2001-2007 GM/CHEVROLET DURAMAX 6.6L DORMAN 603-125 COOLANT FLUID RESERVOIR
Restore the cooling system integrity of your 2001–2007 GM/Chevrolet 6.6L Duramax diesel with the Dorman 603-125 Coolant Reservoir. This OE-style replacement is a direct-fit solution designed to replace cracked, leaking, or discolored factory expansion tanks.
Over time, factory coolant tanks on Duramax trucks can become brittle and prone to leaks due to constant exposure to heat cycles. The Dorman 603-125 tank is constructed from durable plastic, features molded-in level markings, and is designed to match the fit and function of the OEM unit. It includes the reservoir cap and overflow hose port, making it a hassle-free cooling system restoration part.
Features & Benefits:
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Fits 2001–2007 Silverado/Sierra 2500HD & 3500HD 6.6L Duramax LB7, LLY, LBZ
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Direct replacement for OEM coolant reservoir
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Prevents overheating from coolant loss due to leaks or cracks
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Transparent tank with level markings for easy fluid monitoring
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Reinforced plastic resists high heat and pressure
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Includes reservoir cap for a complete install
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Matches factory mounting points and hose routing
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Quick, hassle-free installation
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Ideal for routine maintenance or after cooling system repair
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Dorman quality backed by industry-trusted standards
Truck Compatibility / Applications:
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2001–2004 Chevrolet Silverado/GMC Sierra 2500HD & 3500HD 6.6L Duramax LB7
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2004.5–2005 Chevrolet Silverado/GMC Sierra 2500HD & 3500HD 6.6L Duramax LLY
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2006–2007 Chevrolet Silverado/GMC Sierra 2500HD & 3500HD 6.6L Duramax LBZ
The Dorman 603-125 Coolant Reservoir is a dependable OE-style replacement for Duramax trucks. It helps maintain proper cooling pressure and fluid levels, ensuring your engine stays cool even under heavy load or extreme conditions.
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✔️ Orders placed on weekends or holidays will be processed on the next business day.
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✔️ Shipping to PO Boxes, APO/FPO may be limited based on carrier restrictions.
California Proposition 65 Warning:
This product may expose you to chemicals including plastic compounds and engine coolant vapors, known to the State of California to cause cancer, birth defects, or other reproductive harm.
For more information, visit: www.P65Warnings.ca.gov
