10 Ways You’re Killing Your Diesel

Easily Avoided Common Mistakes

Jason ThompsonMay 1, 2012
Since the cost of replacing the diesel engine in your pickup is about the same as buying a new car from the dealership—it’s important to keep it alive as long as possible. Although almost everyone thinks of themselves as diesel experts, bad maintenance and usage practices abound. We know this because these easy-to-fix mistakes are keeping diesel shops very busy across the country. We’ve made a list of the top 10 deadly sins, which are damning far too many diesels to an early demise.
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1. You’re Not Changing Your Fuel Filter
A clogged fuel filter can damage expensive injection pumps and injectors. Diesel fuel injection systems create a great deal of heat, and they rely on unobstructed fuel flow to keep the pump and injectors cool. As the fuel filter plugs up, the flow of fuel is restricted. In extreme cases, this extra pressure can cause a filter failure, which sends contamination directly into the injection system.
2. You’re Not Changing Your Air Filter
When the air filter gets clogged, fuel economy begins to suffer. A clogged air filter also causes the turbo to spin faster as it attempts to supply the engine with air. If dirt gets past the air filter because it was not installed properly or there is a leak in a boot—severe turbo, valve, and piston engine damage can occur in minutes. Driving down a gravel road may be all it takes to scour the cylinder walls.
Changing your in-cab air filter on a regular basis will make your fan motor live longer and keep your hard-to-clean air ducts less dusty. This will make you want to keep your truck alive longer.
3. You’re Not Changing Your Oil
Oil filters are important because they remove contaminants found in the oil. Oil analysis laboratories examine samples of oil from diesel engines and can determine a motor’s health without performing major surgery. The tests include a spectral exam that establishes the amount of wear metals in the oil, which indicates the level of bearing failure or other mechanical problems. Silica (dirt) is by far the biggest factor in engine wear and intrudes past seals and filters. As it combines with carbon, silica forms an abrasive called carborundum, which is similar in hardness to diamonds.
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Silicone is an oil additive and anti-foaming agent also measured by the labs. From this information, you’ll be able to see how far you can extend your oil change. Coolant in the oil can indicate a major engine problem—some say glycol is the number one engine killer. The flashpoint of the oil is also typically tested. This information will tell you if you have fuel in the oil, which also accelerates engine failure.
4. You’re Forgetting to Mind Your Fluids
It’s important to change your engine oil, coolant, transmission fluid, and power steering fluid. One look inside the valvebody of a modern automatic transmission reveals the precision internals that need clean fluid in order to operate properly. Not adding a bypass engine and transmission oil filter to your engine isn’t murder, but it could be considered neglect. These devices work by screening the fluid down to 3 microns or less—that fine filtering would clog a full-flow filter. They can do this by only taking a small amount of oil at a time—so as not to affect normal flow. Installing a coolant filter is like giving your truck a liver or a kidney. Although the initial expense hurts—your truck will pay you back. Bad coolant will clog passages, which will cause overheated parts.
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5. You’re not Letting Your Engine Warm Up
Don’t be that guy who starts his cold engine and immediately revs it up. The only thing you’re showing off is that you don’t know your turbo and engine bearings won’t get lubricated properly with cold, thick oil. Let your engine warm up like you warm up in the morning. Let the glow plugs and intake heater do their job. Fire the engine and give it some time for the combustion heat to warm the engine evenly.
This practice is very important on extremely cold mornings. Hot and cold engine parts expand at different rates, so gaps can form, which could cause leaks or gasket failures. Wait until your engine oil and coolant temperature gauges show you are in the right operating range. You do have these readings…don’t you? Also, if it’s really cold, don’t turn the steering wheel too much right away or you could risk blowing a hydraulic hose. The other thing that’ll keep your engine running longer is preheated coolant. The more cold-starts your diesel is subjected to, the shorter its lifespan will be. Inconsistent metal expansion and poor-flowing (thick) lubricants don’t provide protection from moving parts.
Another thing to worry about is fuel washing the cylinder walls before compression ignition can occur. Here is a message we got from a reader from the North Pole: “I have both batteries heated, the block heated, and two heating pads on the oil pan. The transmission is not heated, because it’s a stick. The intercooler is totally blocked as well. I might just put a pad on the transfer case and front differential, but it warms after about a mile of driving in four-wheel drive.” Diesel-fueled auxiliary heaters are also an option. It’s also just as important to let your diesel cool off before you shut it down. A turbo timer will do this automatically for you, because if it gets shut off too soon, oil will overheat, break down, and destroy turbo bearings.
6. You’re Not Reading the Smoke Signals
Don’t assume you can get by with worn-out injectors. If your truck is smoking black more than usual, that’s a possible sign your injectors need replacing. Another sign they are bad is if they start making noises. A diagnostic tool is able to individually shut down each injector to see which one is the culprit. White smoke often indicates coolant in the combustion chamber—either a sign of a head gasket failure or EGR cooler failure (if equipped). Blue smoke usually indicates engine oil in the combustion chamber—either from leaking piston rings or a bad valve seal. Insufficient compression can also cause a smoky engine.
7. You’re Not Keeping Your Truck Clean
Even if your truck is in perfect mechanical shape, it can still fall apart underneath you because rust never sleeps. Those who live in the Southwest don’t really have to worry about rust because it is too dry for the chemical reaction to take place. Everybody else should make it a point to keep paint chips filled with touchup paint and have a fresh coat of wax applied at least three times a year. During the winter months, when chemicals are applied to the roads to melt ice, you can’t wash your truck enough. During the rest of the year, avoid splashing through puddles, make sure your mudflaps are functioning, and try to avoid gravel roads if possible.
8. You’re Overheating Your Engine
We’ve watched the vicious cycle of modify, race, and then destroy one’s engine play out more times than we’d like to see, but some people still don’t believe certain truths until they learn them the hard way. When making any modification to your diesel, it’s absolutely necessary to keep track of all the engine temperatures. Even stock vehicles can use the extra insurance that comes with knowledge of the coolant, exhaust gas temperature (EGT), and engine oil temperature. You can also use this information to diagnose oil coolers or cooling system failures.
9. Centrifugal Force Is Wearing Your Truck Out
For those on a tight budget, the unforeseen cost of a new set of tires (because the old ones prematurely wore out) can be a truck’s death sentence. Poor alignment, along with under-inflated tires, can cause bad fuel mileage and tires with uneven wear patterns. A bent rim or severely unbalanced tire can cause axle-bearing failure. An out-of-balance driveshaft can cause axle pinion bearing wear and transmission or transfer case damage. It’s also important to keep the U-joints greased or replaced. Driveline maintenance also includes changing your differential fluid.
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10. You’re Poisoning Your Fuel Tank
According to the marine diesel industry, most engine problems begin in the fuel tank. This is because water intrusion is more present on the seas than it is on land. Still, according to BP, “Under normal storage conditions, diesel fuel can be expected to stay in a usable condition for 12 months or longer at an ambient of 68 degrees Fahrenheit.” Yet the lifespan of diesel drops to, “6 to 12 months at an ambient temperature higher than 86 degrees Fahrenheit.” As diesel fuel ages, BP points out that, “fine sediment and gum forms in the diesel brought about by the reaction of diesel components with oxygen from the air. The fine sediment and gum will block fuel filters, leading to fuel starvation and the engine stopping. Frequent filter changes are then required to keep the engine going. The gums and sediments do not burn in the engine very well and can lead to carbon and soot deposits on injectors and other combustion surfaces.”

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