Have you ever noticed water inside the cargo bed of your pickup truck after a rainstorm? Finding puddles or a soaked load is no fun. The water likely leaked in through gaps in your tonneau cover seams.
Tonneau covers keep your gear safe and dry. But over time, water can find its way past worn seals and openings. Knowing why this happens can help you fix the leaks.
Why Does My Tonneau Cover Leak?
There are a few common reasons water sneaks into tonneau cover seams:
Gaps Between the Rail and Cover
Tonneau covers attach to the top of your truck’s bed rails. Rubber seals help block water where the cover meets the rails. But these seals aren’t perfect.
Over time, small gaps can appear between the cover and rails. Wind-driven rain can push through small spaces. Water then drips down into the truck bed.
Worn or Damaged Seals
The seals around the edges of a tonneau cover take a beating. They get pushed, pulled, and twisted every time you open or close the cover.
Years of use can cause the seals to crack or split open. Damaged spots create gaps for water to seep through.
Old seals can also lose their flexibility. They become hardened and compressed. This stops them from making a tight seal against the rail.
Poor Bed Rail Design
Some truck models seem prone to tonneau cover leaks. That’s often due to the shape of the bed rails.
Rails with a flat top surface can allow water to puddle up. Driving rain can overwhelm drained holes in the rails. The water then leaks down into the truck bed.
Rails with grooves and channels on top can trap water too. Splashing water gets caught in recessed areas instead of running off the sides.
Loose Cover Fit
Tonneau covers should fit snugly against the bed rails all around. If the cover sits too high or pulls away, gaps appear.
Loose adjustment allows the cover to flutter in the wind. This widens gaps for water intrusion.
Distorted Cover Shape
Tonneau covers take a beating from cargo, weather, and use. Their shape can get warped over time.
Dents, buckles, and twists in the cover prevent it from sealing tightly. Gaps let water through, especially when driving in heavy rain.
How to Fix a Leaking Tonneau Cover
Don’t put up with a soggy cargo bed. Try these tips to stop rain from sneaking through your tonneau cover:
Plug Gaps with Sealers
You can temporarily plug small gaps around the cover’s edges. Waterproof tape or trim sealers block water from getting through.
Look for gaps where seals meet the front and sides of the bed rail. Also check the back rail if the cover doesn’t extend fully to the tailgate.
Apply sealers carefully to prevent adhesives from oozing out and making a mess. Check the patches after rains to see if they are helping.
Replace Worn Seals
Hard, cracked, or flattened seals can’t keep water out. New seals are needed to make a tight barrier.
Carefully remove the old seals from the cover’s edges. Clean the channel so the new seal attaches firmly.
Test the fit before permanently sticking the seals on. Make sure they press snugly against the rails all around.
Adjust the Cover
If your cover fits loosely, tighten it up to prevent flapping and gaps. Look for adjustment screws, straps, or tension controls.
Don’t over-tighten it though. Too much tension can warp the cover or prevent easy opening. Test different settings until the cover seals firmly but moves freely.
Bend Back into Shape
You may be able to reshape a slightly dented or warped cover. Carefully bend and flex it back into its proper form.
Work slowly to avoid cracking the material. Have a helper ease the cover as you apply pressure from below or above.
Serious damage requires professional repair or replacing the cover. But mild reshaping can extend the useful life.
Weatherstrip the Rail
If your truck’s bed rail design causes leaks, you can add weatherstripping to block water.
Self-adhesive foam strips stick to the top of the rails. The extra thickness tightens the seal between the cover and rail.
Measure carefully and cut the strips to fit the rails snugly front to back. Compress the foam when closing the cover for a tight seal.
Install New Drain Holes
Extra drain holes in the bed rails can help leaked water escape. This keeps it from pooling and seeping down into the truck bed.
Mark locations spaced evenly apart along the rails. Make sure they won’t interfere with cover mounts or hardware.
Use a drill to open new drain holes. File rough edges smooth so they don’t tear the cover seals.
Prevent Mildew and Rust
Once water gets past your tonneau cover seals, you need to deal with the consequences. Standing water can damage your truck bed and cargo.
Remove Wet Gear
As soon as possible after a leak, pull out any soaked items from beneath the tonneau. Water can quickly ruin cargo like fabric, cardboard, or electronics.
If you can’t unload gear right away, try to prop up the tonneau cover. Opening air flow will help items dry out faster. Just be sure to close it before more rain comes!
Use old towels or rags to sop up standing water in your truck bed after a leak. Look under the tonneau cover as well and dry any puddles.
Speed drying by blasting the area with a fan. Point it into gaps under the cover and propped-open back door.
Clean and Protect
Once all moisture is removed, coat the bare metal bed with a protectant. Spray-on truck bed liners help prevent rust from forming.
You can also mix up a cleaning solution of vinegar and water. Spray it onto affected areas to inhibit mildew growth.
Make sure to re-treat and re-coat regularly, especially after repeated leaks. Check under the tonneau cover too for hidden moisture.
When to Call a Pro
Some tonneau cover leaks you can fix yourself with careful work. But major damage may require an expert’s touch.
Rely on a professional truck bed cover installer if:
- The cover frame is bent or broken
- Securing rails are damaged or pulled loose
- Large sections of the cover are warped, cracked, or punctured
- Adjustment/tensioning systems are dysfunctional
- Advanced corrosion and mildew have taken hold
Shops that sell and install tonneau covers can handle repairs or full replacement. Ask around for one experienced with your truck and cover type.
With proper care and fixes when needed, a good tonneau cover should go leak-free for years. Keep an eye out for problems and address them promptly. Enjoy a dry truck bed for all your cargo hauling needs!