Our $25 Radiator Spray Setup

During our first outing in July 2021 just east of Albuquerque, New Mexico, we faced a daunting long, hot, and steep climb. The temperature outside was well above 100°F, which caused our bus's coolant temperature to rise from the usual range of 160-180°F to over 195. To avoid any potential engine damage, we decided to take a break at the next rest stop. We turned off the engine and spent nearly 30 minutes there, allowing ourselves time to use the restroom and grab a quick snack. Upon our return, we noticed that the coolant temperature had dropped to the low 170s, and we continued our journey.

During our last trip back home in May 2022, we were driving down from the mountains of Payson, Arizona toward Gilbert. This route is mostly a downhill descent, but there are a few areas where it becomes a steep climb again. The outside temperature was scorching, well over 100°F, and our little bus had to climb the steep grade. Consequently, the engine temperature began to rise, reaching almost 195°F. We kept a watchful eye on it throughout the ascent, but we wished we had a way to cool it down.

We had gone through countless hills without any issues before, but the temperatures in the southwest are much hotter than what we saw traveling back east. We experienced those two instances where the temperature got to the point where we started to feel uncomfortable. Although I have seen some people take their Detroit Diesel 8v71 a little higher, 200°F is my personal comfort zone. To be fair, we've never seen our engine reach that temperature, but it's gotten close enough that we thought adding a sprayer would be a good idea.

When we purchased our bus, we discovered that it came equipped with a radiator spray feature installed by the previous owner. The switchboard next to the driver had a broken toggle switch labeled for a radiator spray, as well as an old and damaged pump in the rear of the bus. The switch's wire was not connected to anything, and the pump had no water or electrical connections. Clearly, at some point, the previous owner had a sprayer for the radiator but then later dismantled the system. During our switch plate redesign, we kept the water spray toggle but did not connect it to anything, leaving it as an option for future installation. However, after experiencing coolant temperatures reaching 195°F, we decided to revisit this.

Our goal for this project was to find a simple spray solution as an insurance policy. The first step was choosing a kit. We already had the switch set up and wired in, so we just needed a way to get the water to spray on the radiator. We considered purchasing a universal windshield washer pump bottle kit for about $20 on Amazon. There were several problems with this approach. First, the tanks on those are pretty small (typically 1 liter), so we would have to remember to keep that little tank filled up. In addition, the 12V pumps on those are usually pretty weak and not designed for as many nozzles as we needed. What seemed more appealing to us is those misting systems that are used at restaurants and in backyards. Those provide much finer atomization of the water and should lead to better, faster cooling. The very best of those systems utilize a very high-pressure pump (some run at 1000 psi!) and have all kinds of filters and systems to keep them operating smoothly even with hard water. These systems can easily cost a few thousand dollars. We were not interested in something that fancy. Instead, we opted to go with a 16-nozzle kit that hooked up to a garden hose and sold on Amazon for $18. We were pretty sure our RV water pump could run it, and we already have a garden hose nozzle in the water bay.

After deciding on the kit, we just needed a way to turn it off and on. Since the misting kit we chose used 1/4" tubing, we opted for a 12V solenoid valve with 1/4" quick-connect fittings.

After receiving the parts we ordered from Amazon, we decided to test out our setup. Our first concern was whether there would be enough pressure for the misting system to atomize the water properly. Our second concern was whether the 12V solenoid valve would allow enough water flow for the system to work effectively. We began by testing with a single nozzle but we were disappointed with the amount of water produced. However, upon testing the full 16 nozzles, we were pleased with the results. Once we added the solenoid valve, we were relieved to find that it worked perfectly.

All that was left to do was secure the lines and get everything wired up. We got this project done quickly in May 2022, and when we got back on the road a few weeks later, we had a great chance to test the system on a long climb in hot temperatures.

We left for a trip in June 2022 that would take us north through Flagstaff, AZ with a big climb in some really hot temperatures. As we started at the base of the mountains, our engine was already at about 185°F and we had a good 7000 ft climb to go. We switched the water misters on, and to our delight our engine maintained the 185°F temperature all the way up the climb.

Luckily, we do not need to use the system often, but we have used it a few times since then as we have traveled through the southwest desert and Rocky Mountains. With Phoenix, Arizona as our home base, we come back often with mountains to climb and often hot temperatures. We are glad to have this radiator spray installed to give us peace of mind as we try to keep this old engine rattling down the open road.

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