Best Cummins Radiators 2021 – Reviews and Buying Guide

If you own a RAM or Dodge RAM 2500 or 3500 pickup truck with a Cummins 5.9L or 6.7L turbo diesel engine, then you know just how powerful of a beast it is. Everything from the 1,000 pound-feet of pure, unadulterated diesel torque to the raw 400 horsepower hidden under the hood is built for rugged performance.

It goes without saying that a powerhouse like this needs a heavy-duty cooling system specifically designed for Dodge RAM truck engines. Without it, your vehicle will keep overheating, which can, in turn, cause extensive damage to the engine.

We tested the best Cummins radiators on the market to bring you our top picks for 5.9L and 6.7L engines.

CoolingSky Aluminum RadiatorCoolingMaster 2-Row Aluminum RadiatorCoolingMaster 3-Row Aluminum Radiator
Best OverallBest 2-Row OptionBest 3-Row Alternative

Core size

27.0 x 28.1 in.26.7 x 32.9 in.27.0 x 28.1 in.


1.97 / 1.97 in.1.75 / 1.75 in.1.97 / 1.97 in.



Compatible with

Diesel 5.9L / 6.7L CumminsDiesel 6.7L CumminsDiesel 5.9L / 6.7L Cummins
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How We Tested and Compared These Products

First off, we were only interested in Cummins radiators from top brand manufacturers. CoolingSky, CoolingMaster, and ZRJM were top on our list.

The Mishimoto performance radiator was equally good, although it ranked fifth in our tests.

Next, they had to be compatible with 2500 and 3500 diesel 5.9L and 6.7L Cummins engines for RAM and Dodge RAM trucks.

Finally, we were interested in how efficient the cooling system was. For this reason, we only tested 2-row and 3-row aluminum radiators and their effect on the engine functions.

Our Pick: CoolingSky Aluminum Radiator – Best Overall





  • Core size:0 x 28.1 in.
  • Inlet/Outlet: 97 / 1.97 in.
  • Rows: 3
  • Compatible with: Diesel 5.9L / 6.7L Cummins

The CoolingSky aluminum radiator is undoubtedly the best-performing cooling system for Cummins engines we’ve come across. It is remarkably lightweight and made of 100% brazed aluminum with a nicely polished end tank. Its special top tank design maximizes cooling efficiency tremendously.

When we put it to the test, the temperature gauge indicated a 25-degree drop in the outlet heat. This reading was significantly lower than what we had been accustomed to with the original radiator (OEM) that came with the vehicle. We did not expect to see such a high level of cooling efficiency. It was 35% less than the OEM factory radiator.

This remarkable cooling power was evident in the engine’s performance. It allowed us to push the engine to the limit and unlock its full potential without worrying about it overheating. Its performance was nothing short of outstanding.

CoolingSky’s cooling efficiency can be attributed to its 3-row design and the multi-louvered fins that guarantee optimum function even in extreme weather conditions. We also liked the TIG-welded, full aviation-grade aluminum construction. You can clearly tell it was built to last. Even the die-stamped tanks have extra reinforcement to enhance their rigidity.

The radiator comes with a mounted billet filler neck to ensure the cooler system remains pressurized, which in turn raises the boiling point of the coolant and pushes through the system.

All in all, the efficient and innovative design of this radiator, alongside its high-quality construction, explains why it is a top choice for many owners of diesel Cummins Dodge RAM trucks.

  • Delivers maximum cooling efficiency even in extreme weather conditions
  • TIG-welded using aviation-grade craftsmanship
  • Die-stamped tanks are built with extra reinforcement
  • The 3-row design guarantees optimum cooling efficiency
  • The machined-billet neck provides excellent pressure control
  • The fit is a little snug in the 2500 Cummins
CoolingSky 55MM 3 Row All Aluminum Radiator for 2003-2009 Dodge...
41 Reviews
CoolingSky 55MM 3 Row All Aluminum Radiator for 2003-2009 Dodge...
  • Built with high density multi-louvered fins for maximum cooling...
  • Full aviation-aluminum craftsmanship, 100% welded by TIG
  • Reinforced die-stamped tanks for added rigidity, machined-billet...


Best Alternatives

CoolingMaster 2-Row Aluminum Radiator – Best 2-Row Option

CoolingMaster 2 Row Aluminum Radiator




  • Core size:7 x 32.9 in.
  • Inlet/Outlet: 75 / 1.75 in.
  • Rows: 2
  • Compatible with: Diesel 6.7L Cummins

Next up was the CoolingMaster 2-row aluminum radiator. According to the manufacturer, it should fit 2500, 3500, and 4500 6.7L Cummins diesel engines. For our test, we fitted it on the 3500 6.7L engine in our Dodge RAM.

Physically, it looked quite similar to the CoolingSky radiator. Functionally, this unit is a 2-row radiator, so we obviously did not expect the same level of performance we got with the CoolingSky.

Although it is quite lightweight, it feels exceptionally sturdy. This is a far cry from some of the flimsy radiators we tested when narrowing our list. We also liked that it had a TIG-welded end tank as opposed to an Epoxy weld. Epoxy has lower overall tensile strength.

It fit perfectly in our 2010 Dodge RAM 3500 6.7L Cummins. We hit the road to find out how this cooling system would hold up in the real world. We had the engine running for about an hour while keeping an eye on the temperature gauge.

The results were impressive. The outlet heat output had a 20-degree drop, which was a 28 percent improvement on the OEM temperature.

The CoolingSky radiator is made of 5057 aviation-grade aluminum with a simple raw metallic finish. The brass petcock drain looks quite similar to the OEM, which we thought was a nice touch for easier maintenance.

All in all, this 2-row aluminum radiator is a solid choice for any RAM and Dodge RAM truck owner with a 2500 or 3500 diesel 6.7L Cummins engine under the hood.

  • Made of aviation-grade aluminum
  • Super-efficient cooling system
  • TIG-welded (not Epoxy)
  • It comes with a radiator cap
  • Great value for the money
  • Not compatible with 5.9L Cummins engines
CoolingMaster 2 Row Aluminum Radiator For 2010-2012 Dodge Ram...
  • Overall Size: 36.15 inch x 34.15 inch ; Core Size: 26.7 inch x 32.9...
  • Inlet & Outlet: 1.75 inch & 1.75 inch
  • Tank Wall Thickness: 0.08 inch


CoolingMaster 3-Row Aluminum Radiator – Best 3-Row Alternative

CoolingMaster 3 Row Aluminum Radiator Compatible


No products found.


  • Core size:0 x 28.1 in.
  • Inlet/Outlet: 97 / 1.97 in.
  • Rows: 3
  • Compatible with: Diesel 5.9L / 6.7L Cummins

CoolingMater 3-row aluminum radiators are the slightly more superior version of the 2-row radiators. While they both look the same, the radiator core size of the 3-row variant is a little taller and narrower compared to the 2-row variant. Nonetheless, it fits the 6.7L Cummins as well as the 5.9L engines.

This radiator is made of 5057 aviation-grade aluminum with a raw metallic finish that’s quite easy on the eye. The filler neck, which also comes with a radiator cap, is CNC machined to ensure the cooling system remains pressurized. This enhances the system’s cooling efficiency by reducing the boiling point of the coolant inside.

When we put it to the test, we found that its performance was more or less at par with that of the CoolingSky system. It recorded a 23-degree drop in the outlet temperature, which was just 2-degrees less than what we got with CoolingSky. Either way, that was pretty impressive.

If you’re looking to get a 3-row radiator for your RAM or Dodge RAM truck, and for some reason, are unable to get the CoolingSky, this would be the ideal upgrade. It will serve you just as well.

  • Outstanding temperature regulation
  • Compatible with a wide range of Cummins engines
  • Made of aviation-grade aluminum
  • CNC-machined radiator cap and filler neck
  • Compatible with 5.9L and 6.7L Cummins
  • It fits a little snug in the 2003-2007 2500 5.9L diesel engines
CoolingMaster 3 Row Aluminum Radiator Compatible with 2003-2009...
3 Reviews
CoolingMaster 3 Row Aluminum Radiator Compatible with 2003-2009...
  • Core Size: 27.0"x 28.1" ; Over Size: 35.5" x 30.5"
  • Inlet/Outlet: 1.97"/1.97"
  • Interchange Part Number: 2711 CU2711 RAD2711 DPI2711 ; Part Numbers:...


ZRJM Aluminum Radiator – Best Value

ZRJM Aluminum Radiator FITS


No products found.


  • Core size:0 x 28.25 in.
  • Inlet/Outlet: 75 / 1.75 in.
  • Rows: 2
  • Compatible with: Diesel 5.9L / 6.7L Cummins

Cummins radiators aren’t exactly cheap. That said, it is possible to find quality products from reputable manufacturers without denting your wallet when upgrading your RAM cooling system. ZRJM aluminum radiators combine everything you want in a cooling system designed for 5.9L and 6.7L Cummins engines with diesel applications.

First impressions: It looks great. The glossy metallic aluminum finish looks and feels premium. We would go as far as to say – it looks better than all the other Cummins radiators we tested, most of which had a raw aluminum finish. It is also quite lightweight, which is a must-have feature for efficient cooling systems.

It had a direct fit on the 3500 6.7L engine in our Dodge RAM, which made installation effortless. We drove around for an hour to find out how well this radiator works and if the affordable price point meant cutting corners as far as cooling efficiency goes. We were pleasantly surprised by the results.

There was a 17-degree temperature drop in the outlet heat, which was quite impressive for a radiator in its class. We would have been happy with a 15-degree improvement over the OEM, but the fact that it cooled the engine by an extra two degrees was nothing short of outstanding.

All in all, for a budget radiator, the ZRJM cooling system offers excellent value for the money.

  • Nice, polished, metallic finish
  • Made of high-quality aluminum
  • Excellent value for the money
  • Efficient temperature reduction
  • Backed by a one-year warranty
  • It is not TIG welded

No products found.

How to Choose the Best Cummins Radiators – Buying Guide


A RAM pickup truck

Not all Cummins radiators are created equal. We’ve come across our fair share of aluminum cooling systems that do nothing to keep engine temperatures under control. Here are some helpful tips to keep in mind when looking for a direct replacement.


If the Cummins radiator you’re looking to buy is made of something other than aluminum, you’ll be in for a rude shock a few months down the line. Aluminum is the go-to material for radiators because of its durability, its rust and corrosion resistance, and the fact that it is ultra-lightweight.

Radiators made of aviation-grade aluminum tend to outlast the ones that aren’t. Bonus points if they are TIG-welded as opposed to having an Epoxy weld. TIG-welds have higher overall tensile strength.

Radiator Rows

Engine coolant in a radiator flows through tiny tubes located over multi-louvered fins. They have an electric fan in a fan shroud blowing over them to dissipate the heat. The more rows you have, the larger the surface area over which the fluid can flow. This translates to faster and more efficient cooling even with low coolant capacity.

Keep in mind that more rows don’t equate to faster cooling. The number of rows present on the radiator needs to balance out the tube width. A radiator with one-inch tubes spread over two rows will cool the engine faster than one with 5/8-inch radiator tubes spread over three rows.

More rows also mean a thicker aluminum core like what you would find in a stock radiator. This can get in the way of airflow, the subsequent cooling capability, and fuel economy.

Flow Direction

There are generally two types of radiators based on the direction of their fins: Crossflow and downflow.

In a crossflow radiator, the fins run from side to side, while those in a downflow radiator run up and down. The inlet hose in a crossflow cooling system is at the top side of one end and has the engine coolant running horizontally until it gets to the outlet at the bottom of the other end.

On the other hand, the inlet hose in a downflow radiator is at the top, and the coolant flows down until it exists via the bottom outlet.

Crossflow Cummins radiators offer better cooling efficiency compared to their downflow counterparts. When shopping for a new radiator for your RAM or Dodge RAM truck, keep this in mind.

Radiator Cap

Ensure the radiator you buy comes with a CNC-machined radiator cap with a positive pressure head and filler neck. The cap needs to be able to remain vacuum-sealed to ensure the cooling system remains pressurized. This helps circulate the water or coolant and enhances the system’s cooling efficiency by reducing the boiling point of the coolant inside.

The radiator cap should have a minimum PSI rating of 15. If the positive pressure is lower than that, the engine will inevitably overheat.


Not all Cummins radiators come with a petcock drain. Only a few, like the CoolingMaster 2-Row Aluminum Radiator, have one. While it is not a mandatory requirement, petcock drains make routine radiator maintenance more convenient.

If you’ve ever had a case of metallic debris fragments floating around in the cooling liquid, you know exactly what we mean.

The drain plug will typically be located at the bottom of the radiator. Always check to ensure it is tightly sealed to prevent a potential leak.


What Cummins radiator should I get for my Dodge RAM truck?

It depends on the model year. A CoolingSky Aluminum Radiator and CoolingMaster 3-Row Aluminum Radiator are compatible with most 2003-2012 pickup trucks with a 2500 and 3500 Cummins 5.9L or 6.7L engine.

Which is better between a 2-row and 3-row radiator?

The number of rows needs to make sense for the size of the tubes it has. While more rows generally translate to faster cooling, this may not always be the case. For instance, a radiator with one-inch tubes spread over two rows will cool the engine faster than one with 5/8-inch tubes spread over three rows. If they both have similar-sized tubes, go for the radiator with the higher row count.

What is the best material for a Cummins radiator?

Aluminum is the preferred material for Cummins radiators. It is lightweight and more efficient compared to the copper-brass variety. Ensure the cooling system you get is made of aviation-grade aluminum like what you find in the CoolingSky radiator. It is one of the most durable systems on the market right now.


There you have it – the best Cummins radiators for 2021. While all the products we’ve reviewed here would be an excellent choice for your engine, CoolingSky has a special place in our hearts and our Dodge RAM truck. Its cooling efficiency is unlike anything else we’ve come across.