OEM Standard Direct Replacement Corrosion-Resistant Bypass Valve Assembly for

Precision-engineered bypass valve assembly regulates coolant or oil flow in ISUZU 4HK1 engines, maintaining optimal operating temperature and pressure for reliable performance.

• OE Quality: Manufactured to strict ISUZU dimensional and material specifiions for perfect fit and function
• Precision Engineering: Calibrated valve mechanism ensures accurate fluid flow regulation
• Durable Construction: High-grade cast housing withstands extreme temperatures and pressures
• Reliable Spring Mechanism: Consistent valve operation throughout the service life
• Corrosion-Resistant: Treated surfaces resist rust and degradation from coolant or oil exposure
• Restores Temperature Control: Eliminates overheating or underheating caused by faulty bypass valves
• Maintains Fluid Pressure: Ensures proper system pressure for optimal engine protection
• Direct Replacement: Simple installation with no modifiions required
• Long Service Life: Engineered to withstand the rigors of heavy-duty commercial operation
• Prevents Engine Damage: Protects against overheating-related failures and costly repairs

This bypass valve assembly is specifically designed for ISUZU medium-duty trucks. Common appliions include:

• ISUZU NPR66 – Medium-Duty Trucks
• ISUZU NPR70 – Medium-Duty Trucks
• ISUZU NPR75 – Medium-Duty Trucks

• ISUZU 4HK1 – 4-Cylinder, Inline Diesel
  • Displacement: 5.2L (5193cc)
  • Turbocharged, Intercooled
  • Widely used in NPR series trucks

Professional installation recommended for proper system integrity:

1. Relieve system pressure – Drain coolant (or relieve oil pressure) as applicable for your system
2. Loe the bypass valve housing – Identify the valve assembly on the engine block or housing
3. Clean the surrounding area – Remove dirt and debris to prevent contamination
4. Remove the old valve assembly – Unbolt and carefully remove the old valve assembly
5. Clean mounting surfaces – Remove old gasket material and clean the sealing surfaces thoroughly
6. Inspect the housing bore – Check for scoring, corrosion, or damage to the valve bore
7. Prepare the new assembly – Install new O-rings or gaskets supplied with the valve (if applicable)
8. Apply sealant if required – Use approved sealant on threads or gasket surfaces per manufacturer spec
9. Install the new bypass valve – Position the new assembly and torque mounting bolts to specifiion
10. Reconnect hoses/lines – Reattach any coolant or oil lines to the valve housing
11. Refill coolant/check oil – Refill cooling system or check oil level per manufacturer requirements
12. Bleed air from system – Bleed air from the cooling system if applicable
13. Check for leaks – Start the engine and inspect for any fluid leakage around the valve
14. Verify operation – Allow engine to reach operating temperature and confirm proper valve function

• Material Verifiion: Confirms housing and internal component materials meet OE specifiions
• Dimensional Inspection: Housing and valve dimensions verified against OEM tolerances
• Spring Tension Testing: Valve spring force measured to ensure correct opening and closing characteristics
• Calibration Verifiion: Valve operation verified at specified temperature or pressure thresholds
• Seal Integrity Check: Sealing surfaces and gaskets inspected for leak-proof performance
• Surface Finish Inspection: Machined surfaces checked to ensure proper sealing and operation
• Visual Inspection: 100% checked for casting defects, machining flaws, or damage
• Packaged Safely: Protected and securely boxed to prevent damage during transit

• Neutral export packing or customized packaging available
• Carton or wooden case for safe transportation
• Fast delivery for stock items
• Shipping by Express Air or Sea

For pricing, availability, or bulk purchase of the Bypass Valve Assy 8970135662 8-97013566-2 For ISUZU NPR 4HK1 Engine Truck Parts, please contact our sales team for a competitive quote and expert technical support.