Changed Master Cylinder and no longer have power brakes...

[Myasylum]

Yes, I have my share of issues...

I put in new brake lines, and master cylinder. Holds brake pressure, when I start the car, the pedal does sink (no not to the floor). However, it seems when I drive there is no power brakes. Brakes work, but it kind of rolls to stop rather than before where it would grab.

The plunger in the brake booster (which I assume is stock) had rust on it. I tried to clean it up, and the plunger did pull out of position (did not fall outside of the booster). It just slid back in place. Not sure if that had anything to do with it and using the stock Proportionary Valve.

Vacuum line is still attached.

This is a stock 1972 SSP with front disc and rear drums.

Any ideas?

Thanks!

 

[Davefinan]

Did you adjust the pin from the booster when you put on the new M C

 

[Myasylum]

You can do that?

Obviously not.

The pin just seems to slide out of position. Didn't really seem like something that could be adjusted.

 

[1 Wild R/T]

What was the bore size of the master cylinder you removed?
What was the bore size of the master cylinder you installed?

 

[Davefinan]

You can do that?

Obviously not.

The pin just seems to slide out of position. Didn't really seem like something that could be adjusted.

If there is no nut on the pin of the booster , then it is probably not an adjustable pin. You asked for ideas with no pictures so I did the best I could

 

[Myasylum]

Yea, it's the stock brake booster, so if those are nonadjustable, then I guess it isn't? I don't recall seeing a nut. Just that it slid out of place, and I slid it back in.
I watched a video on an old Corvette (different beast I know) and that one didn't have a nut and still turned to adjust. So IDK?

 

[1 Wild R/T]

Stock boosters are adjustable... But your symptoms don't match a misadjusted pushrod..

What was the bore size of the master cylinder you removed?
What was the bore size of the master cylinder you installed?

 

[Myasylum]

I would have to check to get that information. Everything is installed.

I just purchased one that was supposed to be stock equivalent.

 

[1 Wild R/T]

Well it don't take long to remove four nuts, leave the lines connected, roll it forward off the studs & get a measurement... Generic 71-74 master probably a 1 1/8" bore... get a measurement off the original....

 

[Don Frelier]

Was it bench bled?

 

[Davefinan]

Stock boosters are adjustable... But your symptoms don't match a misadjusted pushrod..

What was the bore size of the master cylinder you removed?
What was the bore size of the master cylinder you installed?

Actually. I had that symptom on two of my cars….tweaked the adjustable rod and what do you know , no more rolling stops that seem like they take forever .

 

[Myasylum]

Yes, it was bench bled. I will check the bore when I get home. Maybe I'll find a way to measure the depth of the hole before I stick it back in.

 

[kiwigtx]

Did you disturb the ballast resistor?

 

[Myasylum]

Now it's leaking from the proportional valve. Ugh! I had to retighten and have to re bleed the brakes. This is frustrating. I checked the pin with that tool and that is fine.
Checked the bore size. The new one is an 1 1/8". The old one is at a freinds house he measured 1" which doesn't seem right. I'll have to look closer over the weekend.

 

[1 Wild R/T]

If you look at the original parts books from the 70's it lists a 1-1/32 bore master cylinder for a 70-71 E body... A 72 B body is the same platform with the same brakes... So I expect it would use the same bore size... 1-1/8 seems to be what all the current master cylinders are listed as...

Pascal's Law hasn't changed so why has the M/C bore?

Find a M/C with a smaller bore... Or get your old one back and put a seal kit in it..

 

[Davefinan]

Did you disturb the ballast resistor?