With the hot weather approaching, now is the time to review your department`s warm weather operational procedures. There are not many areas in this country in which a fire department would not operate in warm weather. Even if you operate in an area where the temperature never gets above 607F, mechanical failures and human error occur and engines, transmissions, and water pumps overheat. A review of driver-operator techniques and special maintenance during hot weather may prove to be invaluable and keep apparatus from failing during an emergency.

During extreme heat, most fire departments adopt guidelines for firefighting personnel such as lightweight duty wear, limited nonessential physical duties, and quicker relief for working personnel at fire scenes. Air-conditioning is even being installed in new apparatus for firefighter health and rehab. Most times what is overlooked during extreme heat conditions is the special needs of the apparatus and the essential driver-operator knowledge of those needs.


The driver-operator`s duties must start in the morning with the morning apparatus checkout. The following are items (along with some dos and don`ts), that, at a minimum, should be included in your morning apparatus checkout.

Check the coolant level by the sight glass or by the level in the reservoir. Do not assume the last driver did it–the motor`s life and your next promotion could depend on that coolant check. Do not depend on the low coolant warnings installed on most new apparatus, either. They sometimes are too low in the radiator and do not always register. When removing the radiator cap to check the fluid level, inspect the gaskets on the cap and make sure to reinstall the cap properly. (Be sure that the radiator is cool before attempting to remove the cap.) Numerous apparatus have been declared dead because of a blown-off or lost radiator cap! Try ex-plaining that one to the fire chief and the mayor!

Check the front side of the radiator for debris such as leaves, pine needles, mud, and dirt. If air cannot get through the radiator fins, the coolant cannot cool the motor. Apparatus with center-mounted radiators suck the air from the road. This problem is commonly overlooked.

Check the fan belts (if so equipped). Check for tightness, wear, and cracks.

Check hoses and the radiator for leaks. Visually check the hoses and the radiator for signs of leakage. Coolant that is leaking or seeping over time will evaporate and leave a residue. Always look for puddles on the floor. If you find any unusual puddles, whether they be coolant, oil, or any other fluid, report it immediately to maintenance.

Check auxiliary cooler valve. Check to make sure it operates freely, and leave it in the closed position until it is needed.

Check both engine temperature gauges. There is one gauge on the panel and one gauge on the dashboard. Watch the gauges during startup and warmup, making sure that the motor warms up at the normal quickness to operating temperature (1807F) and then maintains that temperature. Compare the gauges against each other to make sure they are within 10 percent of each other.

Check motor oil and transmission oil levels. One of the jobs of the oil is to cool, so keep the oil levels to the full line.


Unlike the over-the-road truckers whose vehicles overheat while in city traffic or pulling long grades, the driver-operator will most likely experience overheating problems while pumping. Diesel fire apparatus have a motor designed to operate at 1807F. If the fire apparatus is designed properly, this motor should never run much above 1807F. National Fire Protection Association standards require that fire apparatus perform at full pump capacity with all accessories operating (including the A/C and all emergency lights); the engine cooler off; and all engine hoods, covers, and doors closed without overheating

Remember, the key is that normal motor operating temperature is 1807F. The motor (and all its components), oil, and diesel fuel are all designed to run at 1807F. This is where the horsepower curve is rated, where torque is measured, and where the least bearing and piston wear occurs. It is also the world in which a diesel motor wants and needs to live.

Because of its design, a diesel motor will also lose power operating with an ambient (outside) air temperature of 907F or higher. At this temperature, the diesel motor has to work even harder to perform the same, and the demands on the cooling system are even greater.

When the temperatures reach the coolant`s boiling point, all cooling ability completely disappears. Remember, there are no automatic shutdowns on fire apparatus: The motor remains running for firefighter safety at the expense of the motor. However, with the proper coolant mixture, the boiling point is increased to approximately 2307F, a point in favor of the motor. A pressurized system will also slightly raise the boiling point.

The motor cooler mounted on the panel is a very misunderstood component. By leaving the motor cooler on at all times, or by turning the motor cooler on before the operating temperature is reached, a delay or even motor damage (a result of improper engine warmup) may occur. Turn on the motor cooler only after the motor reaches 1807F, and make sure that the motor does not overcool.

During hot weather pumping operations, turn off all unnecessary accessories such as the A/C, emergency lights, and headlights. The alternator will now use less horsepower, thus generating less heat by the motor. Running at higher RPM will help cool the motor. This can be accomplished by increasing RPMs and controlling hose discharge pressures by gating and feathering rather than using the throttle. With two-stage pumps, if circumstances permit, run in the volume mode instead of pressure. The motor will run at a higher RPM and will use less horsepower to move the same amount of water. Depending on the design of the apparatus, opening engine compartments or the hood may help.

The pump also needs the same special care. Keep the water flowing–never let it churn inside the pump. During overhaul operations, when less water is flowing, let the water recirculate, overflow the tank, dump it on the ground, or do anything else it takes to keep the pump cool. Yes, the old teachings of feeling the temperature of the streamer port is a good indication of pump temperature. Today, however, there is an option to install a pump temperature warning device. If your apparatus has one, learn how to use and test it.

Cavitation happens at higher water temperature. The magic number for incoming water temperature is 607F. Theory says that the water will easily cavitate at 607F or above when combined with the high pump temperatures. Keeping adequate incoming residual pressures is even more important in hot weather.

Drafting with warm water can pose real problems, especially if a high “pull” is needed. If you have the choice between warm pond water and cool lake water, opt for the cool lake water. When drafting, always keep the water flowing, and recirculate the water back to the lake constantly so that when the lines are shut down the draft is not lost. With warm water and a warmer pump, the prime is easily lost. Sometimes getting a prime back into a hot pump is impossible.

Summer sometimes brings low hydrant pressure, which can plague operations. The ability to check residual pressure and flow drop and figure estimated water is essential knowledge for the driver-operator. If the hydrant cannot flow the water needed for the situation, the driver-operator has to quickly relay that information to the water supply officer so more water can be obtained from elsewhere. Sharpen these skills for the summer; it may save a life or property.

While driving the apparatus, watch motor temperatures in heavy traffic or when pulling a long grade. The use of transmission retarders can quickly heat up transmission fluid. The driver-operator dash has a transmission temperature gauge for just this reason. The transmission will start overheating at 3307F and self-destruct at 3607F. Brake pads and shoes heat up quicker and stay hot longer. The driver-operator should know the apparatus` limitations and drive accordingly.


Consider the following scenario: A motor failed during a pumping operation. The mechanic examines the motor and declares it “junk.” The motor now has to be replaced. More often than not, one error has caused the problem. Consider the following common errors:

The overheating could have been prevented by the springtime tuneup (discussed below). Adding chemical additives in the coolant may have avoided the breakdown.

The driver-operator was not watching the gauges and did not notice the motor overheating.

The driver-operator never notified the incident commander that the apparatus was having a problem. If the IC had known of the problem and if the pumper had been shut down, maybe another pumper could have taken its place.

As the engine started to overheat, and if the driver-operator had the knowledge, the motor temperature may have been able to be controlled by proper use of the pump cooler and/or fast idle, turning off the A/C, or opening the engine hood.

Automatic motor shutdowns are not allowed on emergency equipment.

Warning lights and buzzers may have malfunctioned or had gone on too late to avoid motor damage.

Budget restraints may have prevented proper apparatus maintenance.

Age, excessive hours, “it`s worn out,” and “it was due” are among the favored explanations!

The driver-operator has no control over motor defects such as blown gaskets or a water pump other than to shut down the motor to avoid more damage.

We can blame motor failure on two or more of the following: driver-operator error, improper maintenance, the budget, apparatus age, and mechanical failure.

Failure of the apparatus causes a mountain of problems, especially with the smaller departments. Firefighter safety may have been compromised when the breakdown occurred. Was the public life and property endangered when the breakdown occurred? The chief has to explain the situation to the mayor. Not only does the breakdown cost unbudgeted money, but now the apparatus is out-of-service for an indefinite period of time for repair, rebuilding, or replacement.

It is possible that a springtime tuneup (discussed below) might have helped prevent the problem. If you find a problem, do not fall into the budget restraint trap. For example, radiator repair or replacement may cost well over $1,000. The budget is sometimes used to delay repairing the apparatus. That $1,000 cost may have sounded expensive before the breakdown, but now, after the catastrophic failure, it would most certainly have been cheaper!


It is now time for the springtime tuneup. This is a preventive plus in your maintenance program. “Pay me now or pay me more later” is a most appropriate expression to better describe the advantages of a springtime tuneup. I have compiled a partial list of the items that should be checked before the hot weather arrives. Some of these items, however, should be checked regularly.

Coolant: Coolant must be flushed and replaced every two years. Proper coolant must be used at a mixture of 50-50. Do not forget to flush and clean out (or purge) the reservoir bottle. When flushing, check the low coolant sensor operation when coolant is drained below the sensor. Diesel motors require the addition of a chemical additive supplement (that includes nitrates and pH control). The supplement must be controlled at the required percentage. Coolant test kits are available to check these percentages. Internal motor damage will occur without the correct coolant, water, and chemical mixture. Visually inspect the coolant for any sign of oil. Small amounts of oil in the coolant will cause overheating. (Oil in the coolant might indicate a defective transmission or oil cooler.) If there is any suspicion of oil in the coolant, take a sample and send it in for an analysis. Most dealerships can do this for you.

Radiator: Visually check the radiator. Make sure the coolant sight glass is in good shape and the coolant can be easily seen. Look for obstructions to the air flow. Fins can get clogged with dirt, leaves, pine needles, oil, and grease. Clean the fins by soaking them in a cleaning solution and then rinsing with the garden hose. Look for fin deterioration. Fins have to be solid to transfer heat. Fins deteriorate from chemicals such as salt and sea water. Look for signs of leakage along seams, inlet and outlet fittings, and tubes. Inspect the tanks, tubes, header seams, and brackets to be sure they are straight and square. Any bent, bowed, or bulging areas of the radiator indicate prior extreme pressures or fatigue; repair or replace the radiator immediately. Check for a clogged radiator by using a heat sensor gun–the same one you use to check for heat behind the walls. The part of the radiator that is clogged or restricted will be cooler than the rest of the radiator. If you think you have found a problem, have a radiator specialist check it out.

Hoses and clamps: Check for leakage or seepage, cuts, and rubbing. Check for flexibility. The hoses need to be flexible enough for motor vibration. Replace the hoses that are too stiff. Hoses that are too soft may indicate oil in the coolant. Check all clamps for tightness–rusty clamps may break. Replace them with stainless steel clamps.

Pressure test coolant system: Make sure the coolant system holds pressure. Make sure to test the system at the manufacturer`s recommended operating pressure. Also test the radiator cap at the same pressure. Visually check the cap for gaskets and vacuum relief valve and spring.

Coolant fan: Clean all oil, grease, and dirt from the fan blades so they will move air more easily. Check to make sure the fan clutch (if so equipped) engages when the cooling system attains operation temperature. Some fan clutches have an oil sump; fill with correct oil.

Fan shroud: Check for mounting and damage of the shroud and shields. Make sure that the air cannot recirculate around the shroud and back into the radiator.

Heat shields: Remove the pump heat shields that trap hot air from the muffler if so equipped.

Thermostat(s): Check the thermostat(s) by using a heat sensor gun (if available) or temperature probe. Check at the thermostat housing(s) outlet to see at what temperature the thermostat opens.

Heater control valves: Now is a good time to check the valves that open and close the coolant flow through the heater hoses. Stuck or open valve(s) will cause cab heaters to keep working, which will cause an A/C unit not to work and sweaty and upset firefighters.

Air-conditioning: Have annual basic refrigerant service. Check all the belts. Clean fins in the evaporators and condensers. Check and clean the condenser fans. An A/C system that is properly serviced will run with lower compressor head pressure, which saves horsepower and heat.

Motor oil: Make sure oil changes are up-to-date. Make sure you use the right grade (SAE) oil conducive to the local weather conditions. Make sure to use the proper API rating. For example, an API rating of CG is for diesels, and an API rating of SJ is for gasoline engines. Some engine manufacturers do not recommend oils that have combined ratings for both gas and diesels such as an SJ/CG oil. Check the operator`s manual for the correct oil. If motor oil fails, it usually happens in hot weather. Make sure you use the right oil.

Automatic transmission fluid: Change the transmission fluid annually. This would be the right time to do just that. Drain the fluid at the drain plug, and change the external filter (if equipped). Change the internal filter pursuant to the owner`s manual recommendations.

Good luck with your warm weather operations. Your department probably has some tricks of its own to deal with such operations. Make sure you pass these tips along. By performing a little extra maintenance and conducting warm weather driver-operator training, maybe you can keep your “cool” this summer. n

TERRY ECKERT, a 15-year veteran of the fire service, is a firefighter and head of apparatus maintenance in the Darien-Woodridge (IL) Fire District and the chief engineer of the Westmont (IL) Fire Department. He has 25 years of experience as a vehicle technician. He is an ASE-certified master automobile technician, a master heavy truck technician, and an EVT Level 3 master technician. He also has ASE certification in advanced level engine performance. Eckert is a member of numerous professional associations, including the National Association of Emergency Vehicle Technicians (NAEVT) and the Illinois Fire Apparatus Mechanics Association. He is a member of the EVT Certification Commission, where he serves on the Validation Committee and had chaired the E-3 section, and the NFPA Technical Committee on Emergency Vehicle Technician Professional Qualifications. He was the 1997 recipient of the NAEVT Certificate of Achievement Award.

(Top) Check and observe the temperature gauge on the pump panel. (Photos by author.) (Bottom) Also check the temperature gauge on the dashboard, and compare it with the gauge on the pump panel. Make sure they are within 10 percent of each other.

The driver-operator dash has a transmission temperature gauge. The transmission will start overheating at 3307F and self-destruct at 3607F.

There is an option to install a pump temperature warning device.

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