Our survey customers often ask us about how they should
perform diesel maintenance. This is a very easy question to
answer.
We've yet to see a diesel manufacturer that did not produce an excellent manual. They also provide a book-size parts manual. If you read and follow the one, you should have little use for the other. Diesel manuals contain every bit of information you need to know about how to maintain your engines, and more. What follows is a general discussion of what you should do and why you should do it.
One of the reasons why people often do not follow these instructions is because the frequency of recommended maintenance is a little bit more than the boat owner bargained for in terms of time and cost. In fact, our experience is that 80% of all the engines we see, in terms of the maintenance condition, come nowhere close to what the manuals recommend.
There are two fundamental points to diesel maintenance: Lubrication system Cooling System
This is what happens to pistons after an overheat. The piston is distorted and the rings are stuck, frozen into the ring grooves. This then caused blow-by into the crankcase.
High exhaust emissions into the crankcase then caused an acid build up in the lube oil that resulted in this bearing erosion. Eventually this will result in bearing failure. The root cause, however, was lack of cooling system maintenance.
Few people are unaware that diesel lube oil must be changed frequently, 100 hours is the usual interval. Why so often? It's because large amounts of carbon is a by-product that ends up in the oil. If allowed to build up and remain in the oil, the lubricating ability of the oil is severely retarded. Moreover, carbon blocks heat transfer and retards the cooling function of the oil as well. Engine oil will also suffer a build up of sulfuric acid, which can damage bearings as shown above.
Equally important is good filters. Believe me, only the very best and most expensive oil filters are good enough to be significantly effective. I recommend that you buy either OEM or top name brand filters regardless of cost.
Don't cheat on your lube oils, either. The manufacturers are not blowing smoke, so just follow the recommendation for oil grades. They know better than your buddy down the dock who may have other ideas that he heard from yet someone else.
We don't know the exact percentage of engine failures that result from lack of cooling system maintenance, but it is surely at least 50%. You need to understand this: Diesel engines operate under a piston compression of around 350 to 550 psi. That is three to four times the amount of a gas engine. This high compression puts great strain on the engine and can build up heat very rapidly (like within 60 seconds) if there is a failure in the cooling system. Diesel cooling systems are vastly more critical than gas engine cooling systems. Gas engines can suffer from numerous moderate overheats without causing catastrophic damage. THIS IS NOT TRUE OF DIESELS. Diesel engines can and will suffer serious damage even as the result of relatively minor overheat conditions. This is because the overheating occurs so rapidly, and because the internal parts are less tolerant of damage than a gas engine.
Most overheats occur because the engines are never inspected and leaks are never found and repaired. Cooling system hoses are allowed to age, and they eventually burst, leak or blow off.
Another common cause is failure to keep the cooling system clean. Instead of adding a properly mixed solution of recommended coolant, owners just pour water in, or add straight coolant. Proper ratios of engine coolant are critical to proper cooling and the prevention of corrosion.
Due to vibration and age, system gaskets do not last forever and will inevitably start to leak. The leaks usually occur in a location that is not easily seen. Thus coolant is lost and the engine overheats. Consider this: Can you take a guess at how often anyone ever checks the engine coolant before starting the engines when we do a sea trial? The incredible answer is that not only do boat owners not check the coolant, they don't check the oil either. These very confidant souls who are going to eventually pay the price for their carelessness.
If your engines or any part thereof vibrate to the point where it looks blurry, or you can see it shaking, rest absolutely assured that that vibration is capable of destroying your engine. First of all, it's going to break all of the gasket surfaces loose. Or hoses will go loose. And then the engine is going to start leaking fluids. If the engines are vibrating excessively, you need to have the problem diagnosed and get the vibration stopped.
You should regard your alarm systems like light bulbs in your house. They will operate for a short period of time and then crap out. They are a constant maintenance thing, and the failure to maintain them could be one of the costliest mistakes you'll ever make.
One of the weaknesses of water temperature alarms is that they will not function when there is a complete loss of cooling water around the sensor. The sensor only works when it is immersed in water. For this reason, I strongly recommend that you have exhaust temperature alarms installed. These will function when the others won't. The cost of having them installed is minimal, and a drop in the bucket compared to the cost of an overheat.
Engine coolant should be checked every time before starting the engine. That does not mean looking at the coolant recovery tank. You should NEVER use the recovery tank as an indication of coolant level in the engine. Half the time these things do not work properly.
The first sign of leaking gaskets does not mean that you should replace THAT gasket. it means you should replace all such gaskets. If one is starting to leak, soon they all will.
All diesel will have at least three coolers: the heat exchanger, oil and fuel cooler -- and most likely a transmission cooler. That makes four for a single engine boat, eight for twin. The problem here is that they all need to be inspected and serviced at least annually. Yes, you are correct. Servicing eight coolers is expensive. But, then, so is overhauling or replacing an engine or two. This is one reason we posit the question of whether you can really afford diesels or not. Many boat owners simply cannot afford this, and so run their engines till they quit. Or put up the for sale sign when it starts blowing smoke.
Why is this necessary? Several reasons. You replace the zincs on your boat at least once a year, but perhaps you weren't aware that your engine is full of the same saltwater that your boat is floating in. If you have corrosion problems on the hull of your boat, then you have corrosion problems inside your engine. Not inspecting the cooling system annually (by means of dismantling it) is like trusting the weather forecast. Another reason is that sea strainer do not take out all foreign material, and deposits of debris can build up inside. Or, if you are operating in very sandy, silty water, abrasion and erosion of the core and other components may be taking place.
Faults within the fuel system generally do not cause engine damage, but it does cause damage to itself, as well as serious performance problems. Nowadays it is rare that diesel boats don't have good Racor or Dahl filters. But it is not rare that many boats have dirty fuel system problems, whether the contaminated fuel results from internal conditions, or taking contaminated fuel on board. Some of the better fuel docks today have open filters where you can actually see whether any contamination is being removed from the fuel. To say the least, this is comforting.
Unfortunately, water can accumulate in your tank. The most common way this happens -- and it's remarkable that most people never think of it -- is that the fuel filler cap is leaking. The second most common source is through an improperly installed vent line. The third is condensation in the tank. In southeast Florida tank condensation is fairly rare because temperature changes are not conducive. From the central west coast on north it is.
People often ask us whether they should maintain their tanks full at all times. The answer to this is not that straightforward. It depends on how much fuel you use. It is not wise to allow old and aging fuel to accumulate in your tank. If you top off after short, infrequent operation every time, the fuel in your tank is going to get old. This can foul up your injectors. But so will water. Water causes bacterial blooms in the fuel, and it only takes a very small amount of water to do this. To my way of thinking, you'd be better off with this happening to a nearly empty tank than a nearly full one. For the most part, it's going to depend on how much of a bacteria problem you have, and whether frequent changing of your filters can handle it.
Long winter layups present an obvious problem. If you have one of those fuel filtering services in your area, that is the way to go since the cost of filters and aggravation can more than make the cost of this service worthwhile. Plus it absolutely does the job.
Many boat builders are installing vent filters on tank vent lines. These need to be serviced, so don't forget about them or one day an engine may magically crap out for no apparent reason.
The temperature and cleanliness of the air your engine breathes is very important. That's why most engine manufacturers are now supplying some kind of air filtration system with their engines, after we've complained about engines breathing salty air for years. There's no end to the ways engines can end up breathing not only dirty air, but air that is full of all sorts of crap like sand. And yes, inside your boat. A typical example is on a trawler type boat with wooden soles. The gap in the hatches is directly over the air intake, and dirt from the sole falls right down the gaps and into the engine. One of the most common problems is engines sucking in crap from deteriorating carpeting backings. Yep, engines eating carpeting, fibers and all.
If you don't have air filters on your engines, get them installed NOW!
Turbo charged engines usually require that the air from the hot turbo be cooled. This is done with an inter or after cooler, take your choice of names. Not only do these gizmos cool intake air, but they filter it too. Not by design, but by the same means your air conditioner inadvertently filters air. This clogs the cooler up with a corresponding rise in engine temperature. If your cooling system is already weak, this can be fatal. Yep, you guessed it. Here's yet another cooler to add to the cost of the maintenance bill. You small boaters, are you really sure you want diesel? Get out the checkbook.
Yet another problem is air starvation. Fairly common, this is the result of improper boat design from inadequate ventilation. It, too, causes engine overheating. You can tell when this condition is present when, under way, you go to lift an engine hatch or door and there is a vacuum fighting against it. Another telltale is when you get a dark halo around the perimeter of carpeting and carpeted hatches. This is an absolutely sure sign that the engine room vents are not adequate.
The demise of most diesel engines is caused by the cumulative effects of improper maintenance and resulting overheats. Then, suddenly one day the engine goes bang for no apparent reason. There's a reason all right, but it's the cumulative effect of poor maintenance. For the most part, diesels are very unforgiving of neglect. Oh, I know you're probably thinking about those boating books you've read that talk about how rugged and dependable diesels are. I've seen them too. But if you look closely, you'll see that they are not talking about HI PERFORMANCE DIESELS.
They're talking about those old 4 and 6 banger naturally aspirated engines that develop 110 hp. Ninety-nine percent of diesel engines in power boats today can be classified as high performance. Meaning that they are not slow, rugged and dependable -- rather they are fragile engines that require a great deal of care. It doesn't take much to push them over the edge.
My first recommendation, if you are not doing most maintenance yourself, is that you establish a relationship with a good diesel man, if that is possible. Engage him to perform the following:
Maintain the engine alarm system. If the alarm system or gauges do not function, this could be one of the costliest mistakes you'll ever make.
Conduct a basic engine survey annually. This is essentially an inspection to search for small problems before they become big ones. The cost to do this is not high, and is likely to save you big bucks in the long run.
Inspect sea water pump impellers biannually.
Take engine temperatures with infrared gun annually.
Clean intercooler annually
Open up and inspect the sea water pump and check condition annually
Conduct cooling system inspection and cleaning every two years.
Change engine coolant annually.
Conduct a basic engine survey at beginning of season. This includes all gaskets, hoses, belts and wiring.
Inspect sea water pump impellers annually.
Conduct cooling system inspection and cleaning every two years.
Take engine temperatures with infrared gun annually.
Clean intercooler annually.
Change engine oil prior to lay up.
Change engine coolant every two years.
*These recommendations are not intended to supercede engine manufacturer recommendations.
Don't start engines without checking fluid levels.
Do not permit engines to sit without running them for more than 7 days. Try to operate engines at least every 5 days. Allow engines to warm up, then run at about 1500 RPM for about 5 minutes, then shut down.
Properly lay up engines that aren't going to be used for periods of greater than 30 days. Long periods of disuse results in serious internal engine rusting of cylinder walls and valves.
Do not start engines with throttles advanced. Do not race engines until they are up to normal operating temperature. This is very damaging.
Avoid prolonged idling if possible. When trolling or idling for long periods, always run the engine at cruise speed or higher on the way home for at least 30 minutes to dislodge carbon deposits.
Service fuel system immediately if excessive exhaust emissions occur. Do not operate boat at high speed with badly fouled bottom or when vibration occurs.
First posted June 30, 1999 at www.yachtsurvey.com.
Page design changed for this site.
Posted December 28, 1999
By Featured Writer Mike McGlothlin
For the most part, diesel long-blocks are pretty solid, with rigid components like forged-steel crankshafts and connecting rods, mammoth-sized wrist pins, rod bearings, and main bearings, gear-driven accessories, and densely-cast gray-iron blocks proving nearly unbreakable. Sure there are freak instances of dropped valves, bent rods, and cracked blocks, but by-and-large most light-duty, medium-duty, and heavy-duty diesel engines are hard to kill. However, outside of structural integrity, there are a host of issues—both mechanically and electronically as well as operator-induced and factory engineered—that can shut any diesel engine down. Cummins, CAT, International, Detroit, John Deere, or Mack, none of the big name manufacturers are immune to a bit of inevitable downtime.
For that reason, we’ve compiled a list of the 10 most common problems a diesel engine will face in its lifetime. From common-knowledge, hard-starting issues to the inherent vibration problems we’ve all heard about, to the modern-day diesel’s emissions-related headaches, our list runs the gamut. Of course, contaminated fuel, injection system failures, and cooling system troubles made the cut, too, with electrical gremlins, sensor failure, and oil dilution not far behind. Whether it be due to old age, system complexity, or lack of maintenance, the following problems represent the everyday ailments diesel owners are forced to contend with. It may be one of the uglier Top 10 lists you’ll find, but someone had to do it…
Vibration is inherent to all diesel engines and is primarily due to the violent, uni-directional combustion forces acting within the cylinders. This is true even in inline-six configurations, engines that are naturally balanced. But while slight vibration alone isn’t a major worry, it’s what happens over time that can be a problem. Or, worse yet, an increase in engine vibration, which is often a sign of a larger problem.
Unfortunately, as far as aged diesel engines are concerned, the answer to this question is unequivocally “no.” As service hours on an engine mount, the chances of vibration causing a problem to surface go up also. Many times, years of vibrant engine operation culminate in a fuel or oil leak. Without proper maintenance, different models of engines can be prone to certain failure points; for example, the DD15 can produce oil leaks when loose gasket seals appear around the fuel pump, oil coolant system, or air compressor. For fuel, the leak predominantly starts where a hard line and a fitting meet, but the occasional hairline crack in a steel fuel line is always possible. For oil, rear main seals, oil cooler O-rings, and even rusted out or damaged oil pans are behind most leaks.
While a fuel or oil leak can be traced back to the source and addressed quickly in most cases, an increase in engine vibration could be the sign of a much larger issue. Improper valve clearance, piston slap, injector misfire, and lack of compression can all contribute to inordinate amounts of engine vibration, and a process of elimination—whereby the easiest tests are run first—needs to take place for proper diagnosis.
Hard-start issues can usually be traced back to two primary points of causation with diesels: 1) batteries and starting aids, and 2) a lack of fuel. Diesel engines’ high compression ratios often require multiple batteries to be employed in order to provide enough cranking power to fire them up. However, failed or ailing glow plugs (if applicable) and glow plug relays or controllers (again, if applicable) can generate plenty of starting issues, especially in colder climates. To a lesser degree, non-functioning intake heater grids can cause longer crank times as well.
Outside of battery, glow plug, and grid heater issues, most hard-starting problems for diesels are fuel-related. A lack of low-pressure fuel supply and an inability to build adequate injection pressure will make a diesel a bear to turn over, and each of those respective issues can typically be followed back to a lift pump issue or a dead or dying injection pump. Because fuel injectors don’t normally all fail at once, the engine will start with an ill injector or two—though a problem will likely be noticeable, especially at idle.
No diesel engine enjoys firing up in the cold, but you can keep yours happy by ensuring a set of fresh or well-tendered batteries are always on board. Taking things a step further, it pays big dividends to have your existing batteries load-tested before cold weather arrives (i.e. fall). And finally, use your engine’s block heater (if applicable). After all, it’s there for a reason…and a diesel engine with ECT and EOT sitting at 50 to 80 degrees F over ambient temperature will always start easier than one sitting below zero.
This problem area doesn’t really apply to diesels produced prior to 2003-2004, but since these issues have been a part of life for on-highway engines for nearly two decades now, it would be negligent not to include it on our list. Exhaust gas recirculation and the elaborate exhaust after-treatment technologies that include diesel oxidation catalysts, diesel particulate filters, and selective catalytic reduction have become major weak links for the modern diesel engine. Even as manufacturers continue to refine and improve their emissions-fighting technology, most of the systems’ components remain prone to premature failure.
To meet tougher federal NOx emission standards that went into effect in 2004, on-highway diesel engine manufacturers turned to exhaust gas recirculation (EGR) to get the job done. By rerouting a portion of exhaust flow back into the engine’s intake tract (exhaust being almost completely void of oxygen), combustion temperature within the cylinders is reduced, which lowers NOx. The problem is that diesel exhaust is laced with soot, carbon, and vapor from blow-by, which clings to the walls of EGR coolers and especially EGR valves, eventually rendering them inoperable. We’ll also note that EGR is cooled off using engine coolant, which taxes the antifreeze considerably.
The OEM solution to more stringent federal particulate matter emission standards was the diesel particulate filter (DPF), a downstream exhaust device used to capture and store soot produced during combustion. Over time, the soot accumulation has to be burned off, and it’s transformed into fine ash through a process called regeneration. Regeneration can be either active or passive, but the former type requires that excess fuel be consumed, not to mention that the excess fuel is either injected on a cylinder’s exhaust stroke or through an additional fuel injector mounted downstream in the exhaust system. We’ll deal with the sensor side of DPF systems later on in our list.
Any form of debris infiltrating a fuel system is bad news, but the worst contaminant for a diesel to contend with is water—and this is precisely why water separators come equipped on virtually every diesel engine. But why is water so problematic? Because when it comes into contact with metal it leads to rust. Internal corrosion of fuel lines, pickup tubes, injection pumps, lift pumps, and injectors can precipitate their failure, cost you thousands in repairs, and, in a worst-case scenario, even destroy the engine.
Luckily for us, extensive studies have been conducted concerning water-in-fuel issues and we know that 99 percent of all fuel contamination issues begin in the fuel tank. Dirt, sand, grime, and other debris added via the filler neck is almost always captured by the engine’s fuel filter. However, water presents a unique challenge because, at the molecular level, diesel fuel is attracted to H2O. But on top of being attracted to water, diesel fuel will even absorb it. Biodiesel, which possesses an even higher affinity for water than regular number 2 diesel, compounds the problem further—as most fuel stations carry a biodiesel mix at the pump. Needless to say, water has always been and will always be an issue for diesel engines.
Like many issues on our list, proper maintenance goes a long way in preventing them. Because an unchanged fuel filter can only absorb so much water before it’s no longer effective, observing regularly scheduled fuel filter and water separator changes is of utmost importance. In addition, routine water separator drain intervals (if applicable) should be adhered to. It also pays to get your fuel from a trusted source, such as a high-volume filling station. High-traffic stations go through more fuel, which means the fuel they receive is always fresh. In closing, make sure to keep the fuel tank full whenever possible, as water vapor forms quickly in an empty or even a tank that’s half full.
To keep modern electronically controlled diesel engines equipped with exhaust after-treatment systems working flawlessly, a myriad of sensors have to be in good working order. But as many late-model diesel owners have found out the hard way, one failed sensor can lead to considerable headaches and lots of downtimes. Poor performance, limp mode, or complete inoperability, and check engine lights (CEL’s), and stored diagnostic trouble codes (DTC’s) are highly common when an emissions-related sensor stops working. For on-highway applications produced after 2007, the sensor failure problem is rampant.
Temperature, NOx, pressure differential, and even oxygen sensors are all required for proper diesel exhaust after-treatment system functionality. Failure of any one of these sensors can cripple engine performance. Temperature sensors are positioned before and after the diesel particulate filter to measure exhaust gas temperature (EGT). NOx sensors are used to determine the proper dosing of diesel exhaust fluid injected in applications that use selective catalytic reduction (SCR). Pressure differential sensors are also positioned upstream and downstream of the DPF, and they measure exhaust backpressure, with the pre-DPF sensor being the point of data collection for initiating the DPF regeneration process we mentioned earlier.
So which sensors fail most frequently? EGT sensors. Although they’re designed to work in extreme heat, their intense work environment often takes its toll on the thermocouple side of the piece, forcing them into early retirement. In some cases, EGT sensors are exposed to more than 1,600 degrees F—and very few components can withstand that kind of heat long-term. Other points of failure with EGT sensors (and indeed many other automotive sensors) stem from vibration or being disturbed when other areas of the exhaust system are being addressed or repaired.
Everyone knows that diesel engines are intended for hard work, but tackling the toughest of tasks on a consistent basis without proper cooling system maintenance or inspection can lead to overheating. Ignoring or allowing coolant leaks to go unaddressed, a failing engine fan, a stuck thermostat(s), or a bad water pump can all contribute to overheating. To a lesser degree, the incorrect type of coolant can also be a contributing factor. If improperly diagnosed or left unsolved, an overheating scenario could potentially lead to hard-part failure such as a warped cylinder head.
Older engines, especially those with hundreds of thousands of miles on the clock, are often still making use of the factory radiator hoses. For external inspections of leaks, this is the best place to start, followed by analyzing the condition of the hose clamps and then the radiator itself. If the source of a coolant leak brings you to the engine’s water pump, examine the weep hole (if applicable, or possible). If your search lands you at the thermostat housing, check it over for cracks. Of course, internal coolant loss could mean you’re looking at a blown head gasket or a cracked EGR cooler. More on the former issue in a bit.
In the midst of a busy work schedule, many diesel engines don’t receive the attention they truly deserve, and a plugged cooling stack due to neglect or a dirty work environment is a great example of that fact. Positioned out in front of the engine you’ll find the charge air cooler (i.e. intercooler), a large radiator, an A/C condenser, and in some applications a transmission cooler or even an oil cooler. These air-cooled heat exchangers are all fighting for adequate airflow to begin with, but when you restrict them further it’s a recipe for overheating. For the right candidate, thorough cleaning of the engine’s cooling stack—which entails disassembly, compressed air and low-pressure water with the use of a mild detergent—can bring operating temps at full load back down to where they need to be.
Now that we’re decades into full-on electronic control of diesel engines, wiring issues are surfacing throughout the repair industry. Bad connections, wire chafing, short-to-ground issues, and hard-to-identify intermittent electrical flare-ups are all in a day’s work for many of today’s diesel technicians. Tracking down electrical gremlins can be highly time-consuming with so many onboard systems present in late-model diesel vehicles. What’s worse is that what ends up being a simple wiring fix can initially lead you to believe a major engine component is bad, such as an injector. Proper diagnosis is paramount here.
Many times, a DTC or a blown fuse will guide you to the troubled area. In other instances, it might be obvious where you need to start. Regardless, before tearing into anything first look at your electrical connection points. Finding a loose connection or a corroded connector is more common than you think, and is always a welcomed “easy” fix. Damaged pins or wires at or near the electrical connection points can also quickly be discovered. In these cases you don’t even necessarily have to know what the wiring is for, you just have to address the obvious.
This problem often stems from number 1 on our list: vibration. Years and years of pulsation combined with the friction of a wire rubbing against a valve cover or anchor point can eventually wear a hole through the tape, wire loom, and/or a wire’s outer coating. At that point, the exposed wire’s contact with its surroundings can cause a textbook example of a short-to-ground. This is extremely common with engine harnesses. And while the issue is sometimes time-consuming to track down, the fix is cheap, often calling for electrical tape or an additional wire loom (or both).
This problem ties in with our “Emissions Equipment” entry due to many modern-era diesel engines making oil (as in, the level on the dipstick keeps rising) thanks to their regeneration events. If you recall, regeneration is the process that turns soot collected in the diesel particulate filter into a fine ash. To pull off this process, some engine manufacturers chose to inject excess fuel into the exhaust stroke of a given cylinder, which lights off the diesel oxidation catalyst downstream of the engine. The problem with this is that it washes out the cylinder wall, and some of the fuel inevitably squeezes past the piston rings and dilutes the engine oil.
The fallout from diluting the engine oil may not be immediate, but once the problems caused by it are noticed it’s likely way too late. First, engine oil that’s been contaminated with diesel fuel loses some of its viscosity, which obviously isn’t good for bearing life (mains, rods, cam, or even turbo bearings). But it isn’t just diesel that contaminates engine oil. In modern diesel engines, EGR introduces a considerable amount of soot particles into the oil. Increased oxidation is also common in diluted engine oil, which by breaking down the base molecules within the oil effectively reduces its service life.
Old engines or new, discovering fuel in the oil is commonplace and can happen for a lot of reasons. For one, a damaged cylinder, piston ring, or both is going to allow fuel left over from the combustion process to sneak into the crankcase. Short-trip operation, where the engine never reaches optimal operating temp is another common cause of fuel dilution. Additional reasons one might detect a higher percent fuel content (PFC), usually from the information provided on an oil analysis, can be linked back to excessive idle time, incomplete combustion, and improperly balanced or leaky fuel injectors. Interestingly, according to Amsoil, just 3.4 percent is the acceptable percent fuel content limit.
You might’ve noticed that we’ve referenced the difference between old and new diesel engines multiple times on this list…and now we’re doing it again. Pound-for-pound, modern-era injection systems simply do not last as long as their predecessors. However, in their defense, the injectors and injection pumps of today have more jobs to perform—and they also have to do it under higher pressure (hence the terms high-pressure common-rail injection and high-pressure fuel pump). To be sure, the mechanical fuel injection components of yesteryear have their wear points, too, but the service life of most of those systems was noticeably longer.
Whether they’re new-age common-rail or old-school pop-off style, poor maintenance can facilitate the early demise of any injector. Neglected fuel filter change intervals and low-quality diesel (including water contamination) are two leading causes behind injector failure, with deposit buildup and particle contamination not far behind (especially on common-rail injectors). Other than those contributors, the biggest killer of injectors is age and wear. Over time, internal wear items such as the ball seat, nozzle needle seat, and injector spring (to name a few) simply become worn out. Hard starting, rough idle, increased smoke, and added fuel consumption are all indicators of a bad injector.
A host of factors can contribute to the death of an injection pump. For starters, any lack of low-pressure fuel supply being sent to the pump can cause damage, as the injection pump relies on that 10-to-65 psi worth of supply pressure to not only lubricate the injection pump but to keep it cool as well. Then comes the poor quality fuel causality, with rust being a very common culprit in killing an injection pump (again, thanks to water). Then, just as with injectors, there are internal parts that simply wear out in time. But luckily, just as with fuel injectors, injection pumps can be rebuilt, bench-tested, and made like new again.
Thanks to the employment of multi-layer gaskets, large diameter bolts, and many times six fasteners per cylinder, most on-highway diesel engines aren’t notorious for blowing head gaskets. Still, others are infamous for lifting the cylinder head(s), pressurizing the cooling system, and costing the owner thousands in repairs (the Navistar-built 6.0L Power Stroke and CAT’s 3126 come to mind). However, even the seemingly “bulletproof” power plants of the light-duty, medium-duty, and heavy-duty segments can all succumb to this type of failure with age.
It can take hundreds of thousands of miles, but over the course of decades’ worth of heat cycles, the integrity of a diesel engine’s head gasket is perpetually being challenged. Eventually, be it due to the cylinder head flexing, shifting, or expanding one last time, the gasket’s ability to keep combustion in and coolant and oil out can fail to do its job. In other scenarios, where the engine has been reflashed (or mechanically turned up, depending on the engine) to produce more power, the limits of what the head bolts can handle are exceeded and they can stretch.
Like the upper sections of each cylinder bore, the cylinder head is exposed to both extreme heat and immense cylinder pressure. But it’s even deeper than that. The head gasket also has to resist the forces from the head flexing, vibration, and violent combustion that can scuff the block’s deck and the cylinder head’s surface. On top of that, the head gasket has to withstand the squish from the 200,000-psi worth of clamping force imposed across the length of its surface courtesy of the head bolts. Finally, the head gasket additionally serves to seal the pressurized antifreeze and engine oil running through it. Without a doubt, the head gasket is one of the hardest working gaskets in a diesel engine.