3M Urethane Seam Sealer 08367 Black - High Solids, Flexible (Pack

In this review of the 3M Urethane Seam Sealer 08367, the bottom line is simple: this is a workhorse seam sealer for automotive and general paint prep where a permanently flexible, non-shrinking seal is required. It is aimed at technicians, body shops and experienced DIYers who need a thick, high-solids urethane that adheres to bare metal, primed metal and painted surfaces and cures by moisture for reliable performance in hot or humid conditions. The single biggest reason to buy is its combination of flexibility and durability that resists cracking under vibration and moisture.

Key Features

• Single component formula: Provides easy application with a standard caulking gun and bonds well to bare metal, primed metal and painted surfaces without mixing.
• Moisture curing property: Cures reliably in high heat and humidity environments so it performs consistently in shop conditions where moisture is present.
• Non-shrinking, non-cracking: Remains flexible after cure, reducing the chance of gaps reopening under vibration compared with solvent-based sealers.
• Quick paintability: Can be painted over in about 30-45 minutes, speeding up repair work and masking downtime between steps.
• Thick consistency: Fills large voids and can be smoothed to a featheredge or brushed for a neat finish on seams and joints.
• High solids, black color: Delivers good coverage and a durable, dark finish that blends where black seam seal is required.

Who It's For

This seam sealer is best for automotive body shops, collision repair technicians and experienced DIYers who need a durable, permanently flexible urethane to seal seams, gaps and joints. It is particularly useful where vibration and exposure to moisture are expected, and for projects that require filling larger voids with a product that sands and paints quickly.

Those who should look elsewhere include users who need an all-purpose household caulk for non-automotive surfaces or those who require a color-matching OEM sealer in a different shade; likewise, customers who need an included nozzle or specialty dispensing accessory should plan to provide their own application tip or tool.

Pros & Cons

Pros

• High solids, thick paste provides excellent fill for seams and gaps with good workability.
• Remains flexible after cure and resists cracking under vibration and moisture exposure.
• Adheres well to bare metal, primed metal and painted surfaces for versatile use.
• Quick paintability allows painting after 30-45 minutes to keep projects moving.

Cons

• Some users report mixed results with paint adhesion over the cured sealer, so spot testing paint compatibility is advisable.
• No application nozzle included in the pack, so an appropriate tip or gun may be needed separately.

Specifications

Brand	3M
Model	08367
Color	Black
Volume per cartridge	310 mL / 10.5 fl oz
Pack quantity	Pack of 2
Key properties	Single component, moisture curing, high solids
Performance	Permanently flexible, non-shrinking, non-cracking

Our Verdict

The 3M Urethane Seam Sealer 08367 is a solid choice for professionals and skilled DIYers who need a thick, high-solids urethane that cures to a flexible, durable seal. Its quick paintability and strong adhesion to metal and painted surfaces make it good value for repair work, though users should verify paint compatibility and provide their own nozzle for application.

Frequently Asked Questions

Can this sealer be painted shortly after application?
Yes; painting is typically possible after 30-45 minutes, though full cure time will be longer and testing with your paint system is recommended.

Will this adhere to bare metal and painted surfaces?
Yes; the single component formula is designed to adhere well to bare metal, primed metal and painted surfaces.

Is this sealer suitable for humid, high-heat environments?
Yes; its moisture curing property provides reliable performance in high heat and humidity conditions.