Gbody brake Guru's needed

[nawlins-tim]

I changed my brake booster the other day on my 1980 Wagon . I used a master cylinder that was on my old brake booster. Now, after bleeding the brakes and getting ready to take a test ride, I noticed the brake pedal is a half an inch away from the brake light switch. For some reason the Travel is different than before i started. Also the pedal preasure feels odd/not quite right. I had a friend helping with the bleeding therefore I was under the car and didn't get to feel the pedal till after we were done.
I know the pre 81 master and booster are different than the 81 and after. Im wondering if they gave me the wrong booster. I did some basic dimension measurement on the booster before the install and it seemed a match. My master cylinder is aluminum and from the pics on Rockauto, only the 81 and older are aluminum( is that correct?).
My car is at my house and I stay at a different location during the work week. How can I tell if I have the wrong booster? And is there more than one stud on my brake pedal are?
ANY IDEAS? PLEASE HELP.......

Ps: this is the Rockauto booster I used SKP SK5471271 https://www.rockauto.com/en/catalog...booster,1884#:~:text=New-,SKP SK5471271,-Info

 

[86 Salon]

All of those listed on RA show except heavy duty. Usually, wagons are heavy duty. It may or may not make a difference. Sometimes the HD are just a larger diameter and can be interchanged with the standard duty. There was no reason to open the hydraulic system to replace the booster, but if you did, start by bleeding the master cylinder and then bleed all four wheels, starting from LR, that RR, then RF and finally LF. make sure that there is no air in the system. Did you compare them side by side before installing? Was the push rod the same length from the rear to the pedal? Did you transfer, if necessary, the pushrod from the old booster that goes in the front side and pushes the MC? If you didn't, then the booster won't apply the MC fully and will require re-bleeding the brakes. Finally, if everything is correct, the brake light switch may have been pushed back in the retainer when you were removing the booster. If that's the case, just push it back forward until it touches the pedal arm. Good luck!

 

[bracketchev1221]

Does this use a threaded clevis to engage the brake pedal? You spin the clevis on to the rod out of the booster to set the pedal height? I haven't done one in years and can't remember if its the later ones that had it or my 70 chevelles and Nova that did.

 

[nawlins-tim]

All of those listed on RA show except heavy duty. Usually, wagons are heavy duty. It may or may not make a difference. Sometimes the HD are just a larger diameter and can be interchanged with the standard duty. There was no reason to open the hydraulic system to replace the booster, but if you did, start by bleeding the master cylinder and then bleed all four wheels, starting from LR, that RR, then RF and finally LF. make sure that there is no air in the system. Did you compare them side by side before installing? Was the push rod the same length from the rear to the pedal? Did you transfer, if necessary, the pushrod from the old booster that goes in the front side and pushes the MC? If you didn't, then the booster won't apply the MC fully and will require re-bleeding the brakes. Finally, if everything is correct, the brake light switch may have been pushed back in the retainer when you were removing the booster. If that's the case, just push it back forward until it touches the pedal arm. Good luck!

I did the correct bleeding procedure. And i did measure the New booster, which seemed to be identical to the one I removed. The new booster had a pushrod in place which seemed to be like the old booster.
And the problem im seeing is the pedal is not in the same position at rest as previously. It is depressed by about 1/2 inch. Thanks for the reply

 

[Ribbedroof]

The problem is that at this point nobody really knows what’s on any of these cars unless they bought it new. My 81 coupe had the wrong year master and booster on it which I discovered when I tried to replace one of them. Wound up replacing both. My 81 wagon has SAE studs in the front rotors and metric studs in the rear axle which after checking the code somebody had swapped in from a later (82+) model. Too many people think everything interchanges from year to year and in some cases you can get away with it, and others it’ll bite you down the road

 

[nawlins-tim]

The problem is that at this point nobody really knows what’s on any of these cars unless they bought it new. My 81 coupe had the wrong year master and booster on it which I discovered when I tried to replace one of them. Wound up replacing both. My 81 wagon has SAE studs in the front rotors and metric studs in the rear axle which after checking the code somebody had swapped in from a later (82+) model. Too many people think everything interchanges from year to year and in some cases you can get away with it, and others it’ll bite you down the road

I basically just changed the booster. Maybe Its the wrong one. Maybe its the correct booster but its defective. Ill keep at it. This comming weekend I will have to pull it back apart and take a CLOSE look.

 

[nawlins-tim]

Does this use a threaded clevis to engage the brake pedal? You spin the clevis on to the rod out of the booster to set the pedal height? I haven't done one in years and can't remember if its the later ones that had it or my 70 chevelles and Nova that did.

All the gbodys I ve seen the brake rod and booster pin are NON-adjustable.

 

[Hurricane77]

As long as the push rod on the old booster vs the new are the same, there's shouldn't be that big of a difference in pedal height.

I know you said you did the proper bleeding procedure, but people often overlook bleeding the master cylinder first.

 

[nawlins-tim]

As long as the push rod on the old booster vs the new are the same, there's shouldn't be that big of a difference in pedal height.

I know you said you did the proper bleeding procedure, but people often overlook bleeding the master cylinder first.

I did the master cylinder bleeding on the bench. Its got me pissed forvsure.
There IS a difference in 79-80 boosters and 81-86 boosters. They have different part numbers. Same goes for the master cylinders.
Got to dig in this weekend. Thanks

 

[pagrunt]

I did the master cylinder bleeding on the bench. Its got me pissed forvsure.
There IS a difference in 79-80 boosters and 81-86 boosters. They have different part numbers. Same goes for the master cylinders.
Got to dig in this weekend. Thanks

It'll be '78/'79 (vender depending) to '81 then '82 to '88 on the boosters. This is because of the change in the master cylinder to match the change with the calipers. The master cylinders will be iron for '81 & earlier, aluminum for '82 & newer.