linings".

You're correct, I don't have the factory metallic brake option.
So, maybe this is the problem, eh? I really don't see what the big diff between the 2 M/Cs is, but what do I know? :D
This is beginning to annoy me.

Thanks!

.