83 Corolla Wagon Rear Breaks Not Releasing

toyota
corolla

#1

After doing the shoes, cylinders and bleeding: When I apply the breaks and take off again not all of the pressure to rears is released so very shortly the rear breaks start to bind up and wont depressurise until I turn off the car. No adjustments to the pushrod have been made, and very recently changed axle bearings on both side. Seems like theres something that should be obvious Im missing.


#2

You should have changed the brake springs. They’ve probably have lost much of their tension.


#3

Springs still have a lot of tension. Not original to 83. Seems to be some sort of hydrolic issue.


#4

Replace the flexible brake lines running to the rear brakes.

The inside of these hoses tends to swell and to deteriorate over the years. This swelling can trap fluid and not allow it to drain back to the master cylinder, thus maintaining some pressure on the wheel cylinders.

In your case, over a period of 26 years those hoses have seen a lot of service and are overdue for replacement–especially if the brake fluid was not faithfully changed every 3 years. While you are at it, replace the flexible brake lines running to the front brakes also in order to prevent future problems.


#5

By “very shortly the rear brakes start to bind up” do you mean they apply themselves while drving? If so, consider a bad booster.

The booster works by using the engine’s vacuum to pull a diaphragm and assist you. When the brakes are not applied the diaphragm should have vacuum applied to both sides, and when you wpply the brakes only the front side. If it’s defective it could have the pressure on only the front side and be in essence applying the brakes. Since the rear drums on your car are “self activating”, meaning that the friction of the shoe linings on the drum surfaces actually helps apply the brakes, this could be manifesting itself the way you describe. When you shut the car off, the vacuum on the diaphragm disappears and the brakes release.

If my first statement is incorrect, then ignore everything else. I’ll just blame my meds.


#6

All rubber/flexi lines are replaced with rigid.

Pressure gradually builds from each stop and go, within a few mins breaks are sqealing and grinding.


#7

This almost sounds like the self-adjuster is actuating every time you push the pedal. Have you gone back over that part of the installation?


#8

Check for a bad line or stuck proportioning valve. The P valve is actuated by a lever attached to the rear suspension arms(if you have one) This moderates the front vs rear brake effort to reduce nose dive during hard brakeing. The valve may not be releasing or be completely frozen leaving a very high pressure in the rear line until the fluid can push back through the line to the resevoir


#9

Well I doubt this is the problem but did you back off the adjustment before replacing the shoes? Did they fit tight when you put them on? If so they probably would heat up and get tighter.