Hello Coronet friends. I have a problem that occured on my 67' Coronet acouple days ago and im trying to figure out why. I will back up a few months ago when I was driving it 1 day, when my brake pedal got very firm. Instead of looking at anything specific I figured I might as well replace the brake booster and master cylinder since they both have a lifetime warranty and both were replaced about 8 yrs ago when I did the disk brake converion from 73-76 A-body parts. At that time I replaced the master cylinder which I got from the local auto parts store, which I told them was for a 75' Dart with front disk brakes and got a new brake booster for my car which is original for a 67' Coronet with power brakes. It worked pretty good for years, had to press pretty hard for it to stop since I do have a moderate cam but was ok. So like I said acopule months ago I replaced the master cylinder and brake booster and it was ok again. Now about 200 miles later I was driving it and the same problem occured where I have to stand on the brake for the car stop. Last night I started the car and was looking at all the possible problems such as vacuum leaks but none. Then this morning I pulled the vacuum plug off the booster and could here the air escape from the booster which obviously tells me that the booster held air pressure from the night before. I want to see what you guys think. Im really wondering if that would be the correct master cylinder since a Dart lighter then a Coronet? Any help would be appreciated, thanks.
The MC for the Dart is the same one as for the later model Coronets, and Diplomat body styles, so that's not it. It sounds like you have an issue with the booster.
67440Dodge Wrote:The MC for the Dart is the same one as for the later model Coronets, and Diplomat body styles, so that's not it. It sounds like you have an issue with the booster.
I agree...sort of... The hard pedal is a normally a symptom of a vacuum/booster problem; however, another possibility is the proportioning valve. If it shifts internally too far it can act this way also. If the car is stopping okay and the pedal is just hard, I would discount this and go with the vacuum/booster problem. If it is barely stopping, get it on jack stands and apply the brake and have someone try each wheel to see if you are getting proportional brake application.
Another issue that can cause a stiff pedal is a rubber brake line that has collapsed internally.
I was looking at this a min. ago and it does seem to be the booster again. I had the vacuum connected and then disconnected to the brake booster, while i was idling around and the the brake pedal feels the same, and car stops the same. Im going to step it up and go with a better booster, it figures the 1 part that is crap on the car has failed repeatedly, and I keep getting the same 1 because its lifetime warranty. I got the A-1 Cardone booster when mine originally failed shortly after I got the car back in 96' or 97'. This last time the booster failed, it was discontinued and Autozone had to send mine back to A-1 Cardone to rebuild it, then send it back to the store which took 2 weeks. Any suggestions on where I should get a new brake booster from, comparisons? Thanks for all your help.
Coronet1967 Wrote:I was looking at this a min. ago and it does seem to be the booster again. I had the vacuum connected and then disconnected to the brake booster, while i was idling around and the the brake pedal feels the same, and car stops the same. Im going to step it up and go with a better booster, it figures the 1 part that is crap on the car has failed repeatedly, and I keep getting the same 1 because its lifetime warranty. I got the A-1 Cardone booster when mine originally failed shortly after I got the car back in 96' or 97'. This last time the booster failed, it was discontinued and Autozone had to send mine back to A-1 Cardone to rebuild it, then send it back to the store which took 2 weeks. Any suggestions on where I should get a new brake booster from, comparisons? Thanks for all your help.
I have not had good luck with Cardone products. I always avoided using them at my shop. Napa seems to sell a Bendix Branded booster (it still may be Cardone so check with the counter sales staff); The part# NBB5473705 is a single diaphragm direct replacement to fit my 75 Coronet which should work great for your application, and for less than $85.00!!
Before you install a new booster, be sure that your master is not leaking from the bore and seeping brake fluid back into the booster.
Also, if your vehicle is running fuel rich, the vacuum fumes will contain high levels of fuel vapour that will prematurely ruin the booster seals. You can fix this by installing a small in-line charcoal filter.
Good luck!
"Before you install a new booster, be sure that your master is not leaking from the bore and seeping brake fluid back into the booster.
Also, if your vehicle is running fuel rich, the vacuum fumes will contain high levels of fuel vapour that will prematurely ruin the booster seals. You can fix this by installing a small in-line charcoal filter."
Good tip!!!!! FRATZOG
Ok, thanks alot guys. And actually the car does seem to be running rich. I have dialed down the carb. just right, timing is good, and it seems pulls consistantly thru the rpm range. When I got the 750 carb. from the previous owner, he told me that it had bigger jets. I had it rebuilt and the carb. shop that did it told me its a good carb. so I always figured that may be the reason it seems to run rich. I definately want to try and get a different carb. on it soon, If I slam the brake while driving the car practically shuts off. Where do I get the in-line charcoal filter?? Also I took off and looked at the back of the ms yesterday to check if it was leaking, and it isnt. Thanks again, Bill
Hey Fratzog, that booster is a A-1 Cardone. I called Autozone to see what they have for a 75' Coronet brake booster and they gave me a price of like $77 and said its made by Cardone. I asked for a part # and its as you said, without the NBB of course. Is the 75' Coronet brake booster diaphram any bigger then the 67' brake booster, maybe provide more air assist, it is a different part # then the 67' booster. Whats the difference? Thanks again