Wehrli WCFab Coolant Tank Billet Cap - Black Anodized

Precision Billet Aluminum That Replaces the Weak Factory Coolant Tank Cap on Duramax and Cummins Builds

The Wehrli WCF100543 is a billet aluminum replacement coolant tank cap finished in black anodize, designed for use on WCFab fabricated coolant tanks installed on 2001-2024 Duramax and 2004.5-2007 or 2010-2024 6.7L Cummins applications. Rated at 18 to 20 PSI, the WCF100543 matches the pressure rating of the OEM coolant system without the failure risk associated with plastic OEM-style caps that degrade under repetitive heat cycles. The WCF100543 is a direct replacement cap for any WCFab coolant tank and ships ready to install with no additional hardware required.

Key Features

• Billet aluminum construction for durability over repeated heat cycles
• Black anodized finish for corrosion resistance and clean under-hood appearance
• Rated 18 to 20 PSI to match WCFab coolant tank system pressure requirements
• Direct replacement for the WCFab fabricated coolant tank cap
• Compatible with 2001-2024 GM Duramax diesel applications
• Compatible with 2004.5-2007 and 2010-2024 Dodge/Ram 6.7L Cummins applications
• Drop-in replacement, no modification required
• Made in the USA by Wehrli Custom Fabrication

Specifications

What's Included

• 1 WCF100543 billet aluminum coolant tank cap, black anodized
• No additional hardware required

About Wehrli Custom Fabrication

Wehrli Custom Fabrication, known as WCFab, is a Woodridge, Illinois-based manufacturer specializing in diesel performance components for Duramax and Cummins trucks. WCFab produces coolant tanks, intake manifolds, intercooler piping, and accessories that are engineered, machined, and assembled in the USA. The WCF100543 cap is part of their coolant system accessory line and is designed to serve as a long-term replacement for the plastic OEM cap used on their fabricated tank kits.

Frequently Asked Questions

The WCF100543 is designed for use with WCFab fabricated coolant tanks on 2001-2024 GM trucks and SUVs equipped with the 6.6L Duramax diesel and 2004.5-2007 or 2010-2024 Ram trucks equipped with the 6.7L Cummins diesel. It is not intended as a direct-fit replacement for factory GM or Mopar plastic coolant reservoir caps.

No. The WCF100543 is specifically a replacement cap for WCFab fabricated coolant tanks. It does not replace the factory plastic coolant reservoir cap that came on the truck from the factory. You need a WCFab fabricated coolant tank already installed for this cap to apply.

The WCF100543 is rated at 18 to 20 PSI, which matches the operating pressure range of WCFab fabricated coolant tanks for Duramax and Cummins applications. Using an undersized pressure cap can allow coolant to vent prematurely and affect cooling system performance.

Plastic coolant caps degrade under repetitive heat and pressure cycling, especially in diesel applications that run higher cooling system pressures and temperatures. The WCF100543 uses billet aluminum construction that resists deformation, cracking, and seal failure over time. The black anodized finish also resists corrosion from coolant exposure.

Yes. Wehrli Custom Fabrication machines and anodizes the WCF100543 at their facility in Woodridge, Illinois.

The WCF100543 includes the integrated sealing element required to seat correctly on the WCFab coolant tank neck. No separate gasket purchase is required.

No. The WCF100543 is designed specifically for WCFab fabricated coolant tanks and uses the tank neck thread and seat profile Wehrli machines into their tanks. It is not compatible with the factory GM plastic coolant overflow reservoir.

The WCF100543 is the black anodized version. Wehrli also offers a clear anodized variant (WCF100472) for owners who prefer a silver or natural aluminum appearance. Both versions are functionally identical and share the same pressure rating and billet construction.

Installation Instructions

1. Allow the engine and cooling system to cool completely before removing any coolant cap.
2. Place a shop rag over the existing coolant tank cap and turn counterclockwise slowly to release any residual pressure before fully removing.
3. Remove the existing coolant tank cap from the WCFab fabricated tank neck.
4. Inspect the tank neck threads and sealing seat for debris or damage.
5. Thread the WCF100543 onto the tank neck by hand, clockwise, until snug.
6. Do not overtighten. The WCF100543 seats on the sealing surface and does not require tool tightening.
7. Start the engine and allow it to reach operating temperature. Inspect around the cap for any coolant seepage.

WARNING: This product can expose you to chemicals including lead and phthalates, which are known to the State of California to cause cancer and reproductive harm. For more information go to www.P65Warnings.ca.gov.