For RVers, this could be a long, hot summer. But getting out of the heat for many means getting away from the city and to the cool of the countryside. Nothing spoils an RV vacation faster than a breakdown on the road. One critical breakdown area can often be fixed before it ever breaks. A little advanced cooling system maintenance and repair can keep these kinds of breakdowns at bay.
You may not know it, but overtaxed cooling systems can actually cause fires that can burn up your motorhome faster than you can grab your loved ones and bail out the door. But caring for your RV’s cooling system isn’t difficult.
Automotive professionals tell us that every power train has its happiest operating range. Engineers design cooling systems around those specific needs. But as technology has “advanced,” those happy operating ranges have grown much narrower—and industry insiders warn they may get tighter still. Hence, the need for staying on top of cooling system maintenance. Here are some areas to check before you head out on the road:
Know Your Hose
All radiator hoses eventually wear out and require replacement. If a hose goes, it could cause serious problems. With the engine cool and shut down, feel along the entire surface of all cooling system hoses, including those serving the cab heater core. Hard or swollen hoses can fail at any time. Cracked or brittle hoses need replacement, too. Leaks near the terminating end of the hose could indicate a loose hose clamp—or a bum hose.
Fire department officials say that even a pinhole leak of coolant onto a hot engine part, like an exhaust manifold, can quickly evaporate cooling system water. The remaining antifreeze mixture can actually ignite—and make a motorhome go up in a puff of smoke.
Check Your Belts
Drive belts get old, cranky and slippery. Look at them closely—check both sides by twisting them—to detect cracking, a shiny “glazed” appearance, or other signs of deterioration. Replace any suspects. Loose belts do more than drop pants. In your rig they can cause overheating or other problems. Push down on the belt at a point midway between pulleys. If the belt depresses more than one-half to three-quarters of an inch, it could be too loose. Be careful though, an over-tightened alternator belt can damage bearings—a belt tension gauge can give clear direction.
Us old guys used to call them radiator caps, but you may even find “system pressure caps” in places other than on a radiator. Our coolant reservoir (overflow tank) is the only place on our tow rig’s engine where you can put coolant—no radiator cap! A cooling system kept under pressure is one that boils at a higher point, so making sure this cap is in good shape is critical. Remove the cap (ONLY FROM A COLD SYSTEM) and look at the gasket. It should be solid and supple, with no cracks or nicks that might impair its function. If you have a cap tester, use it.
Cool in a Clutch
Keeping the radiator cooled off is that all-critical fan—or even fans. Loose rivets, bent or cracked blades, all call for attention. DON’T try to straighten a bent blade, replace the fan. The hydraulic clutch on a fan “engages” the fan at a given temperature. With the engine at operating temperature but shut down, spin the fan with your finger. If it turns more than two rotations without stopping, have it checked out—it could be freewheeling when it should be engaging. Other clutch problem giveaways? A streak of dirt or oil across the clutch. These guys are filled with silicon fluid, and when the fluid leaks out, it attracts dirt. Another problem is the clutch bearing—grab the fan at opposing points and try and rock the fan/clutch assembly back and forth. If it gives more than a quarter-inch, the clutch bearing is on the way out.
The Pump’s a Prime Thing
You don’t want a water pump to give up the ghost while heading down the highway. We speak from experience. But first, don’t get taken in by unscrupulous replacers of RV water pumps. A tiny amount of coolant—even a few drops—on the outside of the water pump doesn’t mean: “Yer gonna lose that pump just around the next corner.” Nor does the old ploy of “checking the water pump for play in the bearing.” If the mechanic says he can feel that the bearing is too loose, ask him to turn your antifreeze into Jack Daniels. If he can, let him replace the water pump. Water pumps typically last many thousands of miles. If you see something like a puddle of coolant under your rig and you can’t attribute it to another source, then yep, your water pump may be about to head south.
Coolant—It’s the Water—and a LOT More
Change your coolant at recommended intervals, and always use the specified coolant. The old “green stuff” may be just what you need, but newer rigs may spec out for entirely different coolant. Drive a diesel? Many “oil burners” need a regular check for SCA (supplemental coolant additive). Why so? In a cooling system, sound vibrations can actually create tiny air bubbles. Left unchecked these little bubbles can cause “cavitation,” or a pitting of metal surfaces—like your engine block, water pump impeller blades, even the radiator. There’s a whole frightening explanation of cavitation we don’t have space to go into, but you can run an Internet search and learn more.
In any event, an SCA will smooth things out and prevent cavitation. However, SCA does deteriorate over time, so you’ll need to periodically test your coolant SCA with test strips. This is not a matter of “just dump some more in.” Too much SCA can cause problems, so TEST!
When replacing coolant according to schedule, always use distilled water or reverse osmosis processed water, NOT tap water. Even city water has nasty chemicals that can cause system clogging. And a clogged cooling system is a disaster waiting to happen. And always follow “spec” on properly draining, flushing and refilling your system. Air trapped in a cooling system can actually cause a blown head gasket or even greater mechanical disasters.
Not so Neat to Overheat
Overheating? Before jumping to unwarranted conclusions, check the simple stuff first. Look for debris like paper or leaves that may have been sucked in front of your radiator, impeding its ability to shake off heat. Check the fan clutch as we outlined. If you have electric cooling system fans, keep your fingers out of harm’s way and have someone turn on the air conditioner. If the cooling fans don’t turn on, then you may have an electrical system problem.
Obstructions in the cooling system itself can cause overheating. With a cold system, start the engine and keep your hand on the upper radiator hose. After a few minutes, the cooling system thermostat should open, and you’ll feel a sudden blast of hot water through the upper hose. If you don’t, the thermostat may well be stuck and need replacing.
Going over your RV or truck cooling system will take a little while. Setting aside a weekend afternoon will cover most troubleshooting and repair issues. But sacrificing those few hours at home are a whole lot better than how hot you’ll get under the collar if your cooling system leaves your stranded by the side of the road on an RV vacation.
Russ and Tiña De Maris are authors of RV Boondocking Basics—A Guide to Living Without Hookups, which covers a full range of dry camping topics. They also provide great resources in their book, Camp Hosting USA—Your Guide to State Park Volunteering. Visit icanrv.com for more information.Research Campgrounds, Plan RV Safe Routes & Turn your phone into an RV GPS.
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