{"title":"2003-2004 5.9L Cummins Engine Internals","description":"","products":[{"product_id":"03-05-ram-25003500-cummins-03-05-to-2006-valve-cover-conversion-harness","title":"03-05 RAM 2500\/3500 CUMMINS (03-05 TO 2006+) VALVE COVER CONVERSION HARNESS","description":"\u003ch2\u003eValve Cover Conversion Harness — 2003–2005 RAM 2500\/3500 Cummins (Early to 2006+ Style)\u003c\/h2\u003e\u003cp\u003eUpgrading your 2003–2005 5.9L Cummins with a 2006+ style valve cover? The factory wiring harness connector changed between generations — making a direct swap impossible without this conversion harness. The Fleece Valve Cover Conversion Harness bridges the gap between your early 2003–2005 engine harness and the updated 2006+ valve cover, allowing a clean, plug-and-play installation without cutting or splicing factory wiring.\u003c\/p\u003e\u003ch3\u003eKey Features\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePlug-and-Play Conversion\u003c\/strong\u003e — Connects your 2003–2005 engine harness to a 2006+ style valve cover without cutting or modifying factory wiring\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEnables 2006+ Valve Cover Upgrade\u003c\/strong\u003e — Required adapter for installing a late-style valve cover on early 5.9L Cummins applications\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eClean, Professional Installation\u003c\/strong\u003e — Maintains factory wiring integrity for a reliable, long-term result\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDirect Fitment\u003c\/strong\u003e — Designed specifically for 2003–2005 RAM 2500\/3500 5.9L Cummins applications\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFleece Performance Engineering\u003c\/strong\u003e — Trusted quality from a proven diesel performance brand\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFitment\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e2003–2005 RAM 2500 \u0026amp; 3500\u003c\/li\u003e\n\u003cli\u003e5.9L Cummins Diesel\u003c\/li\u003e\n\u003cli\u003e\u003cem\u003eFor use when installing a 2006+ style valve cover on an early 5.9L Cummins\u003c\/em\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003eSKU: FPE-HAR-CUMM-VC-ADPT-EARLY | Vendor: Fleece\u003c\/p\u003e","brand":"Fleece","offers":[{"title":"Default Title","offer_id":54611804586276,"sku":"FPE-HAR-CUMM-VC-ADPT-EARLY","price":139.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0975\/7202\/8708\/files\/fpe-har-cumm-vc-adpt-early.jpg?v=1781302542"},{"product_id":"03-07-cummins-59l-oe-replacement-head-gasket-thick","title":"03-07 CUMMINS 5.9L OE REPLACEMENT HEAD GASKET - THICK","description":"\u003ch2\u003eOE Replacement Head Gasket (Thick) — 2003–2007 Cummins 5.9L\u003c\/h2\u003e\u003cp\u003eWhen it's time to rebuild or refresh your 2003–2007 5.9L Cummins, don't cut corners on the head gasket. This OE-replacement thick head gasket is engineered to provide a reliable, long-lasting seal between the cylinder head and block — restoring proper compression, preventing coolant and oil intrusion, and giving your Cummins the foundation it needs for years of dependable service.\u003c\/p\u003e\u003ch3\u003eKey Features\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eOE Replacement Design\u003c\/strong\u003e — Matches factory specifications for a proper, reliable seal on the 2003–2007 5.9L Cummins\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThick Gasket\u003c\/strong\u003e — Thick variant for applications requiring additional head gasket thickness, such as resurfaced or milled cylinder heads\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePrevents Coolant \u0026amp; Oil Intrusion\u003c\/strong\u003e — Seals the combustion chamber to prevent coolant and oil from entering cylinders\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRestores Compression\u003c\/strong\u003e — Ensures proper cylinder pressure for reliable starting, power, and fuel efficiency\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eQuality Construction\u003c\/strong\u003e — Built to withstand the high cylinder pressures and temperatures of the 5.9L Cummins\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFitment\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e2003–2007 Dodge RAM 2500 \u0026amp; 3500\u003c\/li\u003e\n\u003cli\u003e5.9L Cummins Diesel\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003eSKU: FPE-CUMM-HG-5.9 | Vendor: XDP\u003c\/p\u003e","brand":"XDP","offers":[{"title":"Default Title","offer_id":54611805012260,"sku":"FPE-CUMM-HG-5.9","price":159.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0975\/7202\/8708\/files\/fpe-cumm-hg-5.9.jpg?v=1781301246"},{"product_id":"03-18-ram-25003500-cummins-coolant-bypass-service-kit","title":"03-18 RAM 2500\/3500 CUMMINS COOLANT BYPASS SERVICE KIT","description":"\u003ch2\u003eCoolant Bypass Service Kit — 2003–2018 RAM 2500\/3500 Cummins 5.9L\/6.7L\u003c\/h2\u003e\u003cp\u003eKeep your Cummins coolant bypass system properly maintained with this complete service kit. Designed for 2003–2018 RAM 2500\/3500 trucks equipped with a coolant bypass, this kit includes the replacement hardware and seals needed to service the bypass system — ensuring leak-free operation and long-term cooling system reliability.\u003c\/p\u003e\u003ch3\u003eKey Features\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eComplete Service Kit\u003c\/strong\u003e — Includes all necessary hardware, seals, and fittings to properly service the Cummins coolant bypass system\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePrevents Coolant Leaks\u003c\/strong\u003e — Replaces worn or deteriorated seals and fittings that can cause coolant loss over time\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMaintains Cooling System Integrity\u003c\/strong\u003e — Ensures the bypass system continues to function properly after installation or routine maintenance\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBroad Fitment Range\u003c\/strong\u003e — Compatible with 2003–2018 RAM 2500\/3500 5.9L and 6.7L Cummins applications\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEasy Maintenance\u003c\/strong\u003e — Everything needed in one kit for a straightforward service job\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFitment\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e2003–2018 RAM 2500 \u0026amp; 3500\u003c\/li\u003e\n\u003cli\u003e5.9L \u0026amp; 6.7L Cummins Diesel\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003eSKU: FPE-CLNTBYPS-CUMMINS-SER-KIT | Vendor: XDP\u003c\/p\u003e","brand":"XDP","offers":[{"title":"Default Title","offer_id":54611806454052,"sku":"FPE-CLNTBYPS-CUMMINS-SER-KIT","price":27.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0975\/7202\/8708\/files\/fpe-clntbyps-cummins-ser-kit_1.jpg?v=1781290151"},{"product_id":"03-c-ram-heater-core-replacement-hose-and-fitting","title":"03-C RAM HEATER CORE REPLACEMENT HOSE AND FITTING","description":"\u003ch2\u003eHeater Core Replacement Hose \u0026amp; Fitting — 2003+ RAM\u003c\/h2\u003e\u003cp\u003eLeaking or deteriorated heater core hoses and fittings are a common issue on 2003 and newer RAM trucks — leading to coolant loss, reduced cabin heat, and potential engine overheating. This direct-fit replacement hose and fitting kit from Fleece restores a proper, leak-free connection to your heater core, getting your heat back and protecting your cooling system.\u003c\/p\u003e\u003ch3\u003eKey Features\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eDirect-Fit Replacement\u003c\/strong\u003e — Designed specifically for 2003-present RAM trucks for a straightforward, no-modification installation\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eStops Coolant Leaks\u003c\/strong\u003e — Replaces cracked, deteriorated, or leaking factory heater core hoses and fittings\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRestores Cabin Heat\u003c\/strong\u003e — Ensures proper coolant flow through the heater core for full heating system function\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eProtects Cooling System\u003c\/strong\u003e — Prevents coolant loss that can lead to engine overheating and damage\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eQuality Construction\u003c\/strong\u003e — Built by Fleece Performance Engineering for long-term durability and reliability\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFitment\u003c\/h3\u003e\u003cul\u003e\u003cli\u003e2003-Present RAM 2500 \u0026amp; 3500\u003c\/li\u003e\u003c\/ul\u003e\u003cp\u003eVendor: Fleece\u003c\/p\u003e","brand":"XDP","offers":[{"title":"Default Title","offer_id":54611806519588,"sku":"FPE-CUMM-HCL-0324","price":69.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0975\/7202\/8708\/files\/fpe-cumm-hcl-0324_43046215-3d22-427b-87ab-af6ea3dbc819.jpg?v=1781288596"},{"product_id":"985-18-cummins-59l67l-spring-retainer-set","title":"98.5-18 CUMMINS 5.9L\/6.7L SPRING \u0026 RETAINER SET","description":"\u003ch2\u003eCummins 5.9L\/6.7L Valve Spring \u0026amp; Retainer Set — 1998.5–2018\u003c\/h2\u003e\u003cp\u003eWhen you're building power or refreshing a high-mileage Cummins, the valve springs and retainers are not a place to cut corners. This Spring \u0026amp; Retainer Set is engineered for the 5.9L and 6.7L Cummins across a wide range of applications — providing the valve train stability needed to support aggressive camshaft profiles, higher RPM operation, and elevated performance builds.\u003c\/p\u003e\u003ch3\u003eKey Features\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eUpgraded Valve Springs\u003c\/strong\u003e — Higher spring pressure for improved valve control at elevated RPMs and under aggressive tune conditions\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMatched Retainer Set\u003c\/strong\u003e — Precision-matched retainers ensure proper spring seating and long-term valve train reliability\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBroad Fitment\u003c\/strong\u003e — Compatible with 1998.5–2018 Cummins 5.9L and 6.7L engines across multiple RAM applications\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePerformance \u0026amp; Rebuild Ready\u003c\/strong\u003e — Ideal for engine refreshes, performance builds, and high-mileage replacements\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eComplete Set\u003c\/strong\u003e — Includes all springs and retainers needed for a full engine installation\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFitment\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e1998.5–2018 Dodge\/RAM 2500 \u0026amp; 3500\u003c\/li\u003e\n\u003cli\u003e5.9L \u0026amp; 6.7L Cummins Diesel\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003eSKU: FPE-34797 | Vendor: XDP\u003c\/p\u003e","brand":"XDP","offers":[{"title":"Default Title","offer_id":54611816448292,"sku":"FPE-34797","price":499.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0975\/7202\/8708\/files\/image4_1.jpg?v=1781213552"},{"product_id":"cummins-coolant-bypass-kit-w-stainless-steel-braided-line","title":"CUMMINS COOLANT BYPASS KIT  W\/ STAINLESS STEEL BRAIDED LINE","description":"\u003ch2\u003eFleece Coolant Bypass Kit w\/ Stainless Steel Braided Line — Cummins 5.9L\u003c\/h2\u003e\u003cp\u003eEliminate one of the most notorious failure points on the 5.9L Cummins with the Fleece Coolant Bypass Kit. This premium kit reroutes coolant flow away from the factory EGR cooler, preventing coolant contamination and protecting your engine from costly damage — and it comes with a stainless steel braided line for added durability and a clean, professional finish.\u003c\/p\u003e\u003ch3\u003eKey Features\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eStainless Steel Braided Line\u003c\/strong\u003e — Premium SS braided hose for superior durability, heat resistance, and a clean under-hood appearance\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEGR Cooler Bypass\u003c\/strong\u003e — Removes the factory EGR cooler from the coolant circuit, eliminating a common and expensive failure point\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePrevents Coolant Contamination\u003c\/strong\u003e — Stops coolant from entering the intake if the EGR cooler cracks or fails\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eProtects Engine Internals\u003c\/strong\u003e — Reduces the risk of hydrolocking and catastrophic engine damage from coolant intrusion\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eComplete Kit\u003c\/strong\u003e — Includes all necessary hardware, fittings, and braided line for a clean, professional installation\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFitment\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e2003–2004 Dodge RAM 2500 \u0026amp; 3500\u003c\/li\u003e\n\u003cli\u003e5.9L Cummins Diesel\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003eSKU: FPE-CLNTBYPS-CUMMINS-MAN-SS | Vendor: XDP\u003c\/p\u003e","brand":"XDP","offers":[{"title":"Default Title","offer_id":54611816612132,"sku":"FPE-CLNTBYPS-CUMMINS-MAN-SS","price":379.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0975\/7202\/8708\/files\/fpe-clntbyps-cummins-man-ss.jpg?v=1781207764"},{"product_id":"2003-2005-cummins-coolant-bypass-kit","title":"2003-2005 CUMMINS COOLANT BYPASS KIT","description":"\u003ch2\u003eCoolant Bypass Kit | 2003–2005 Dodge\/Ram Cummins 5.9L\u003c\/h2\u003e\u003cp\u003eStop injector cup failures before they start with the Fleece Performance Coolant Bypass Kit for the 2003–2005 Dodge\/Ram 2500\/3500 Cummins 5.9L. This kit corrects the factory coolant flow restriction in the cylinder head that allows hot, stagnant coolant to pool around the injector cups — the root cause of one of the most expensive and common failures on the early common rail 5.9L Cummins.\u003c\/p\u003e\u003ch3\u003eThe Problem This Kit Solves\u003c\/h3\u003e\u003cp\u003eEarly common rail 5.9L Cummins engines (2003–2005) are particularly susceptible to injector cup erosion due to inadequate coolant circulation in the head. As coolant stagnates around the cups, localized overheating accelerates corrosion and erosion of the cup sealing surface. Once a cup fails, coolant enters the combustion chamber and fuel system — leading to white smoke, misfires, hydrolocking, and a full head repair bill. The Fleece coolant bypass kit keeps coolant moving continuously, dramatically reducing this risk.\u003c\/p\u003e\u003ch3\u003eFeatures\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003eCorrects factory coolant flow restriction in the cylinder head\u003c\/li\u003e\n\u003cli\u003eEliminates hot spots around injector cups\u003c\/li\u003e\n\u003cli\u003eDramatically reduces injector cup erosion and failure risk\u003c\/li\u003e\n\u003cli\u003ePrevents coolant intrusion into the combustion chamber and fuel system\u003c\/li\u003e\n\u003cli\u003eComplete kit with all hardware needed for installation\u003c\/li\u003e\n\u003cli\u003eSpecifically engineered for the 2003–2005 5.9L Cummins application\u003c\/li\u003e\n\u003cli\u003eFrom Fleece Performance — a leader in Cummins reliability and performance\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFitment\u003c\/h3\u003e\u003cul\u003e\u003cli\u003e2003–2005 Dodge Ram 2500\/3500 Cummins 5.9L Common Rail\u003c\/li\u003e\u003c\/ul\u003e\u003cp\u003eIf you own a 2003–2005 5.9L Cummins, this is not an if — it’s a when. Install the Fleece coolant bypass kit now and avoid the most preventable failure on the platform.\u003c\/p\u003e","brand":"Fleece","offers":[{"title":"Default Title","offer_id":54611892076836,"sku":"FPE-CLNTBYPS-CUMMINS-0305","price":379.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0975\/7202\/8708\/files\/fpe-clntbyps-cummins-0305_1.jpg?v=1781123994"},{"product_id":"2003-2007-cummins-coolant-bypass-kit","title":"2003-2007 CUMMINS COOLANT BYPASS KIT","description":"\u003ch2\u003eCoolant Bypass Kit | 2003–2007 Dodge\/Ram Cummins 5.9L\u003c\/h2\u003e\u003cp\u003eProtect your 5.9L Cummins from premature injector cup and cylinder head failures with the Fleece Performance Coolant Bypass Kit. Designed for 2003–2007 Dodge\/Ram 2500\/3500 trucks, this kit reroutes coolant flow to eliminate the factory design flaw that allows hot, stagnant coolant to sit around the injector cups — one of the leading causes of cup erosion, coolant contamination, and catastrophic head damage on the 5.9L common rail Cummins.\u003c\/p\u003e\u003ch3\u003eWhy You Need a Coolant Bypass Kit\u003c\/h3\u003e\u003cp\u003eThe 2003–2007 5.9L Cummins has a known issue where coolant flow through the cylinder head becomes restricted and stagnant around the injector cups. This localized overheating accelerates injector cup erosion, allowing coolant to enter the combustion chamber and fuel system. Left unaddressed, it leads to white smoke, hydrolocking, and expensive head repairs. The Fleece coolant bypass kit keeps coolant moving, reducing heat soak and dramatically extending the life of your injector cups and head gasket.\u003c\/p\u003e\u003ch3\u003eFeatures\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003eEliminates stagnant coolant flow around injector cups\u003c\/li\u003e\n\u003cli\u003eReduces localized overheating in the cylinder head\u003c\/li\u003e\n\u003cli\u003eExtends injector cup and cylinder head life\u003c\/li\u003e\n\u003cli\u003eHelps prevent coolant contamination of the fuel system\u003c\/li\u003e\n\u003cli\u003eComplete kit with all necessary hardware for installation\u003c\/li\u003e\n\u003cli\u003eFrom Fleece Performance — a trusted name in Cummins performance and reliability\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFitment\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e2003–2004 Dodge Ram 2500\/3500 Cummins 5.9L CR\u003c\/li\u003e\n\u003cli\u003e2004.5–2007 Dodge Ram 2500\/3500 Cummins 5.9L CR\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003eThis is one of the best preventive maintenance upgrades you can do on a 5.9L common rail Cummins. Don't wait for injector cup failure — install the bypass kit and keep your engine protected.\u003c\/p\u003e","brand":"Fleece","offers":[{"title":"Default Title","offer_id":54611892207908,"sku":"FPE-CLNTBYPS-CUMMINS-MAN","price":379.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0975\/7202\/8708\/files\/FPE-CLNTBYPS-CUMMINS-MAN_1_thmb.jpg?v=1781123235"}],"url":"https:\/\/autodieselsystems.com\/collections\/2003-2004-5-9l-cummins-engine-internals.oembed","provider":"Auto Diesel Systems","version":"1.0","type":"link"}