Difficulty: Easy–Moderate | Time: 30–60 minutes | Tools Required: See below
What Is a Lock Pillar Quarter Window Seal?
The lock pillar seal (also called U-Jamb seal or door lock pillar seal) is the U-shaped rubber weatherstrip located where the rear quarter window meets the B-pillar or lock pillar of the door jamb.
This seal performs two critical functions:
- Seals the gap between the door and body when closed
- Fills the area under the quarter window vertical weatherstrip
Tools & Materials Needed
- 7-Piece Trim & Pry Tool Set (GL-30)
- 3M Black Weatherstrip Adhesive (GL-11)
- Screwdriver (Phillips and flathead)
- Nitrile Gloves (GL-10)
- Clean rags
- Rubbing alcohol or prep solvent
Step-by-Step Installation
Step 1: Remove the Old Seal
- Open the door fully to access the lock pillar area.
- If present, remove the quarter window filler piece (plastic or metal trim) first.
- Peel or pull the old U-jamb seal away from the pillar.
- Remove any retaining screws (typically 2–4 screws hold the seal in place on most GM vehicles).
Step 2: Clean the Mounting Surface
- Scrape off all old adhesive residue.
- Wipe the entire mounting area with rubbing alcohol.
- Let dry completely (5–10 minutes).
Important: Adhesive will not bond to dirty or contaminated surfaces. This step is critical for a leak-free installation.
Step 3: Dry-Fit the New Seal
- Hold the new U-jamb seal against the pillar without adhesive.
- Verify it sits correctly in the U-channel of the pillar.
- Check alignment with the quarter window vertical seal above it.
- Mark screw hole locations if needed.
Step 4: Apply Adhesive
- Apply 3M Black Weatherstrip Adhesive (GL-11) in a thin, continuous bead along the mounting channel.
- Wait 2–3 minutes for the adhesive to become tacky.
Step 5: Install the Seal
- Press the seal firmly into position, starting at the top.
- Work downward, ensuring the U-shape fully wraps the pillar metal.
- Install and tighten any retaining screws.
- Wipe away any excess adhesive immediately.
Step 6: Reinstall Trim
Replace the quarter window filler piece and any surrounding trim.
Testing Your Installation
- Close the door firmly.
- Inspect the seal from both inside and outside.
- The seal should compress evenly against the door without visible gaps.
- Perform a water test after 24 hours of adhesive cure time.
Troubleshooting
| Issue | Solution |
|---|---|
| Seal doesn't fit tightly | Verify correct part for your year/model |
| Door won't close properly | Allow break-in period; seal may need to compress |
| Seal pulls away from pillar | Re-apply adhesive after cleaning surface |
Jan 8, 2026