My cold brakes don’t work

Question:

I always read the Mechanic On Duty because it has such good questions and answers relevant to older cars. I have a 1954 Olds Super 88 post. It is restored and over the years I have completely restored the suspension and brakes.

My question relates to a brake issue I have had for some time. The car has power brakes and the power brake unit has been restored. I recently replaced the front shoes. The cylinders were redone a few years back and the drums were replaced then. Everything seems to be in order.

When the new shoes were replaced I made all the major adjustments to correctly align the shoes top and bottom, using the cam adjuster.

The issue is that when the brakes are cold there is a hard pedal and the car does not brake well. In fact, I cannot get the wheels to lock even with the most pressure I can place on the pedal. As the car is driven (say 10 miles) the brakes get better and better. At the end of that time they stop very well and I can lock the wheels relatively easily. This was the

same issue with the last brake work I had done about seven years ago. I have checked vacuum and it is good. All lines are tight to the power brake unit. Any ideas on what else I can check or is this normal with the newer linings?

Answer:

The problem you’re experiencing is definitely not normal unless you have metallic brake linings. Vintage metallic linings, such as those used on road racing and endurance racing cars in the 1950s, won’t do much to stop the car until they get sufficiently warmed up. I doubt that’s your problem, however, since it would be very difficult to even find vintage metallic brake linings if you wanted them, so I don’t think you somehow ended up with them on your Super 88.

Instead, the problem you have is most likely due to a defect with the brake’s power assist system. The most likely culprit is probably a bad check valve in the vacuum line from the engine to the power assist. This could cause it to take several minutes for sufficient vacuum to accumulate and actually assist in actuating the brakes.