I have a 67 Cutlass that I have added power assist to my brakes and changed to front discs. The problem it is having is that the brake pedal doesn't seem to return as well as it should. If I pull it up it will stay but that's not the way it's supposed to work. The kit didn't have any instructions with it for adjusting the brake pedal, so how do I go about adjusting the brake pedal so it returns to the right spot every time and still have the correct feel and pedal travel? Thanks.

 

Power brakes will normally have a lower initial pedal than manual brakes. Also make sure you're in the right hole for power brakes on the pedal arm.

 

Is it vacuum power assist or hydroboost?

 

Vacuum

 

The rod and clevis that connects to the pedal is threaded on the top to adjust the height.

 

Right, I got that. But to continue that thought, how do I know when to stop adjusting? Do I just adjust it until the brake pedal returns far enough to touch the brake light switch? Like I said in the original post, if I pull the pedal up, it will stay there so not much room between adjusting far enough and adjusting too far. Is there a definite point to stop the adjusting or is it a "til it feels right" kinda thing?

 

You adjust it so the pedal is at it's upper most position against the stop, while being able to insert the clevis pin in and out with no real friction. The brake light switch is adjustable to compensate if a previous installer didn't do it correctly.

 

I'm pulling this thread back up because this is the same brake system having a similar issue. The brake pedal is adjusted so it is solid against the pedal stop and the brake light switch responds normally. But I was sitting in the car making Vroom Vroom noises.... Not really, but I had the engine running and noticed that when I raised the RPM the brake pedal was moving downward. The pedal is actually moving up and down due to engine RPM. I suspect this has something to do with engine vacuum, but does that sound like a bad booster? Would a diaphragm leak cause that? Engine vacuum is not massive, but it should be enough for power brakes. The brake booster vacuum is connected to the throttle body baseplate, would it make a difference if it were connected directly to a manifold port? Would a bad valve on the booster cause something like this? Should I adjust the pedal a bit higher so it has more pressure against the pedal-stop and override the fluctuations? I know how the system is supposed to work, but that doesn't mean I know how to troubleshoot something weird like this. Thanks in advance for responses.