Team Chevelle banner
  • Hey everyone! Enter your ride HERE to be a part September's Ride of the Month Challenge!
1 - 5 of 5 Posts

·
Registered
Joined
·
15 Posts
Discussion Starter · #1 ·
i have a 72 chevelle with stock front discs with a big block. I have been chasing a hard brake pedal problem for a while now. i replaced the brake booster and it almost seemed worse. I had a little low vacuum (14”) so I put an electric pump with a auxiliary tank. I can pump up the vacum and come back 24 hours later and there’s still plenty of vacuum left in the system. I am getting 22” so I can’t blame low vacuum. I replaced the master and the front and rear flexible lines. I don’t know what to do. Could I have gotten a bad booster? Should I put my old 49 year old booster back on or should I just buy another new booster? Another question is-the replacement booster I got has the Delco Moraine stamp on it. The supposed original I have has no stamps or numbers on it. Did 1972 boosters have the Delco Moraine stamps on them?
 

·
Registered
Joined
·
857 Posts
Yes, they were gold cadmium plated with the logo on them. It sounds more like something isn't moving correctly. Pistons up front or wheel cylinders on the drums? Have you ever changed the brake fluid?
 

·
Registered
Joined
·
15 Posts
Discussion Starter · #4 ·
So the 1972 chevelle booster had the stamp on it? The booster that I thought was original on mine has no stamp. Maybe it was already replace. Back to the hard pedal and week brakes I read somewhere that with 100 lbs of pedal pressure you should get around 1100 psi at the caliper. I put a pressure gauge on a caliper and was only getting 600 lbs of pressure. I went to the master cyl and put the gauge in the front hole for the front brakes and got only 600lbs there. I replaced the master again. I still have the week brakes. I’m going to check the pressure readings at the new master cyl again. If im still only getting the 600lbs at the master I will have to consider trying another booster.. I’ve replace the fluid and blead the system. The only other thing I haven’t replaced Is the proportioning valve but I don’t see how that could cause low pressure at the master cyl .
 

·
Registered
Joined
·
1,592 Posts
Did you replace all of the brake lines? After almost 50 years, they could be full of rust and congealed brake fluid. Same for the flex lines at the calipers because they tend to collapse internally.

Rick

Sent from my SM-G965U using Tapatalk
 
1 - 5 of 5 Posts
Top