Why Test Your New Seals?
After installing new weatherstripping, it's important to verify that your seals are making proper contact and providing a watertight barrier. Testing confirms your installation is correct before you encounter rain or road splash that reveals a problem the hard way.
Below are three proven testing methods used by professional body shops and restorers.
Method 1: The Paper Test (Dollar Bill Test)
This is the quickest way to check seal compression and contact around your doors, trunk, or any hinged opening.
What You'll Need:
- A dollar bill or strip of paper (about 3-4 inches wide)
Steps:
- Open the door or trunk lid.
- Place the paper across the weatherstrip so part of it hangs outside when closed.
- Close the door normally—do not slam it.
- Grip the paper and try to pull it out.
- Proper Seal: You should feel firm, even resistance as you pull. The paper should drag—not slide freely.
- Weak Seal: If the paper slides out easily with no resistance, the seal is not compressing in that area.
- Repeat this test at multiple points around the entire perimeter (top, bottom, sides, corners).
💡 Pro Tip: Pay special attention to corners and the hinge side of doors. These are the most common weak spots.
Method 2: The Chalk Test (Tracing Powder Test)
This professional body shop method reveals exactly where your seal is (or isn't) making contact with the body.
What You'll Need:
- Soft chalk, children's sidewalk chalk, or spray-on tracing powder
- A clean rag
Steps:
- Clean the weatherstrip surface thoroughly.
- Apply a light, even coat of chalk or tracing powder to the entire sealing surface of the weatherstrip.
- Gently close the door or trunk—do not slam.
- Open the door and inspect the chalk pattern:
- Good Contact: Chalk transfers evenly onto the mating body surface all the way around.
- Poor Contact: Gaps in the chalk pattern indicate areas where the seal isn't touching the body.
- Mark any problem areas for adjustment.
⚠️ Important: If you have trouble getting chalk to transfer, apply a very light coat of wax to the body pinchweld first—the chalk will stick better.
Method 3: The Water Test
This is the definitive leak test and should be performed after the break-in period.
What You'll Need:
- Garden hose (remove the spray nozzle for a gentle, steady flow)
- A helper inside the vehicle
- Good lighting inside the car
- Towels for cleanup
Steps:
- Have a helper sit inside the vehicle with the doors and windows fully closed.
- Starting at the bottom of the door or window, direct a steady stream of water along the seal.
- Slowly work your way up, pausing at each section for 15-20 seconds.
- Your helper watches for drips or water intrusion from inside.
- If a leak is found, mark the exterior location so you can address it.
⚠️ Warning: Always start at the bottom and work up. Starting at the top can cause water to run down and mask the true leak source.
What If Your Test Reveals Problems?
| Test Result | Likely Cause | Solution |
|---|---|---|
| Paper slides out easily | Insufficient compression | Allow more break-in time; check door alignment |
| Chalk gaps in corners | Corner not seated properly | Re-seat and apply adhesive at corner joints |
| Chalk gaps along straight sections | Body pinchweld damage or seal misalignment | Adjust seal position; check for dents in channel |
| Water leak at one spot | Localized adhesive failure or gap | Apply 3M Black Weatherstrip Adhesive (GL-11) to problem area |
Allow for the Break-In Period
Important: New Metro SUPERsoft weatherstripping is intentionally oversized to create a tight seal. If your door feels stiff immediately after installation, this is normal.
Give your new seals 3-7 days of regular use to compress and conform to your door shape. Re-test after the break-in period before making any adjustments.
Tools That Make Testing Easier
For complete installation and testing confidence, our Complete Installation Kit (GLK-1) includes adhesive and application tools. Keep Nitrile Gloves (GL-10) handy for clean adhesive touch-ups.