Sticky rear brakes ... yet another inquiry

#1
1971 3500S NADA dual system.

Brakes were completely redone about a year ago, cleaned, lubed, new rubber everywhere etc.

Symptom is after braking the car feels like the brakes are dragging--it moves from a stop with the accelerator, but slowly. After a few seconds things even out. Or, when stopped at a light, when the brakes are released, the car will not edge forward in an idle. I have come to find that usually (but not always) after a couple of good yanks on the emergency brake, the drag is released and the car will edge forward at idle and drives fine--hence the conclusion that the problem is in the rear unit.

So I put it up on the rack and fiddled with the rear unit. In the normal (unstuck) state drag from the (new) pads is a little tight, but not excessively so. Took out the outer pads, wiggled the calipers, the pivots are totally free. Checked the handbrake linkages, totally free and the levers restore to the stops. As mentioned, new seals and new hoses from a year ago.

This would suggest that the one or both of the tiny little pistons are dragging. I cleaned them but did not replace them when doing the brake job. Ugh.

Other suggestions???

Thanks gbvona
 

sdibbers

Well-Known Member
#2
Two things come to mind from my own experience of the same symptoms.

1] Check the air valve on the brake servo up front. I've had a slight leak there cause dragging before.
2]Other factor for me was the flex hose on the rear end. The hose looked fine, but the inside of the rubber had swollen over time causing the hose to act like a one way valve. It would open under pressure (you pressing on the foot brake) then close up, causing a slow return of brake fluid through the hose.
 
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