Drum Brake Seizes

[cybspi]

I have a 94 K1500 pickup, 118K. 350v8, front disc, rear 10" drums, vacuum assist + RWAL, open rear diff.

 

First the truck started having a problem where at very low speeds (like in a parking lot), the rear right wheel would just lockup, very hard. I wasn't on the brake or gas, just idling. This was a very intermittent problem (once or twice in a month), so I took a look at the wheel that was locking up (the right rear), popped off the drum, and everything looked fine. Put it back together and problem dissapeared for another 200 miles.

 

Just this week, my truck has decided to bring back the problem, but now, it does the same thing at speed (50mph). Again, not on the brakes at all, the rear right just locksup.

 

So now, when I removed the drums this time, I saw some interesting things. The rear LEFT wheel's main return spring fell off the shoes and got all kinked up in the drum. Bear in mind this isn't the wheel that would lockup! The wheel cylinder was also shot on this side, it looks like they need the main return spring for the return action on the cylinder.

 

On the right side, there are a few more strange things... the front shoe is more worn on the bottom than the top. The rear shoe is fairly even, and (understandably) less worn. Also, when I pulled into my buddy's garage to take off the drums, the right drum was exceptionally hot, and the left was stone cold. I barely have to touch the brakes to get to his house, so I don't think this is normal....

 

I've removed all the hardware from both drums and inspected carefully. So here's a summary of what I've found:

 

LEFT

the main return spring was kinked up and off the shoes

the bottom return spring was weak

shoes were black, most likely from the brake fluid that was leaking from the dead wheel cylinder.

the drum shoes no scoring or heavy marks

 

RIGHT

the main return spring had a distinctly white spot, it could be from the ridiculous amount of heat from that brake.

the bottom return spring was very weak

the "nails" seem to be a little bent up.

 

I bought this truck used, fairly recently, so I dont know its history. It definately has relaitvely new brake lines running to the back, but thats it in terms of things that are different.

 

Can you think of a reasonable theory as to why this situation would cause the rear right wheel to lockup, occasionally at speed of 50MPH (fairly scary).

 

I'd like to have a solid reason for why all this happens before I spend 250$ to redo the rear brakes....

 

Thanks

 

-aaron

[pm26]

Here is a theory:

 

Somebody who had no idea what they were doing installed the brake shoe springs incorrectly. Also, the brake shoes are not the same size, the front shoe is different length from the rear shoe. Reversing the shoes may have caused some binding.

 

Leaky brake fluid mixing with the brake dust creates a paste that can cause severe drag when trapped between brake shoe and the drum, especially when it gets hot and expands.

 

When working on drum brakes, always disassemble one brake and at a time and finish one before starting the other. That way you have a reference when you ar enot sure which spring goes where.