Introduction
This manual provides instructions for the Dorman 904-5701 Heavy Duty Diesel Exhaust Fluid (DEF) Cap. This cap is designed as a direct replacement for the original DEF filler cap on specified vehicles, ensuring proper fit and function. It is engineered for durability and reliable performance, preventing leaks and maintaining the integrity of the DEF system.
Product Overview
The Dorman 904-5701 DEF cap is a crucial component for diesel vehicles that utilize Diesel Exhaust Fluid. It seals the DEF reservoir, protecting the fluid from contaminants and preventing evaporation. This cap is designed to match the original equipment in fit and function.

Image: Front view of the Dorman 904-5701 Diesel Exhaust Fluid Cap, showing its blue color and tether.
Vehicle Compatibility
This DEF filler cap is compatible with the following Dodge/Ram models. Verify fitment using your vehicle's make, model, and trim level to ensure proper application.
- Dodge Ram 2500: 2010
- Dodge Ram 3500: 2010
- Dodge Ram 4500: 2010
- Dodge Ram 5500: 2010
- Ram 2500: 2011, 2012
- Ram 3500: 2011, 2012
- Ram 4500: 2011, 2012
- Ram 5500: 2011, 2012
Setup and Installation
This section outlines the procedure for replacing your vehicle's Diesel Exhaust Fluid (DEF) cap.
- Preparation: Ensure the vehicle's engine is off and cool. Locate the DEF filler neck, typically near the fuel filler or under the hood.
- Remove Old Cap: Unscrew the existing DEF cap counter-clockwise until it is fully detached. If the cap has a tether, carefully disconnect it from the filler neck or vehicle body.
- Inspect Filler Neck: Examine the DEF filler neck for any debris, cracks, or damage. Clean the area if necessary to ensure a proper seal with the new cap.
- Install New Cap: Place the Dorman 904-5701 DEF cap onto the filler neck. Turn it clockwise until it clicks or tightens securely. Do not overtighten.
- Attach Tether (if applicable): If your new cap includes a tether, ensure it is properly attached to prevent loss.

Image: Top view of the Dorman 904-5701 Diesel Exhaust Fluid Cap, illustrating the tether mechanism.
Operation
The Dorman 904-5701 DEF cap operates by providing a sealed closure for the Diesel Exhaust Fluid reservoir.
- Sealing: When properly installed, the cap creates an airtight seal, preventing contaminants from entering the DEF system and minimizing fluid evaporation.
- Removal: To access the DEF reservoir, unscrew the cap counter-clockwise.
- Replacement: After refilling or inspecting the DEF, replace the cap by screwing it clockwise until it is snug. A secure seal is indicated by a slight click or firm resistance.

Image: Underside view of the Dorman 904-5701 Diesel Exhaust Fluid Cap, showing the internal sealing mechanism.
Maintenance
Regular inspection of the DEF cap can help ensure the longevity and proper function of your vehicle's DEF system.
- Visual Inspection: Periodically check the cap for any signs of wear, cracks, or damage, especially around the sealing gasket.
- Gasket Condition: Ensure the rubber gasket on the underside of the cap is intact and free from tears or hardening. A damaged gasket can lead to leaks or contamination.
- Cleaning: If the cap or filler neck becomes dirty, wipe them clean with a damp cloth. Avoid using harsh chemicals that could damage the plastic or rubber components.
- Tether Integrity: If equipped with a tether, check that it is securely attached and not frayed or broken.
Troubleshooting
This section addresses common issues related to the DEF cap.
| Issue | Possible Cause | Solution |
|---|---|---|
| DEF Cap Leaks | Cap not tightened sufficiently; Damaged or worn gasket; Cracked filler neck. | Ensure cap is securely tightened. Inspect and replace cap if gasket is damaged. Inspect filler neck for damage. |
| Cap Difficult to Remove/Install | Cross-threaded; Debris in threads; Overtightened. | Clean threads on cap and filler neck. Ensure cap is aligned correctly before tightening. Avoid overtightening. |
| Check Engine Light (DEF System Related) | Improperly sealed DEF cap leading to system pressure issues or contamination. | Verify cap is securely installed. Inspect cap and filler neck for damage. Consult a qualified mechanic if the issue persists. |
Product Specifications
- Model: 904-5701
- Brand: Dorman
- Material: Stainless Steel (Note: The visible cap is blue plastic, but product specifications list Stainless Steel, likely for internal components or tether)
- Color: Blue
- Dimensions (L x W x H): Approximately 4.1 x 4.2 x 4 inches
- Item Weight: Approximately 0.01 Ounces
- OEM Part Numbers: 572.3009; 52122496AA; 52122496AB; 52122496AC; 52122496AD
- UPC: 019495423416
Warranty Information
Dorman products are backed by a commitment to quality. For specific warranty details regarding the 904-5701 Diesel Exhaust Fluid Cap, please refer to the official Dorman warranty policy available on their website or contact Dorman customer support directly. Warranty terms may vary.
Support and Contact
For further assistance, technical support, or inquiries regarding the Dorman 904-5701 DEF Cap, please visit the official Dorman website or contact their customer service department.
Dorman Website: www.dormanproducts.com
Customer Service: Refer to the Dorman website for current contact methods (phone, email, chat).





