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As far as a wheel cylinder, they will leak when bad. Now the brake drum. Did you fully turn down the self adjuster? Also, are the new brake shoes centered?
Here is a link that explains how in general drum brakes are repaired:
Here are the directions for removal and replacement. Take a look through them to see if you missed anything. Most often, the adjuster isn't turned in the entire way or the parking brake cable may note be fully seated. All attached pictures correlate with the directions.
2007 Chevy Truck Colorado 4WD L5-3.7L
Brake Shoe Replacement
Vehicle Brakes and Traction Control Drum Brake System Brake Shoe Service and Repair Removal and Replacement Brake Shoe Replacement
BRAKE SHOE REPLACEMENT
Brake Shoe Replacement
* J 21177-A Drum to Brake Shoe Clearance Gage
* J 38400 Brake Shoe Spanner & Spring Remover
Caution: Refer to Brake Dust Caution.
1. Raise the vehicle. Refer to Vehicle Lifting.
2. Remove the rear brake drum assembly.
3. Using denatured alcohol, clean the rear brake shoes.
Important: Before removing the brake return spring, adjust the brake shoes to the lowest position. This will reduce the tension on the retractor spring.
4. Remove the adjuster assembly.
5. Using a pair of channel locks, remove the retractor spring from the secondary brake shoe.
6. Remove the secondary brake shoe from the backing plate.
7. Using a pair of channel locks, remove the retractor spring from the primary brake shoe.
8. Remove the primary brake shoe from the backing plate.
9. Remove the return spring.
10. Using a pocket flat-blade screwdriver, press the lock tab for the park brake cable.
11. Hold the lock tab in place.
Important: Pushing forward on the park brake cable will unlock the cable from the retainer allowing the cable to be removed from the park brake lever.
12. Push the park brake cable forward.
Important: When removing the park brake cable from the lever, the park brake return spring will remain attached to the lever. DO NOT remove the return spring from the lever. If the return spring becomes separated from the lever, replace the rear brake shoes. The lever is part of the brake shoe assembly.
13. Remove the park brake cable from the lever.
1. Apply a small amount of high temperature silicone grease or equivalent to the contact areas between the rear brake shoes and the backing plate.
Important: When installing the park brake cable into the lever, a snap or clip should be felt or heard. This will indicate that the park brake cable is properly in seated in the lever.
2. Install the park brake cable in the lever.
Important: Ensure that the retractor spring is properly seated in the retaining bracket at the bottom of the backing plate.
3. Install the retractor spring on the backing plate.
4. Using a pair of channel locks, install the retractor spring in the primary brake shoe.
5. Install the secondary brake shoe on the backing plate.
Important: In the following service procedure, the retractor spring can be installed by the use of either the special tool called out or by the use or a pair of channel locks.
6. Using the J 38400 (1) or equivalent, install the retractor spring in the secondary brake shoe.
7. Install the park brake adjusting hardware.
8. Using the J 22364-01 (1), adjust the rear brake shoes.
9. Install the rear brake drum.
10. Lower the vehicle.
Let me know if this helps. Also, you asked about a bad wheel cylinder. I said they will leak when bad. They can also freeze up and not move. In that case, there will most likely be rust on the inside of the brake drum where the shoes would normally touch.
Feel free to ask questions if you have any.
Images (Click to enlarge)
Saturday, September 14th, 2019 AT 8:46 PM