The Cummins 5.9 liters (360.0 cu in) ISB (Interact System B) uses a straight-six multi-valve pushrod engine design. The engine displaces 5,883 cubic cm (359.0 cu in), with a 102.0 mm (4.02 in) cylinder bore and 120.0 mm (4.72 in) piston stroke. This model uses a turbocharger to increase output for high-compression (17.2:1 in recent versions) diesel.
List of Top-Rated Water Pumps for 5.9 Cummins Comparison Table:
| Photo | Model | Year | Impeller | Description |
|---|---|---|---|---|
 | Gates 43034 Water Pump | 1989-1998 | Stamped Steel | View on Amazon |
 | G&T Engine Parts AP63532 | 2003-2007 | Cast Steel | View on Amazon |
 | Gates 43526 | 1989-2007 | Cast Steel | View on Amazon |
 | ACDelco 252-318 Professional Water Pump Kit | 1994-2007 | Billet Aluminum | View on Amazon |
 | Rareelectrical 18-1109B1 | 1989-1998 | Cast Steel | View on Amazon |
The body is made of all-iron with forged steel connecting rods, an assembled camshaft, and a cast aluminum intake manifold. The 5.9 ISB connects to an electronically controlled Robert Bosch GmbH rail fuel injection, Bosch injectors, and a Bosch CP3 high-pressure pump.
Now let’s take a look at the five best water pumps for the 5.9 Cummins engine.
The Water Pumps for 5.9 Cummins Reviews & Buyer’s Guide:
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Gates 43034 Water Pump
Description
Gate 4303 water pump is a pump made and designed with a high level of professionalism. It comes integrated with several components, including a gasket, a steel tube, and a rubber O ring to complete a fitment. You will also like the bypass tube, which is deemed a nice add on to the pump.
Performance
The gate 4303 water pump is popular when it comes to replacing the 5.9 Cummins water pump. Even though the manufacturer produces the pumps on a large scale, they are always low or not in stock following the consumer’s high rate consumptions. This is one sure way the product is doing well by solving people’s problems. It is made of aluminum, steel, and metal, making it quite reliable and resilient.
Features
- OEM style impeller
- Cast iron casing
Recommendations
If you own a dodge B-series (1993-2002), W250 (1989-1993), W350 (1989-1993), Ram (1994-2003), or a Ram 3500 (1994-2003), this would be assumed as the best aftermarket option for you. It has proved its durability over the years. It always meets the buyers’ expectations and recommends moving the coolant via a motor to give it the required operating temperature.
G&T Engine Parts AP63532
Description
Alliant Power #AP63532 Water Pump for Dodge Cummins 2003-2007 5.9L
Performance
This water pump comes with a cast iron housing and a cast steel impeller. It is a very solid product with all mounting gaskets, seals and OEM standards of performance.
This product is used on all 2003-2007 5.9L ISB models.
Features
- Cast iron housing
- Cast steel impeller
Recommendations
A classic quality replacement part for your worn out OEM water pump.
Gates 43526
Description
Gates 43526 Cummins 5.9L water pump for 1998 to 2009
Performance
The Gates® water pumps are fabricated using the cast iron body with a stamped steel impeller. All these pumps are made to OE standards and are easy to install and maintain. The core materials provide you with a low maintenance lifetime of performance.
The cast iron housing and stamped steel impeller come with all seals and gaskets tested for integrity.
Features
- Cast Iron Housing
- Water Pump, O-Ring
- Reverse rotation rotor
- Stamped Steel Impeller
Recommendations
This is a very versatile model, is made of premium stock materials and is a great replacement part.
ACDelco 252-318 Professional Water Pump Kit
Description
An Acdelco professional premium aftermarket water pump is a great pump that circulates coolant through the truck’s radiator and engine system in maintaining proper engine temperature and professional performance. It has some gaskets, seals, and O rings integrated by professionals to guarantee all the necessary parts for smooth installation.
Performance
According to the manufacturer, you can fit it to different vehicles models powered by a 5.9L Cummins, including the Dodge D250 (1989-1993), D350 (1989-1993), Ram 2500 (1994-2009), Ram (1994-2007), W250 (1989-1993), and W350 (1989-1993). You don’t need to mind the installation as the latter comes with a cross-section of the O ring gasket, which means bolting on the new pump is just a simple exercise.
Features
- Epoxy coated electric 12-volt motor
- Anodized billet aluminum 6061 impeller
- Stainless steel motor shaft, jacketed seal, and fasteners
- Draws only 6 Amps
- Hose Adapter Included
Recommendations
It is one of the best water pumps for a replacement out there because of how it features solidly puts together all bearings that are permanently sealed and lubricated to last long.
Rareelectrical 18-1109B1
Description
This is the Rare Electrical Heavy-Duty Water Pump for NH250 AR51360 AR51360RX 252-457
Performance
This is a standard OEM quality aftermarket water pump that comes in an iron cast body with a steel cast impeller. The unit is for 6B motors only 1989-1998 models.
Features
- Cast Iron housing
- Steel Impeller
- OEM/Stock quality
Recommendations
This is the classic OEM style 6BT water pump replacement part, very budget friendly and extremely reliable.
How to Replace a Water Pump?
Replacing a water pump is about 20 minutes of work, and maybe another 10 minutes to check your pressure. I attach a comprehensive video as well as explain it in the text.
- Prepare a clean working area if possible
- Prepare all the tools and parts and a pail for collecting the old water and coolant
- Have new water and coolant ready
- Empty the water and coolant from the system
- Take off the belt (If you want, have a new one ready to replace this too)
- Unbolt the pump housing from the engine block
- Pry off the old pump
- Wipe the engine surface area, don’t score it.
- Prep the new pump, use silicone grease
- Add some Loctite on the bolts
- Bolt it into place
- Restore the belt back into place.
- Input new water and coolant.
- Check the pressure for system integrity
- Start the engine and you are all done.
The 5.9 Cummins was the preferred engine in Dodge Ram pickups till 2007.5 when it was replaced by the Cummins 6.7L engine.
The Cummins 5.9L ISB has gone through some changes since it was first introduced in 1989, and there were three generations of this motor.
Generation 1: 1989-1993, 5.9L (359 in3) inline 6-cylinder, 4-stroke, Turbocharged / Aftercooled (MY91.5+) delivered 160HP @ 400 tq, VE-Rotary pump, 12V valves.
Generation 2 – 1994-2002, 5.9L (359 in3) inline 6-cylinder, 4-stroke, Turbocharged / Aftercooled
| Year | Peak hp | Torque (lb-ft) | Pump | Valves |
|---|---|---|---|---|
| 1994-1997 | 175 | 420 | P-7100 | 12V |
| 1998 | 235 | 460 | P-7100 | 12V |
| 1998.5-2000 | 235 | 460 | VP44 | 24V |
| 2001-2002 | 245 | 505 | VP44 | 24V |
Generation 3 2003-2007, 5.9L (359 in3) inline 6-cylinder, 4-stroke, Turbocharged / Aftercooled (MY91.5+)
| Year | Peak hp | Torque (lb-ft) | Pump | Valves |
|---|---|---|---|---|
| 2003 | 305 | 555 | HPCR | 24V |
| 2004 | 325 | 600 | HPCR | 24V |
| 2005-2006 | 325 | 610 | HPCR | 24V |
| 2007 | 350 | 650 | HPCR | 24V |
Water Pumps
Water pumps are integral key components in a car’s engine performance; they maintain the temperature of the engine by pumping coolant around the engine block, hoses, and radiator. The water pump uses an impeller that is driven by a serpentine belt from the crankshaft pulley. The impeller pumps the water constantly through the engines water jacket that is constructed around the combustion chambers. This constant flow of water maintains the core temperatures from overheating.
The water flows through the engine and heats up as it goes through, it then passes through the radiator that is cooled by the airflow and returns to the water pump for reflow into the engine block once again. This is a very basic circular pumping motion, with its simplicity comes the most cost-effective cooling agent for the engine.
Water Pump Issues
Even while the actual water pump is a very basic device, it does have issues as with all electromechanical units.
Here is a list of the most common problems that water pumps reach:
Worn bearings, these are discovered when you hear a grinding noise and are usually a sign to replace the whole unit. Sometimes you can replace the bearings, but the cost involved is usually equaled that of just replacing the entire pump component.
A water leak originating from the pump housing is a sign that either a gasket or the shaft seal is cracked. Water leaks reduce the effectivity of the pump to push the water and thus lead to overheated engines. When you see your water temperature light turn on, you need to check for a leak in the entire system, including the pump housing. The two variants of a leaking pump housing are different when a shaft seal cracks you need to replace the entire water pump when the gasket cracks you only need to replace the gasket.
Broken impeller blades are a more modern occurring problem with water pumps that are made using plastic impellers. You will notice a vibration originating from the pump housing, and a broken blade will lead to a pump fail and an overheating engine. In this case, just replace the entire pump.
Water Pump Maintenance
A water pump is a very simple device; it can be maintained with a minimum of effort. To start with, if you intend to change the OEM unit, make sure you only purchase a brand pump made from good solid metals. Always make sure the amount of coolant and antifreeze is per manufacturer’s ratios. The coolant acts as a rust inhibitor, and the anti-freeze is only added for cold (minus degree) weather.
