Water Pump Discussion – Plastic or Metal Impeller?

Plastic impeller or metal impeller: that is the question.  When talking to customers about water pumps, the common perception is that a water pump with a plastic impeller is not desired.  This also tends to be the consensus at website forums and Facebook communities.  What do they know that we might have missed?

The Cummins Water Pump and the Plastic Impeller:

Today, every Cummins (or Mopar, they are re-boxed Cummins items) water pump offered for a Ram/Cummins application uses a plastic impeller. We do not have a good answer for why Cummins has moved away from a stamped steel metal impeller (circa 2018), but production cost savings more than likely played a role.

We know that you want the “old reliable.” Then again, your dad was slow to change from bias-ply tires to “them fancy radial tires.” In the meantime, well, Cummins/Mopar water pumps have a plastic impeller. You don’t have a choice.

The Gates Water Pump and Plastic or Metal Impeller:

The Gates products are a mix of plastic and metal impellers.  Gates uses plastic for years 2007.5-2012 (part number 42291).  They use metal for all other years. These water pumps are a great value for the money.

Gates Water Pump – Part Number 42291

The Bullet Proof Diesel Water Pump:

In 2023 we introduced the Bullet Proof Diesel, billet aluminum, water pump to our offerings.  They made it simple for the audience, one part number is used for all years, 1989-current 2022 (part number BP90201228). From the larger bearings, aluminum impeller and pulley designed to help cool the bearing, this is, by far, the best water pump available for our application.  Bullet Proof Diesel uses the newer smaller diameter pulley.  In all their testing and time since the pump’s release, no problem has been found with belt tension due to the smaller pulley.  This will cause the water pump to spin faster and move more coolant.

Although a newer product for us, Bullet Proof Diesel has been offering this water pump long enough to have an impressive track record.  This is for the customer who is wanting to keep their truck for many years and does not mind spending more for a better product.  The price is comparable to the Cummins part for years 2019-current. The price is substantially more expensive than a Gates product.

Bullet Proof Diesel’s water pump for 1989-2022 Ram Cummins 5.9L and 6.7L.


It is difficult to do a year-to-year price comparison of the Cummins versus Gates pricing. However, the Gates part numbers are typically about half (or more) the price of the Cummins/Mopar offering. Yet, we don’t see complaints of “half the service life.”

Our Advice:

If the water pump were extremely difficult to change, the advice would be to buy the best quality/longest lasting product. But the water pump is an item that is easy to service. Plastic or metal?  What does it matter? Both style impellers push water. It would be different if plastic impellers were new to the automotive marketplace. They’re not.

Further advice, pocket the money. Take the wife/girlfriend out to dinner, purchase some other accessories for the truck, fill up the tank for a road trip.

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