6 Best Electric Cooling Pumps For RV Engine Conversions Nomads Swear By

You’re halfway up a steep grade in the Rockies, the engine you painstakingly swapped into your skoolie is screaming, and you see it—the temperature gauge creeping into the red. A mechanical water pump, tied to your low RPM climb, just isn’t moving enough coolant to keep things stable. This is the exact moment many nomads realize that a robust cooling system isn’t a luxury; it’s the difference between a great memory and a very expensive tow.

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Why Electric Pumps for RV Engine Conversions?

The stock, belt-driven water pump on most engines is a compromise. Its speed is directly tied to engine RPM, which means at idle or low-speed, high-load situations—like crawling through a national park or climbing a mountain pass—you get the least amount of coolant flow right when you need it most. This is a fundamental flaw for a heavy vehicle that lives a life of extremes.

An electric water pump (EWP) decouples coolant flow from engine speed. This gives you consistent, reliable cooling whether you’re idling in desert heat or chugging up a long grade. You can run the pump at full tilt even when the engine is barely turning over. This simple change provides a massive improvement in temperature stability and engine longevity.

Furthermore, electric pumps offer incredible flexibility in a custom engine bay. You aren’t locked into the stock location, which can be a lifesaver when fitting a modern engine into an older chassis. More importantly, many can be programmed to run for a few minutes after you shut the engine down. This eliminates "heat soak," a phenomenon where residual heat boils the stagnant coolant in the cylinder heads, causing long-term damage.

Davies Craig EWP150: The Versatile Workhorse

If there’s one electric pump you’ll see in more high-quality conversions than any other, it’s the Davies Craig EWP150. It hits the perfect sweet spot of performance, reliability, and smart features. Its lightweight nylon construction is surprisingly durable, and its 40-gallon-per-minute (GPM) flow rate is more than enough for the vast majority of V8 and diesel swaps.

What truly sets the Davies Craig system apart is its optional digital controller. This isn’t just a pump; it’s a complete cooling management system. The controller lets you set a target temperature, and it will pulse the pump to maintain it, acting like a modern, variable thermostat. It also manages your electric fans and performs the critical post-shutdown run-on to prevent heat soak. For a plug-and-play solution that just works, this is the one.

Meziere WP136S: Unmatched Long-Term Durability

When your travels take you thousands of miles from the nearest auto parts store, absolute dependability becomes the top priority. This is where Meziere shines. Machined from billet aluminum and built with a heavy-duty motor designed for 50,000+ hours of continuous use, the WP136S is an investment in pure, unadulterated peace of mind.

With a flow rate of 55 GPM, it can handle even the most demanding V8s and turbo-diesel applications with ease. Unlike some race-oriented pumps, Meziere pumps are specifically engineered for continuous street and heavy-duty use. The tradeoff is cost and weight; these units are significantly more expensive and heavier than their plastic-bodied counterparts. But if you’re building a "forever rig" and want to install a cooling component you’ll never have to think about again, Meziere is the name to trust.

Bosch PAD 12V Pump: A Reliable OEM-Grade Choice

Not every conversion needs a firehose of a water pump. For smaller engines, or for auxiliary circuits like a liquid-to-air intercooler or a cabin heater loop, the Bosch PAD pump is an unsung hero. This is an OEM-grade unit used by major car manufacturers, which means it has been tested to an extreme standard of reliability and quiet operation.

Don’t be fooled by its small size or low price. This pump is a workhorse, designed to run for thousands of hours without a hiccup. Its flow rate is much lower—typically around 5 GPM—so it’s not suitable as a primary pump for a large engine. However, for a 4-cylinder diesel swap in a small van or as a booster pump in a long coolant line, its efficiency and bulletproof nature are exactly what you need. It’s a perfect example of matching the right tool to the right job.

Pierburg CWA400: High-Flow German Engineering

For those who want cutting-edge performance and are comfortable with a bit more complexity, the Pierburg CWA series is a game-changer. These pumps are often found in modern high-performance vehicles from brands like BMW and Mercedes-Benz. The CWA400, in particular, offers an incredible flow rate—often exceeding 60 GPM—from a very compact and efficient brushless motor.

The key thing to understand about the Pierburg is that it’s a "smart" device. It doesn’t just turn on with 12V power; it requires a specific PWM (Pulse Width Modulation) signal to control its speed. This means you’ll need a dedicated controller to run it. While this adds a layer of electronic integration, it provides unparalleled control over your cooling system. For tech-savvy builders with big power and big cooling needs, the CWA400 delivers OEM levels of performance and efficiency.

PRP 600 Series: Billet-Proof Cooling Power

Hailing from the world of high-performance racing, parts from companies like Peterson Fluid Systems (PRP) are built with one thing in mind: surviving extreme abuse. The PRP 600 Series pumps are machined from billet aluminum and feature a rugged, inline design that’s both strong and easy to package in a tight engine bay.

While their roots are in racing, their durability translates perfectly to the demands of a heavy RV. A pump that can keep a 1,000-horsepower drag car cool between rounds will have no problem managing a loaded-down van on a 6% grade. They offer flow rates in the 50-55 GPM range, putting them in direct competition with Meziere. The choice often comes down to brand preference and specific fitment needs, but either way, you’re getting a component built to last.

EMP Stewart Pro: Maximum Flow for Demanding Rigs

Sometimes, you just need overwhelming cooling force. For massive diesel pusher conversions, big-block V8s in Class A motorhomes, or highly tuned engines generating immense heat, the standard options might not be enough. This is where commercial-grade hardware like the EMP Stewart Pro pump comes in.

These pumps are designed for city buses, heavy machinery, and military vehicles. With flow rates that can push past 100 GPM, they move a staggering amount of water. They are built for extreme duty cycles and feature brushless motors and intelligent controllers for maximum reliability. This is, without a doubt, overkill for 99% of conversions. But for that 1% with truly massive cooling requirements, the EMP Stewart is the ultimate solution, providing commercial-level performance for the most demanding rigs on the road.

Matching Pump Flow Rate to Your Engine’s Needs

The biggest misconception is that more flow is always better. That’s not true. Coolant needs a certain amount of "dwell time" in the radiator to effectively transfer its heat to the air. Pushing it through too quickly can actually reduce cooling efficiency. The goal is to find the right balance for your specific setup.

Here’s a practical framework for choosing a flow rate:

• Small to Medium Engines (4/6-cylinders, small V8s): A pump in the 25-40 GPM range is your sweet spot. The Davies Craig EWP150 is a perfect primary pump here.
• Large Engines (Large V8s, most turbo-diesels): Look for a pump in the 40-55 GPM range. This is where the Meziere and PRP pumps excel, providing enough flow for heavy loads without being excessive.
• Extreme Applications (Big-blocks, high-performance diesels): If your engine is a true monster, you’ll want 55+ GPM. The Pierburg CWA400 and EMP Stewart pumps are designed for this level of demand.

Remember, the pump is only one part of the system. Its performance is directly affected by your radiator’s size and efficiency, the quality of your cooling fans, and the diameter of your hoses. A great pump can’t fix a poorly designed system. You have to look at the entire cooling circuit as a single, integrated unit to achieve true temperature stability on the road.

Ultimately, upgrading to an electric water pump is about gaining control. It allows you to give your engine the cooling it needs, when it needs it, regardless of what your right foot is doing. It’s one of the most effective reliability upgrades you can make, ensuring your custom-built home on wheels keeps you moving toward the next adventure, not waiting on the side of the road.