The 6 Best Automotive Seam Sealers

We spent 26 hours on research, videography, and editing, to review the top choices for this wiki. Most typically used in the restoration of classic cars, automotive seam sealants come in a small range of varieties. Used to cover both interior and exterior sheet metal overlaps in order to create an airtight finish, these products can either be applied via spraying or extruding, depending on your needs. Lovers of old autos in need of some TLC will find what they require here. When users buy our independently chosen editorial picks, we may earn commissions to support our work.

6. Transtar Ultra Flex

This Transtar Ultra Flex caulking tube is a urethane sealant of fair quality. Though it cannot be sanded down, its material composition makes it highly pliable, and makes it quite easy to smooth it out manually before it dries.

  • Good adhesive capacity
  • Lower than average cost
  • Somewhat stringy upon application

Model 4167
Weight 16 ounces
Rating 4.9 / 5.0

5. Carborundum EZ Repair

Many individuals in the restoration community swear by two-part epoxies, like Carborundum EZ Repair, particularly if they plan to drive their newly-refurbished automobile with a fair degree of frequency. This is specifically used on horizontal overlaps.

  • Ready for paint in half an hour
  • No shrinking or cracking
  • Needs specialized gun to apply

Brand Carborundum EZ Repair
Model pending
Weight pending
Rating 4.8 / 5.0

4. SEM Black

A reasonably-priced tube of SEM Black will dry hard and fast once applied, key for any effective product in this category. You may need an extra tool on hand to help spread it, but this is an excellent choice if you have something fit for that purpose.

  • Flows out easily
  • Holds shape well
  • Doesn’t come with applicator tip

Brand SEM
Model 29392
Weight 15.2 ounces
Rating 4.7 / 5.0

3. 3M Dynatron 550

A tube of 3M Dynatron 550 will service most exterior restoration needs very effectively. Its fast-skinning capacity is activated within minutes of application, allowing you to apply paint without a needlessly long waiting time.

  • Adheres to bare metal and paint
  • Designed to resist sagging
  • Can be sanded after drying

Brand 3M
Model 550
Weight 12.8 ounces
Rating 4.9 / 5.0

2. Evercoat 365 Brushable

A quart of Evercoat 365 Brushable is a good option for restorers who are aiming to closely replicate the original condition of their classic car. It’s also great for the small overlaps most often occurring in the interior of the chassis.

  • Highly versatile
  • Brushes on very smoothly
  • Less expensive than leading brand

Brand Evercoat
Model 365
Weight 2.8 pounds
Rating 4.6 / 5.0

1. 3M Flexiclear

A versatile option from arguably the biggest name in this market, 3M Flexiclear is equally applicable for use on interior and exterior joints. It’s nearly transparent once it dries, so it doesn’t need to be painted over when used for spot applications.

  • Remains flexible after curing
  • Adheres to a variety of surfaces
  • Doesn’t turn yellow in sun

Brand 3M
Model 08405
Weight 11.2 ounces
Rating 4.5 / 5.0