Datsun D21 Ute Rear Brakes rubbing (1 Viewer)

[Hilleye]

Having trouble with the rear brakes on my Datsun D21 ute/pickup.

Rear hubs are heating up to the point where the wheel rims are hot to touch after driving any significant distance (10km+). This started after mechanics replaced the brake drum pads, but this might just be coincidental though.

After this was initially noticed the handbrake was adjusted and it is definitely not contacting the drum (vehicle is able to be easily pushed back and forth with handbrake off), however the problem with the hubs heating up persisted.

Handbrake cable and rear brake line were replaced today to try and fix it, but the problem still persists.

Wheel bearings have also been checked as a possible cause, they're fine (although the grease will likely be degrading with all the heat going through it).

Next stop is the brake master cylinder. Theory is that it's possibly preventing back flow of fluid after releasing brake pedal, which is causing the brakes to rub slightly. It's only effecting the rear though so I have my doubts.

Anyone have any other suggestions?

 

[Hilleye]

After a drive yesterday I have some further symptoms, which might help diagnose the problem.

Top speed has been reduced by about 25+ km/h. Normally it's about 135 km/h and now the truck will only make about 110km/h.

Acceleration over 100km/h is non existent.

Engine RPM is 1000rpm higher to maintain 100km/h. Was 3000rpm, now 4000rpm.

Fuel economy has decreased.

Rear hubs are still heating up, but degree by which this is happening seems to be reducing (i.e. they aren't getting as hot now).

Too me this says that the engine doing additional work to overcome resistance that wasn't there before the brake shoes were changed. The rear brakes must still dragging somehow even though you can push the ute no problem at rest. I think potentially because the drums weren't machined when the new brake shoes were installed maybe the shoes are contacting some of the high points on the drum when moving.

Anyone have any other ideas how this might be happening or how to fix it?

 

[candp]

Remove the brake drums and loosely band the shoes with a tiedown strap. Have a assistant depress the the pedal while you look at the action. It could be a wheel cylinder, fatigued return springs, corroded master cylinder. Depending on the age of the brake system, it might be wise to replace all.