If you own a pickup truck with a tonneau cover, chances are you’ve dealt with leaks at some point. Tonneau covers are useful for protecting cargo in the bed of your truck, but leaks can let in water, dust, and dirt. One of the most common areas for tonneau cover leaks is between the tailgate gaskets. If you notice water pooling in this area or dripping down from the underside of the cover, you likely have a leak that needs to be addressed.
What Causes Leaking Between the Tailgate Gaskets?
There are a few potential causes for leaks between the tailgate gaskets:
Worn or Damaged Seals
The rubber seals that run along the sides and bottom of the tailgate can become worn down or damaged over time. Cracks or gaps in these seals will allow water to seep through. Hot summer temperatures can cause the rubber to dry out and deteriorate faster.
If the tonneau cover doesn’t sit flush with the top of the bed rails or tailgate, gaps can form where water can intrude. An improper fit is often the result of an aftermarket cover that wasn’t specifically designed for your truck bed.
Dirt, leaves, pine needles, and other debris can get lodged in the seals, preventing them from making a tight closure. The tiny gaps left by debris buildup turn into leak points when it rains.
Tonnueau covers secure to the bed with clamps or latches. If these have come loose over time, the cover can sag and separate from the tailgate seals. This allows water to drip through the gap.
How to Fix a Leaking Tonneau Cover
If you’ve noticed leaking between the tailgate gaskets, here are some tips for troubleshooting and fixing the problem:
Inspect and Replace Seals
Carefully examine the seals around the perimeter of the tailgate for signs of wear, dry rot, or damage. Look for cracks, tears, and sections that are coming loose from the frame. Any compromised areas will need to be replaced with new seals. You can purchase replacement gasket strips at auto parts stores.
Make sure to get the correct size for your make and model of tonneau cover. Remove the old seals completely and thoroughly clean the surface before applying the new ones using gasket adhesive.
Adjust the Latches
Try tightening any loose clamps or latches on the cover. They may just need some minor adjustments to pull the cover tighter against the tailgate seals. Don’t over-tighten, but make sure they are snug enough to create a flush seal.
Check the Alignment
Visually inspect the cover alignment. There should be an even gap between the cover and the bed rails on both sides. At the tailgate, the cover should sit flush or slightly overlap the seals.
If it looks uneven or sagging in areas, you may need to adjust the clamps positions. Loosen them first, then shift the cover until it sits squarely on the bed. Re-tighten the clamps and test for leaks.
Clean the Sealing Surfaces
Use a soft brush and mild soap and water to thoroughly clean the tops of the bed rails and the tailgate surface where the seals make contact. Check for any debris lodged in the seals and remove it. Rough surfaces and foreign material can impair an effective seal.
For additional leak protection, you can apply a bead of weatherstrip sealant along the top edges of the tailgate before closing the cover. The sealant fills in any small gaps and creates a watertight barrier. It can help compensate for slightly imperfect seals or alignments.
Add a Tailgate Seal
Some tonneau covers don’t have seals along the bottom edge of the tailgate. Adding a aftermarket tailgate seal kit can help close this vulnerable gap. The seal attaches to the tailgate edge and pushes up against the cover when closed. It prevents leaks along the underside of the tailgate/cover seam.
Upgrade to an OEM Cover
If you purchased an aftermarket cover, leaks are often due to a less than perfect fit. Upgrading to a cover designed specifically for your truck by the original manufacturer can improve the seal and alignment. Genuine OEM covers are molded to seamlessly integrate with your exact bed size and shape.
Testing Repairs for Leaks
Once you’ve addressed any leak points, be sure to test your work:
- Close the tailgate and tonneau cover and use a garden hose to spray the perimeter. Check for any drips of water entering the bed.
- Park outside during a heavy rain and inspect afterward for moisture inside the bed.
- Fill the bed with an inch or two of water. Close the tailgate and cover tightly. After 15-20 minutes, check under the cover for any wet spots indicating leaks.
You want the cover to be completely watertight after any repairs. Be prepared to reapply sealant, adjust the clamps or replace any seals that still show signs of leaking. With some diligent troubleshooting and proper sealing, you can stop those annoying tailgate leaks for good.
FAQs About Tonneau Cover Leaks
Here are answers to some common questions about solving leaks between the tailgate gaskets:
What is the best sealant to use for tonneau cover leaks?
Look for a flexible, rubberized sealant at your local auto parts store. The best tonneau cover sealants can adhere to metal, fiberglass, plastic, and wood surfaces. Make sure the sealant you choose is waterproof and UV/weather resistant.
Should I replace both tailgate side seals or just one leaking side?
It’s generally best to replace the seals in pairs to keep the sealing surface even on both sides. If one seal is worn out, the other side is likely deteriorating too. Replacing both maintains consistent coverage.
How do I get the old tailgate seals off before installing new ones?
Use a plastic pry tool or flat head screwdriver to gently pry up the seals, taking care not to scratch the tailgate surface. Adhesive remover or WD-40 can help loosen stuck-on seals. Avoid tearing the seals to keep removal clean.
What is the best way to attach new seals for optimal adhesion?
Thoroughly clean the area first. Apply a primer coat on the tailgate surface and let dry completely. Add the adhesive to the new seals, align correctly on the tailgate, then press down firmly for 60 seconds. Allow to cure for at least 2-4 hours before closing cover.
Should I lubricate the seals after installing new ones?
Yes. Use a silicone-based lubricant on the seals after installation. Avoid petroleum-based greases which could cause deterioration. Lube helps the seals glide smoothly when opening and closing the tailgate. Reapply every 2-3 months.
Will adjusting the latches help if the cover wasn’t installed properly?
It may help somewhat, but can’t fully compensate for an improper installation. Adjusting latches pulls the cover tighter but doesn’t correct alignment issues. For best results, the cover should be removed and re-installed correctly.
How can I tell if my cover needs to be realigned?
Inspect the perimeter gaps around the bed rails and tailgate. They should be even on both sides. Sit in the truck bed and check if the cover looks square or sagging on one side. Use a soft measuring tape to compare the gaps.
What is the benefit of upgrading to an OEM tonneau cover?
OEM covers are designed to precisely fit your truck make and model. The rails and seals integrate seamlessly for optimal coverage and weather protection. Aftermarket covers are generic fits and more prone to alignment issues and leaks.
How much does it cost to replace the seals on a tonneau cover?
Seal replacement kits can range from $20-$60. Additional supplies like adhesive, primer, remover and lubricant will add $15-$30. Taking the truck to a professional could cost $150-$300 for parts and labor. Doing it yourself saves significant money.
Preventing Future Leaks
To help keep your tonneau cover seals in top shape and avoid leaks:
- Inspect seals regularly for signs of cracking or drying. Replace soon after any issues are spotted.
- Lube the seals every few months with silicone spray to prevent sticking.
- Avoid overloading the truck bed which can warp the cover and impair sealing.
- Park in shade when possible to limit UV damage from sun exposure.
- Properly open/close the tailgate and cover to prevent bending the seals.
- Clean debris from the cover rails and seals after off-roading trips.
- Consider using a high quality OEM cover designed specifically for your truck.
By addressing any leaks promptly and performing preventive care, you can maximize the life of your tonneau cover seals. Just a little occasional maintenance will keep the bed of your truck protected from the elements for years to come.