Signs and Symptoms That Your Mid-Size Truck is Overheating

Overheating is one of the worst things that can happen to your commercial truck. If the cooling system in your medium-duty Isuzu NPR, Mitsubishi Fuso, Hino or UD Truck isn't working like it should, the engine could overheat and suffer extreme failure. We recommend you do some troubleshooting to know whether or not your engine is overheating, and what might be causing it.

Check the Engine: Start the engine on your truck and wait for it to heat up. When the needle on the temperature gauge sits at or near the middle mark, your engine is sufficiently warm. If it rises above the center mark on the gauge, your engine is starting to overheat.

Check the exhaust. If there is steam coming out of the tailpipe, then your head gasket has failed, and this is likely causing your engine to overheat due to engine coolant leaking into the combustion chambers instead of cooling the engine.

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Signs & Symptoms:
The coolant level is low. In hot weather, the coolant in your engine can get low by evaporating through the overflow reservoir. As hot coolant is pushed into the reservoir, a certain amount of steam is produced. Over a long time, this can lead to lowering coolant levels in the system. It may also be that the system was not filled properly after the last cooling system repair or maintenance. This is easy to diagnose. Remove the radiator cap when the car is cool and look at the fluid level. If the reservoir tank fluid level is at or below the lower mark on the reservoir tank, fill your reservoir tank with a mixture of 50/50 engine coolant and water.

You have a leak in the engine cooling system. Leaks can occur in a cooling system several ways. The radiator or heater cores can become old and develop pin holes that leak coolant under pressure. Likewise, radiator and heater hoses become weakened by the high pressure that they sustain until the hose ruptures and leaks coolant. Just before the water pump fails, it will often leak cooling fluid from the weep hole on the bottom of the pump. There are also a few places around the engine where gaskets can leak coolant. These leaks are usually either diagnosed immediately when the hood is raised while the car is hot, or antifreeze will be found on the ground under the car when it is parked.

The water pump is failing. If the water pump isn't circulating the coolant, your car will overheat. Most water pumps that are failing will give a high pitched squeeking sound that is hard to miss. When you start to hear the squeek, you will only have a few days to fix the problem or risk being stranded. Or the water pump may start to leak fluid from the weep hole at the bottom of the pump. This is a sign that the internal seal is failing. When this sign shows up, get the car fixed quickly because it will continue to get worse.

The thermostat is bad. Most of the time when thermostats fail, they fail to open. This means that the thermostat acts like a plug in the cooling system and keeps the antifreeze from circulating through the radiator to cool down. The result is that the vehicle overheats. When there are no system leaks and the water pump is not bad, the culprit is usually the thermostat.

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The radiator core has become clogged. This is a problem for older and high mileage vehicles. Oxidation, scale, and sludge can conspire to clog the radiator core. It can even be the result of adding too much stop leak to the system. Using a good quality radiator flush in the cooling system may help, but probably you are headed for a radiator replacement.

Your radiator cap needs to be replaced. Without a radiator cap pressure tester, it can be quite difficult to diagnose. If your radiator is spilling fluid around the cap as soon as you stop the vehicle when it is overheating, you have found the problem. Unfortunately, this is not the usual symptom of a bad cap. If you have a shop or parts store in town with a cap tester, take it in and have them check it for you.

You have a blown head gasket. Usually large amounts of white smoke billowing from your exhaust pipe will tell you that coolant is pouring into your car's cylinders. If it leaks to the outside, you will see puddles of coolant under your car that are not located near anything that should leak. In extreme cases, the car simply will not start after you have turned it off when it is hot.

If you or a co-worker is in an accident and you need replacement parts for your medium or heavy duty commercial truck, call us at (803) 564-3228 or (877) 564-6307. If you have any difficulties getting through our phone system, please use our Contact Form or Parts Request Form, or email sales@busbeetruckparts.com.

We have hundreds of Salvaged Medium Duty Trucks and Commercial Box Trucks for Parts including: Isuzu, Mitsubishi Fuso, UD, and GMC. With thousands of parts, including our most popular Isuzu NPR Truck Parts, we should have any part that you need in stock. Our sales professionals will be glad to assist you.  We are located at 4107 Festival Trail Rd, Wagener, SC 29164.


Be sure to Subscribe to the Busbee Blog for more helpful tips and tricks for safe and easy driving. Follow us on Facebook and Twitter, and sign up for our Free Monthly Newsletters.

Medium Duty Truck Spring Maintenance Check List

Spring is here, and as the seasons change we recommend you keep in mind these 8 things we've placed at the top of our Spring Maintenance Check List for Isuzu, Hino, Mitsubishi Fuso or Nissan UD medium-duty box trucks.

Check your wheel alignment

For your vehicle to handle safely and properly you need to have your wheels in alignment. This also helps so your tires don't wear out prematurely.

Related:  Proper Tire Care for Isuzu, Mitsubishi, UD, GMC Medium Duty Trucks: How To Make Your Tires last Longer

Check the belts and hoses

A broken belt or hose can cause many problems, from the loss of power steering to an overheated engine. Look for cracks and peeling on the belts, softening on the hoses.

Check the battery

Winter can be tough on all the starting components like the starter and alternator. If the battery is older than three or four years, start expecting problems. To avoid a dead battery before it's too late, pay attention to the signs of a weak battery such as dimming headlights or interior lights. Take a look at your driving habits. Remember, short trips and long periods of inactivity will sap a battery's life. Take a look at the battery itself. Corrosion or stains mean you have a leak.

Check your spark plugs

Worn-out spark plugs can drastically reduce your fuel efficiency. Its always a good idea to check your spark plugs at least two times a year, before the winter and summer seasons. You should replace them if needed.

Check your coolant

When the temperatures rise it's important to make sure your car's engine is getting adequately cooled. If the coolant light on your dash is on or if you simply haven't checked the coolant level in a while, make sure the fluid is at the proper level. Most cars have a fluid level gauge, so consult your owner's manual to find out how to check the level on your particular model. Make sure you only open the coolant cap when your car is cool. Opening the cap when your car has been driven can be very dangerous.

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Check the brakes

Winter conditions and salt on the roads can lead to corrosion of brake parts. Nothing is more crucial to your safety than your brakes, so get them checked. Trouble signs: pulling to one side when you hit the brakes, squeaking or grinding noises and a brake pedal that feels too soft.

Check the tires

Checking the air in your tires should be done at least once a month. Checking your tire tread is something you should do several times a year. Try the coin test on your tires: Insert a quarter into several grooves across each tire. If part of Washington's head is always covered, you still have 4/32 inch of tread left and can probably drive safely. If you have less tread, it's time to think about replacements. (A definite danger signal comes when you slip a penny into a groove and the tread does not reach Lincoln's head.)
Even if your tire tread is OK, make sure you keep them inflated to the pressure listed on the placard visible when the driver's door is open. Properly inflated tires help you save money on gas. To get an accurate reading, check the pressure of tires when they are cold, not when you have been driving. Also, if there is excessive wear on the edge of any tires, it may be time for a new set and a four-wheel alignment.

Check your oxygen sensor

This one is obscure, but it is important to gas mileage. Because the sensor helps set the fuel mix going into your engine, a faulty one can cause too much gas to be used. Replacing the sensor needs to be done every 30,000 to 50,000 miles.

Getting a spring checkup for your car not only could avoid a summer breakdown, it could save you money on your monthly gas budget.

If you or a co-worker is in an accident and you need replacement parts for your medium or heavy duty commercial truck, call us at (803) 564-3228 or (877) 564-6307. If you have any difficulties getting through our phone system, please use our Contact Form or Parts Request Form, or email sales@busbeetruckparts.com.
We have hundreds of Salvaged Medium Duty Trucks and Commercial Box Trucks for Parts including: Isuzu, Mitsubishi Fuso, UD, and GMC. With thousands of parts, including our most popular Isuzu NPR Truck Parts, we should have any part that you need in stock. Our sales professionals will be glad to assist you.  We are located at 4107 Festival Trail Rd, Wagener, SC 29164.

Be sure to Subscribe to the Busbee Blog for more helpful tips and tricks for safe and easy driving. Follow us on Facebook and Twitter, and sign up for our Free Monthly Newsletters.