Sicklyscott

I'm looking for some help troubleshooting some brake issues on my '65 Cutlass. About 10 years ago, my father upgraded the front drums to a disc setup. For the most part it seems it was a company that packaged up a GM sourced conversion, meaning mostly OEM spec'd components. Once installed, it never quite had the stopping power it should have. When applying the brakes, initial grab is good but no matter how hard you slam on the brakes, you cannot get the wheels to lock up. It feels like incredible brake fade where at the end of your stop, you're really pressing on the brake pedal.

I have re-re-re-bled the brakes. We're good there. All pads, calipers and rear cylinders are in good working order. All brake hoses are new. Rear shoes are adjusted appropriately.

What I think is happening is the pushrod doesn't have enough travel and is therefore not applying enough pressure to the calipers. I've read a bit about the different rod lengths and am confused on what this car has. My initial thought is to climb into the footwell and try and adjust the brake pedal. There's a large threaded rod that attaches to it with a nut on the back. I'm assuming I can effectively raise the brake pedal which will give me more travel with the pushrod. Is that a correct assumption? Is there another adjustment I can make between the booster and the MC?

Without taking things apart, its hard for me to tell how it's all assembled.

-S

66luvr

I had a somewhat similar problem with a front disc conversion. After a few years I decided to try a simple, easy swap of the front pads. I took off the ones which came in the conversion kit from "The Right Stuff" supplier and put on a set of Wagner Thermo Quiet Ceramic pads and it made a HUGE difference. I still want to change the new booster which came with the swap for a dual diaphragm unit, The brakes are OK now but I want to change it anyway.

Sugar Bear

Single or tandem master? Jack it up then have someone apply the brakes and see if how each wheel operates.

Pushrod adjustment should adjust the pedal travel but not overall stopping power.

Good luck!!!

oldcutlass

Is the pedal going to the floor? How far down does the pedal go before you feel it actuating the brakes?

sysmg

Buy good quality brake pads and shoes. Some low cost pads may cause problems. There is a guy here called Mobileparts (search for it). He has NOS replacement pads and shoes for many cars and is reliable. I've bought from him with no problems. Actually I used to buy parts from his grandmother's parts place many years ago.

Schurkey

There are so many possibilities as to be mind-boggling. Is the pedal low? Rule-of-thumb: on a "normal" stop, the brake pedal when applied should be higher than the gas pedal at idle. Is the pedal squishy, or firm? Grab an infra-red themometer, go for a drive somewhere with no traffic, and stop the car firmly from at least 40mph. Verify the temperature of each brake--the fronts should be about equal temp, the rears should be about equal temp, and all four better be hot.

I'd be looking at the size of the pistons in the caliper vs. the size of the pistons in the master cylinder. The ratio is important.

Some master cylinders have a deep pushrod socket, some have a shallow socket. They match up to boosters that have longer or shorter pushrods. A mis-match causes problems.

Sicklyscott

In the end it was a combination between low vac from an aggressive cam and a bad brake booster. I did all the troubleshooting I could but couldn't get a vac pump going. I bought an electric unit and it wouldn't build enough vacuum for it to shut off. After I installed both, it's working well. This car hasn't stopped like this, ever.

Sugar Bear

Glad it is fixed. Thanks for posting the source of the problem and the solution.

Almost forgot...have any pictures?

Sicklyscott

Of the car? Certainly!

Sugar Bear

Very nice!

Yellowstatue

Yes, very nice. Do you have that many cars that you have to number the parking spots?

classicmuscle442

Nice looking '65, like the white top, is that a factory color red?