OK. So I swapped the master cylinder to one for a late '60's full size RWD Buick. Bench bled, installed, system bled. Still locking up the front brakes. Pulled the wheels and found the driver's side was dragging pretty good. I backed off until the drum spun freely(like the passenger's side). Still locking up. I don't know if the rear brakes are locking up or not because the stopping action is rather "violent". I mean it almost puts me through the windshield @ 5 mph. Again, I got the booster and master cylinder as a unit and it's for a '78 Electra. But now at least I have the proper master cylinder.The only thing I can think of is the vacuum booster is too powerful? Any suggestions before I change the booster?
What style brakes??? Drum-Drum?? Disc/drum??? Disc/disc??? A '78 Electra would have been disc front, drum rear.
on my 72 chevelle the left front brake locks up so bad it jerks the steering wheel out of your hand. i cant find a solution either but with drum brakes im thinking since there isnt a proportioning valve so i think im going to have to adjust the left front looser than the rest to make it all even. im going to do this tomorrow ill post my results. but on yours it sounds the same that the front brakes are adjusted too tight Lonnie
50_Buick, is it late '60s or late'70s? A '68 could have drum/drum or disc/drum. A '78 would be certain to have disc/drum. If the brake shoes are dragging, it's possible the wheel cylinder is corroded and the pistons are sticking, or the hose is collapsed and not letting the fluid back. You've eliminated the master as the problem, by using two different ones (if I read this right). Did the car nosedive with the stock setup? Boosters can exhibit this problem. But when is the last time you worked on the wheel cylinders? If you haven't done the front brakes in awhile, all things being equal, the front shoes would not be dragging. This indicates, in descending order, 1 weak springs, 2 stuck pistons, 3 bad brake hose. 462 Chevelle, this sounds like 1 the right side caliper is seized 2 the brake hose is bad. Alternatively, there could be corrosion blocking the fluid in the steel tubes themselves.
Sorry for the redundancy in my post. The car is a '65 Wildcat chassis with drums front and rear. Since I'm totally re-doing the car, I was advised to change out the single M/C to a dual M/C. Unable to get a direct replacement, I figured a big car needs big brakes and got a booster/master cylinder for a late '70s full size car. This came with a disc/drum M/C. Under the advice I received from my initial post, I changed the M/C to one for a car with drums/drums(for a late '60s RWD full size car). Also, I did previously change the rubber brake lines. The new hardline for the front coming from the M/C goes to a "T" before branching to each wheel. The rear hardline is connected to the original hardline that runs to the rear of the car. There is no proportioning valve that I know of....
Install your original booster, if still good. Get a master cylinder for a '67-'68-'69 full size Buick with drums all around. Bring your booster to the auto parts store with you & match the pushrod length of your original booster to the replacement master. The rear line of the master will go directly to the rear brakes. Just get a connector to connect the lines together. The front line will go to the front brakes via the block that's already on the frame. Plug the line that originally went to the rear. "Curl"/"Coil" the brake lines you are going to make up. This is for vibration & flex so the lines don't break. Bleed the brakes & let us know.
Tom,I already have all the plumbing installed exactly as you recommend. I have a remanufactured drum/drum (late 60's)M/C installed on a remanufactured (late 70's) 11"booster. My original booster is smaller, maybe 8"... I tried to re-install the original booster but the push-rod actually extends out of the booster about 1 1/2"(and isn't removable). The new booster's push-rod is pretty much flush with the face of the booster.When I bought the drum/drum M/C at the parts store, the question of "Delco or Bendix?" came up. I wasn't sure, but the guy checked and found that both types of M/C was compatable with the same part number booster. So...I guess I'll get another booster, but this time I'll get one for a late 60's car.
That late 70's booster is made for disk/drum cars and is larger to apply more vacuum assist. That is going to be a bit of overkill on your car unless you swap in bigger brakes or swap to disk brakes on the front.
So hopefully a booster for a late 60's drum/drum will solve my issues... Can't really get much "bigger" brakes, and I don't want to swap to discs.
You'd be suprised how big drums can come. My rears are tucked inside 15" rims and there is less than an 1/8" clearence all the way around. By the way the correct booster for your car is sold by A1 Cardone under part number 5471324 They should be available through special order at Autozone and Advance. Rock auto also has some in stock. There is a hefty core charge though.
Thanks for the info!!! I'll get one ordered after work. I can start putting my doors on tonite while I wait for the booster.
You need the CORRECT master cylinder!!!! Bendix & Delco are NOT the same. One has a deep piston & one has a shallow piston, like what you already have. So the boosters CANNOT be compatible/the same/crossover. Someone, somehow is feeding you a little BS. Just my opinion.
Tom, you are so right! Just came home from the parts store and learned exactly that. I'm going to take a few pics of my M/C to show the guy behind the counter. I think I finally found someone who "gets it". I just wish he worked weekends....
