My 1988 Dodge Diplomat has a problem that is driving me crazy. The brake pedal creaks every time I apply the brakes. Some time fails to release completely. The linkage as far as I can tell is not sticking or binding. I have power assist. Car stops fine otherwise. Pedal does not sink to floor.
Any help would be greatly appreciated. None of this seems to be covered in any service manual.

Sprqay some WD40 on the brake linkage under the dash

I've lubricated the linkage. Took apart, cleaned, lithium grease. Took Master Cyl loose, lubricated rod. I'm getting too old for crawling under the dash, I'm about to park it. Last winter for some reason no power assist at all, next time I tried it worked fine except for noise, so I feel something is up with the booster.

The booster is probably leaking vacuum. Your complaint about the booster failing last year reinforces that.

The Imperial and D250 both made noise when I hit the pedal. Replacing the booster fixed the problem.

Thought I should follow up. I removed Power Booster, there is a binding in the movement and pushrod fails to return upon release. Sending out for a rebuild tomorrow.