Motorhome or tow vehicle, your motorized equipment needs to keep its cool to be efficient, and to avoid costly break downs. Overtaxed cooling systems can actually cause fires that can burn up your motorhome faster than you can grab the dog and the wife and head out the door. But caring for your RV’s cooling system isn’t difficult.

Automotive professionals warn that each power train has it’s “happiest” operating range, and engineers design cooling systems around those specific needs. But as technology has “advanced,” those “happy operating ranges” have gotten tighter and tighter–and industry insiders warn they may just get tighter. Hence, the need for staying on top of cooling system maintenance.

Here’s a few things to look for:

Hoses: All radiator hoses will 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 could 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 have warned us 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.

Drive belts: Get old, cranky, and slippery. Look at them closely–both sides by twisting them–look for signs of 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 an overheat or other problems. Push down on the belt at a point midway between pulleys. If it depresses more than one-half to three-quarters of an inch, it could be too loose. However, an overtightened alternator belt can damage bearings, so use a belt tension gauge if in doubt.

System pressure cap: Yeah, we used to call them “radiator caps,” but you may even find them on the coolant reservoir these days (see photo). A system 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.

Fan blades and clutch: Loose rivets, bent blades, or cracked blades, all of these 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 1/4 inch, the clutch bearing is on the way out.

Water pump: You don’t want a water pump to give up the ghost while heading down the American 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 loose 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: Change your coolant at recommended intervals, and always use the specified coolant. Many diesel engines need a regular check for SCA (supplemental coolant additive). 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, so 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.

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 harms 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 overheats. 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.

Under new federal regulations, 2010 diesel engines will have more stringent emissions standards. RVers who buy new trucks or motorhomes equipped with “oil-burners” will find they’ll have new things to think about–and in many cases, more stuff to buy.

The new regulations mandate that diesel engines cut out 90% of the currently allowed emissions of nitrogen oxide, a contributor to acid rain, global warming, and respiratory problems. Engine manufacturers have taken two different routes to the solution: One is through redesign of exhaust gas recirculation systems, the other is through a process called selective catalytic reduction (SCR). GM, Ford, and Dodge say they’ll all be using SCR in their 2010 diesel trucks.

For SCR equipped owners, this means a bit more work, and expense. The devil is in the details of just how the system works. In the typical Cummins system, Imagine your diesel’s exhaust, having just passed out of the exhaust manifold. It travels down the pipe and heads into a particulate filter that snags many of the nasty little particles associated with respiratory problems. Next it travels into a new device called a decomposition reactor. This reactor allows a fine spray of liquid called DEF (diesel exhaust fluid) to mix into the exhaust stream. The cooled and moisture enriched exhaust then streams into an SCR catalyst.

What’s this DEF? Ah, nothing more than a mixture of about two-thirds deionized water, and two-thirds purified urea. And what’s urea–if you’re thinking urine–you’re in the right track. Urea in a natural state is a waste byproduct, but happily, it can be produced synthetically and odorlessly. As this urea containing DEF is shot into diesel exhaust, it is changed in the decomposition reactor into ammonia, mixing with the exhaust’s nitrogen oxide. Once pumped on into the catalytic converter, the rich-in-ammonia nitrogen oxide is converted into nitrogen gas and water vapor, which make their way out of the exhaust system. Both nitrogen gas and water vapor are environmentally friendly characters.

So what about this extra work and cost we talked about? The DEF, the liquid that mixes with exhaust, has got to come from somewhere: A reserve tank on board your vehicle. This means you as owner/maintainer, will periodically have to “top off” your DEF tank. How often? Industry whiz kids say you’ll burn about one and a half to two gallons of DEF for every 100 gallons of diesel you burn. And the cost of the DEF? That’s a football being kicked around right now, and perhaps about as predictable as the outcome of the SuperBowl. Engine maker Navistar says they think it could cost as much as $35 a gallon.  For big truck users–that is big as in 18-wheelers–there may be a helper here: Big trucks could see a slight increase in fuel economy. But for the rest of us, just look for greater costs–the fuel economy probably won’t translate down to us. Navistar’s estimate may be on the high side, as another outfit says they see DEF selling for as little as $2 a gallon in bulk.

So, how about just not putting the DEF in the reservoir and saving the cash? The truck manufacturers have got you figured out. You may see a dash warning light nagging that you’re getting low on DEF. Ignore it, and your rig could go into “limp” mode, reducing available speed and horsepower. Or you might find you just can’t start up again after you stop. In any event, you won’t be “getting away with it,” by skimping on DEF.

And one more nagging issue: While truck manufacturers should be working on a system to keep the DEF reservoir warm–the stuff gels at 12 degrees farenheit, storage for desert dwellers could become a problem. Above 80 degrees, DEF begins to degrade in quality, and storage in a hot climate could become an issue.

Stick around, we’ll update you on the DEF/SCR issues as they develop.

photo: US E.P.A.

Perhaps one of the most frustrating of repair issues for RVers is when encountering a stuck screw. Since RVs are often held together with plenty of them, the chances of running into some of these recalcitrant fasteners is pretty high.

First though, be aware that not every screw you may encounter in your RV maintenance may be the common Phillips style. There is, of course the common straight slot–sometimes holding cabinet hardware in place. But another screw type you may run into includes the clutch head, or as a contractor buddy of ours calls them, “bowtie screws.” Quite common in the mobile home industry, clutch screws require a special bit or driver to operate; they’ve migrated over into some parts of the RV industry.

For the sake of our friends who are new to do-it-yourselfing, a Phillips head screws look like a cross with equal leg lengths, coupled with a slight rounded area at the cross piece. There are three common sizes of Phillips head screws, #1, #2, and #3, ranging from small to large, in that order. Use the wrong sized screwdriver on a Phillips and you can be sure to damage the screw head. You’ll learn to recognize which is which, but simply put, the driver head should fit snugly into the screw slots, and not “give” when turning.

There are a number of approaches to take in getting stiff-necked screws to move on out. First, if the screw is swathed in paint, give the screw a good whack with a hammer to loosen the paint before applying the screwdriver. If the slots are overrun with paint, use a utility knife to carefully remove the paint, giving the driver head plenty of access.

When using a cordless drill as a power driver for screws, be sure not to set the drill’s clutch at too high a setting. If the screw initially resists your loving labors, reduce the clutch setting and allow the drill to “hammer” the screw. This non-turning but still tapping on the part of the drill may help to loosen the screw, then by slowly increasing the torque on the screw by increasing the pressure applied by the clutch, good things sometimes happen.

If your driver can get a good bite, don’t just turn the screw counter-clockwise to remove it, work it both ways. Sometimes the tighten-loosen approach will help break a tight screw loose. If the screw is tight in wood, pull out your soldering iron and heat the screw head up with the iron. Work carefully so as to not damage the material! You can allow the screw to cool before taking after it with the screwdriver.

For screws in metal, heating may assist. If it looks as though corrosion might be a factor, giving a shot of penetrating oil (Liquid Wrench or similar) and allowing some time for the juice to penetrate can help. If you’re in a fix and don’t have any penetrating oil on hand, check out some other alternatives: Lemon juice, hydrogen peroxide, cola, even hot sauce!

If the head is so damaged that the appropriate driver will no longer work, we’ve had a lot of success with a screw extractor sold under the name of the Grabit Pro. Sized to fit the screw, the extractor fits in your cordless drill. One end “burnishes” and prepares the screw, the other end does the actual extraction. We’ve yanked some pretty nasty screws with this device.

Again, before you start, make sure you’re using the correct sized tool for the screw. Don’t apply too much pressure at once, and if push-comes-to-shove, turn on the Torquemada on those twisty fasteners.