* Worn or damaged return springs: These springs are crucial for pulling the brake shoes back away from the drum after braking. If they're broken, weak, or improperly installed, the shoes won't retract. This is the most likely culprit.
* Seized or corroded brake shoe pivots: The brake shoes pivot on pins or shafts. Rust, corrosion, or debris can seize these pivots, preventing free movement.
* Incorrectly adjusted or damaged self-adjuster: Many drum brakes have an automatic self-adjuster mechanism. If this is damaged or improperly adjusted, it might be preventing the shoes from returning. The adjuster might be completely stuck. Even if you're adjusting the star wheel (adjusting screw), the self-adjuster could still be the underlying problem.
* Brake shoes are binding on the drum: The new brake shoes might be slightly oversized or warped, causing them to rub against the drum and preventing retraction. A slightly out-of-round drum can also cause this.
* Contaminants in the mechanism: Dirt, grease, or brake fluid can interfere with the moving parts and prevent proper retraction.
* Incorrect installation: The brake shoes might be installed incorrectly, preventing them from returning properly. This could include incorrectly seated springs or levers.
* Broken or bent parts: Something else in the brake assembly, such as a lever or linkage, could be broken or bent and interfering with the retraction mechanism.
Troubleshooting Steps:
1. Inspect the return springs: Carefully examine the return springs for damage or breakage. Replace them if necessary.
2. Check the brake shoe pivots: Lubricate the pivots with a high-temperature brake lubricant (NOT general purpose grease). Try to move them freely by hand. If they're seized, you may need to carefully clean and free them up, or replace them.
3. Examine the self-adjuster (if applicable): Make sure it's operating correctly. Sometimes, manually operating the adjuster can free it up if it's slightly stuck. If it's damaged, replacement is necessary.
4. Check for binding: Rotate the drum by hand and feel for any resistance or rubbing. This helps identify if the shoes are binding.
5. Clean the brake assembly: Thoroughly clean all parts of the brake mechanism with brake cleaner to remove any dirt, grease, or brake fluid.
6. Reinstall brake shoes carefully: Ensure the shoes are correctly installed and that all springs and levers are properly positioned.
7. Inspect the drum: A damaged or warped drum can also cause problems.
If you've checked all these points and the problem persists, it's best to consult a qualified mechanic. Brake systems are critical for safety, and improper repair could have serious consequences.
