car_designer

A few years ago I put a 4-wheel disk brake kit on my 1972 Cutlass. I had a friend help with the installation who had installed this same kit on 3-4 Chevelles with no issues.

From almost the beginning the brakes do not always fully release when I take my foot off the brake pedal. Sometimes they will but other times I'll take my foot off the brake pedal and the car will not move. When that happens, if I stick my foot under the brake pedal and lift it slightly the car starts to roll freely.

My Cutlass was a factory power drum brake car.

So far what I have tried:
-Readjusted the rear calipers
-Replaced the master cylinder with a new one

The problem is still happening. A few times I have driven the car and it seemed like the problem didn't start right away but only after 10-20 minutes of driving once the car warmed up. Can't say that is always the case and I might just not have noticed every time since I have gotten used to automatically lifting the pedal with my foot.

On a recent drive the pedal went low and the brake warning light came on. After releasing and pressing the brake again the light went out but the pedal was still lower than I remember, but it has been 6 months since I last drove it.

Does anyone have any ideas?

MDchanic

Your brake pushrod is too long.

I had that problem once with a non-adjustable pushrod and fixed it by placing two washers on the studs fastening the master cylinder to the booster.

- Eric

car_designer

After a couple of years the issue finally seems to be solved by replacing the brake booster with a new one.

joe_padavano

So you paid for a new booster just to get the correct pushrod...

MDchanic

They say there's more than one way to skin a cat...

- Eric

joe_padavano

Yeah, I'm just a cheap bastid...

MDchanic

My washer technique worked for years on my Chevelle when I was a kid - and they were free because I found them at the bottom of the toolbox.

- Eric

car_designer

I had previously adjusted the pushrod and still had the problem.

One day I noticed after turning off the car I could hear the brakes slowly releasing. Hard to describe the sound exactly. Found a post on a non-Olds forum after a Google search where the guy was having the same issue and he tested without vacuum connected. I tested this first by just turning off the car in neutral on an incline and the brakes would always release. I then tried with the vacuum line disconnected and although very stiff as expected, the brakes always fully released.

Called the company I bought the kit from, told him what I tested and the guy said "sounds like a bad booster" and sent me a free replacement.

z11375ss

It absolutely was the booster. I had the same problem and replaced the "new" booster. All good. I could tell the brakes weren't releasing because on a hill the car would stay still. You could feel the brakes were engaged. (5 Speed). Weird thing though was that I replaced the booster and it was the wrong one. So I swapped back in the old booster. Just like you the pedal had a really bad feel to it. Not confident at all. It was going to almost the floor without engaging the brakes. I put the old booster on to drive the car while waiting for the new booster and somehow the problem cleared up. The pedal is awesome and the brakes release correctly. ????? When I saw your thread I thought it was mine from not long ago. LOL!