Cummins NH855 Fresh Water Pump & Cooling System Catalog

The Cummins NH855 engine is renowned for its durability and ability to handle continuous-duty workloads in marine and industrial applications. At the heart of this engine’s reliability is its fresh water cooling system, which regulates operating temperatures and prevents overheating.

The fresh water pump, along with thermostats, gaskets, belts, hoses, and clamps, ensures the NH855 maintains stable thermal performance. At Diesel Pro Power, we provide OEM-quality cooling system parts designed to fit Small Cam and Big Cam NH855 configurations, with full CPL compatibility where required.

Fresh Water Pumps for Cummins NH855

Fresh Water Pump – Big Cam I & II Engines

• Impeller: 4 1/2"

• Design: Vented

• Pulley: 4 11/16" multi-groove

• Application: Big Cam I & II NH855 engines

This pump is engineered for early Big Cam designs, maintaining consistent coolant circulation under heavy-duty marine propulsion or industrial applications.

Fresh Water Pump – Big Cam IV Engines

• Impeller: 4 1/2"

• Design: Vented

• Pulley: 4 1/4" multi-groove

• Application: Big Cam IV NH855 engines

• Compatible CPL Numbers:
  9910, 991, 1576, 1502, 1215, 1381, 769, 1383, 1436, 633, 1204, 1145, 1193, 5520, 909, 700, 849, 413, 614

This pump is the correct choice for Big Cam IV platforms, ensuring the proper pulley alignment and coolant flow designed for these later-series engines. Matching by CPL number ensures precise fitment and long-term reliability.

Fresh Water Pump – Small Cam Engines

• Impeller: 5 1/4"

• Design: Non-vented

• Pulley: 2-groove

• Application: Small Cam NH855 and NT855 engines

Optimized for Small Cam applications, this pump’s larger impeller provides strong coolant circulation, supporting steady engine temperatures even during continuous full-load operation.

Thermostats for Cummins NH855 Cooling Systems

Thermostats regulate coolant flow between the engine and radiator or heat exchanger, maintaining optimal operating temperatures.

• 180°F Thermostat – Standard option for NH855 and NT855 engines.

• 185°F Thermostat – Designed for Big Cam engines, allows slightly higher operating range for efficiency.

• 173°F Thermostat – Lower-temperature option for marine and heavy industrial duty where cooler operation is preferred.

Using the correct thermostat prevents overheating while ensuring the engine reaches its intended operating temperature for efficiency and reduced wear.

Gaskets & Seals for NH855 Water Pumps

Reliable sealing is critical for maintaining pressure and preventing coolant leaks in the NH855 system.

• Water Inlet Connection Gasket – Prevents leaks at pump inlet.

• Mounting Gasket – Provides tight sealing between pump and engine block.

• Outlet O-Ring Seal – Ensures leak-free connection at pump outlet.

High-quality gaskets and seals help extend the life of the pump and protect against coolant loss under heavy-duty operating conditions.

Fan Drive Belts for NH855

The NH855 requires two fan drive belts per engine, which power both the cooling fan and the water pump. Built for durability, these belts maintain consistent operation under tension, vibration, and high-heat environments. Regular inspection and replacement are recommended to prevent sudden overheating.

Radiator Cleaner & Cooling System Maintenance

Over time, scale and debris can build up in the NH855 cooling passages, reducing efficiency. A radiator cleaner helps flush contaminants, restoring full coolant flow. Routine flushing is especially important in marine engines exposed to varying water qualities and industrial engines running in dusty or harsh environments.

Temperature Switch for NH855 Cooling Systems

The temperature switch monitors coolant temperature and activates warnings or fans when overheating occurs.

• Activation point: 205°F

• Thread size: 1/2” NPT

• Compatible across Cummins, Detroit Diesel, and Caterpillar cooling systems

This ensures the NH855 remains protected against thermal stress.

Silicone Coolant Hoses for Cummins NH855

Silicone hoses provide superior durability compared to standard rubber, resisting heat, pressure, and chemical degradation. Available in 1-foot lengths, these hoses come in a wide range of diameters to fit various NH855 coolant system layouts:

• 3/4"

• 1"

• 1 3/4"

• 1 7/8"

• 2"

• 2 1/8"

• 2 1/4"

• 2 3/8"

• 2 1/2"

• 2 3/4"

• 3"

• 3 1/2"

• 4"

Their flexibility and strength make them ideal for marine and stationary engine cooling systems exposed to extreme operating conditions.

Hose Clamps for NH855 Cooling System

To secure hoses under high-pressure coolant flow, stainless steel clamps are available in multiple ranges:

• Small diameter clamps – For bypass and fuel line applications.

• Medium clamps – For mid-sized coolant connections.

• Large clamps – For main radiator and water pump hoses.

These clamps ensure leak-free operation even under vibration and thermal cycling.

Why Diesel Pro Power is the Best Source for NH855 Cooling System Parts

• Focused Expertise: Specialists in Cummins NH855 and NT855 platforms.

• Global Reach: Fast worldwide delivery to over 180 countries.

• Proven Trust: Over 40,000 satisfied customers worldwide.

• OEM-Quality Standards: All parts meet or exceed Cummins specifications.

• Comprehensive Inventory: Covering water pumps, thermostats, gaskets, belts, hoses, clamps, and more.