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8 steps for keeping your fire apparatus cool this summer

Master mechanics and emergency vehicle technicians recommend the following apparatus maintenance tips to keep trucks on the road in soaring temperatures


Following these eight steps can go a long way to ensuring that your fire apparatus can meet the operating challenges of hot summer weather.


Keeping your fire apparatus maintained in good working condition is important year-round, but summer heat can present extra challenges for your truck’s engine cooling system, as well as other less obvious mechanical systems.

As summer temperatures rise into the triple digits, don’t leave yourself and your truck steaming!

Here are eight steps for your department’s personnel that can keep your fire apparatus operating properly in summer’s heat.

1. Know if your fire truck model is prone to overheating

Many heavy trucks – and that’s what your fire truck is – overheat more than other similar models. This tip is important because it highlights the need to be extra-vigilant.

If you suspect your model of truck is prone to overheating, the first thing you should do is call your dealership to see if there are any outstanding warranties or service bulletins on your truck. This one action on your part may identify if there’s a known flaw, like a poorly designed head gasket, that’s causing the problem.

2. Train your firefighters to pay attention to their gauges

Seems like rather elementary advice, no? But realistically, too few drivers – especially younger drivers who don’t have experience operating any vehicle bigger than a car or light truck – make a habit of monitoring their truck’s engine gauges, especially the temperature gauge.

Aside from the temperature gauge, the engine oil pressure reading, battery charge indicator and the boost and vacuum gauges (if your truck has a turbocharged engine) are also important for monitoring your truck’s performance during hot weather.

Make sure your operators know what the normal operating temperature for their truck’s engine is. They should learn to note what the temperature gauge is showing on several different occasions after the truck’s engine has had a chance to run for a while. The engine operating temperature should remain stable, or consistently fall within a certain range, if the truck’s engine cooling system is operating properly.

When those temperature readings begin to increase rapidly, you may have a problem. That’s the time to have the engine cooling system evaluated by your department’s maintenance folks. Early intervention can be the key factor in avoiding a catastrophic engine failure.

3. Look for obvious leaks in the firehouse bays

Engine coolant fluid, oil, transmission fluid, brake fluid and transfer case fluid are meant to stay sealed inside your engine until their intentionally drained and replaced. Finding fluid beneath your parked fire apparatus is never a good sign. When your operators find fluid under their vehicle, it should serve as a red flag that requires further investigation on their part to identify the leak.

In the past, an engine coolant leak could easily be identified as most vehicles used a similar engine coolant fluid that was bright green in color and had a sticky/sweet smell. Today’s engine coolant fluids for heavy trucks come in a variety of colors including red, orange and even pink. Your vehicle operators need to be familiar with the fluids used in their truck so they know what to look for.


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4. Look under the fire apparatus hood

Don’t wait for a red flag before checking your truck’s cooling system. Open the engine compartment and give the engine’s coolant reservoir level a look. If the level falls below the minimum line, don’t ignore it or just add coolant to the tank and forget it. Something’s wrong.

It’s normal for a little bit of fluid to boil away or evaporate – but just a little. You’re probably looking at a small leak that’s not big enough to leave telltale stains, drips or fluid under the truck.

During that under-the-hood inspection, check the hoses and lines of the engine coolant system for any signs of leakage (e.g., staining on engine parts). Then, refill the reservoir to its proper level with the appropriate coolant fluid mix and check back frequently to ensure the level is staying consistent.

5. Avoid a busted hose or belt

Checking hoses and belts is a maintenance step that’s frequently overlooked or forgotten, despite its simplicity. The belts and hoses are still made of rubber, which can crack, fray, leak or rot. Check the edges of the belts for fraying or wear as well as proper belt tension.

Don’t just look at cooling system belts. Improper belt tension on the truck’s alternator can make it work much harder than necessary to transfer power (unsuccessfully) to other truck systems. The alternator runs more to get the job done and all that wasted effort (and extra friction) creates extra heat within the engine compartment. This, in turn, raises the overall temperature in the engine compartment.

As the engine overheats, pressure builds in the cooling system, putting additional pressure on the hoses. And we all know what becomes more likely then, right?

“With the engine tunnels being wrapped with insulation, there is nowhere for the heat from these newer engines to go,” said Brian Toth, a master mechanic with the North Shore Fire Department in Glendale, Wisconsin. He added, “I have replaced countless radiator caps during [preventative maintenance] because they won’t hold pressure.”

Dan Flanagan, an emergency vehicle technician with the Simsbury Fire (Connecticut) District, recommends checking the radiator pressure cap with a tester to ensure it reaches the proper pressure. “Since the boiling point of the coolant mixture is increased by around 3 degrees for every PSI of pressure, this is very important in the summer,” he noted.


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6. Use the proper coolant-to-water mixture

Every truck’s cooling system requires a mixture of coolant and water consistent with the manufacturer’s recommendations. Non-compliance with the manufacturer’s suggested ratio, by adding only water or only coolant puts your truck’s engine (and possibly its warranty) at risk. The proper coolant-to-water mixture can make a big difference. Look at these two scenarios:

  • A coolant mixture of 60% water and 40% coolant can provide boil-over protection up to 259 degrees F (126 degrees C) and freeze-up protection down to minus 10 degrees F (minus 23 degrees C).
  • A coolant mixture of 30% water and 70% coolant can provide boil-over protection up to 270 degrees F (132 degrees C) and freeze-up protection down to minus 62 degrees (minus 52 degrees C).

7. Don’t overload your fire apparatus

Many fire departments struggle to keep from overloading the gross vehicle weight rating of their fire apparatus.

When overloaded, every part of the fire truck’s powertrain (including the engine) must work significantly harder to get all that extra weight rolling down the road – and keep it in motion, too. This extra work means extra heat generated by the truck’s engine. If the cooling system can’t keep up with the demand – you guessed it – potential severe engine damage.

Know the GVWR for all your department’s fire apparatus and ensure that each vehicle’s weight is maintained within that rating. The GVWR can be found in the owner’s manual or on a decal or plate located on the inside edge of your truck’s door frame.

A simple strategy to avoid overloading your truck – and overheating your engine in the process – is to have each of your department’s trucks weighed twice a year (spring and fall). The Chesterfield County (Virginia) Fire and EMS Department (where I began my career) does this by taking its fire apparatus to one of the County’s two landfill sites and using the truck scales the staff use to weigh incoming trash trucks to determine how much they get charged based on the weight of the trash they’re bringing in.


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8. Check your fire truck’s brakes

If your truck’s engine is overheating, but you can’t trace the source of the problem to any of these pitfalls, then it may be an often overlooked area: the vehicle’s brakes. Though the engine’s cooling system and its braking system are separate, and nowhere near each other physically, dragging brakes can quickly cause a fire truck’s engine to overheat.

It’s so innocuous that a firefighter operating the truck may not even notice what’s going on, so the engine just keeps working harder as the truck unintentionally brakes itself.

That’s lots of extra heat, particularly within the engine compartment. Those dragging brakes will cause the engine temperatures to rise dramatically and very quickly, especially on extended runs.

Following these eight steps can go a long way to ensuring that your fire apparatus can meet the operating challenges of hot summer weather.

Additional resources & references

This article, originally published in July 2017, has been updated.

Battalion Chief Robert Avsec (ret.) served with the Chesterfield (Virginia) Fire & EMS Department for 26 years. He was an instructor for fire, EMS and hazardous materials courses at the local, state and federal levels, which included more than 10 years with the National Fire Academy. Chief Avsec earned his bachelor’s degree from the University of Cincinnati and his master’s degree in executive fire service leadership from Grand Canyon University. He is a 2001 graduate of the National Fire Academy’s EFO Program. Beyond his writing for and, Avsec authors the blog Talking “Shop” 4 Fire & EMS and has published his first book, “Successful Transformational Change in a Fire and EMS Department: How a Focused Team Created a Revenue Recovery Program in Six Months – From Scratch.” Connect with Avsec on LinkedIn or via email.