Tech Tips: Common Diesel Turbocharger Problems

Modern diesel engines all have turbochargers. Boosting your internal combustion engine’s potential both physically and figuratively is nothing new. Diesel engines have been taking advantage of wasted exhaust gas for decades. 

Diesel Red VGT TurbochargerIt is one of the best and most efficient ways of getting added power, torque, and throttle response to an otherwise lazy setup. Diesel engines are renowned for making incredible torque but have not been known for having much “pep in their step”. Luckily, engineers figured out very early on that adding a turbocharger will increase horsepower and torque. It is now looked at as a necessary requirement for any diesel engine.

Do you think that your turbocharger isn’t working at peak performance? Has smoke and soot increased? We’re here to help you understand how a modern turbocharger works and what can cause it to fail prematurely. For those who want a more in-depth look, Highway & Heavy Parts has already put together a handy failure diagnostic checklist guide. It is intended to help you determine if your turbo is at the core of your engine problems.

However, a checklist only serves as a guide, and understanding why turbochargers fail in the first place is just as important. Have a look at some of the most common issues that cause them to fail.

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Turbo Problems on The Compressor Side

Plugged Air FilteR

It shouldn't come as a surprise, but preventative maintenance is extremely important. To get as much power as possible, an unrestricted airway is imperative. But we can't have intake air mixed with dust, dirt, and debris going into a turbocharger that spins upwards of 60,000 RPM. 

A plugged air filter can cause a vacuum on the compressor side, which can result in it drawing oil and cause a “runaway”. There are several videos online but the gist of it is that your diesel engine can no longer be stopped by simply cutting the ignition. Little details such as keeping your air filter clean can help keep the oil seals from unnecessary wear and potentially help prevent serious issues.

Crankcase Pressure

Too much air pressure in the crankcase can have devastating results. It is another common problem that can bring turbo seals to the brink of destruction. This issue can be easily noticed thanks to engine oil making its way on both the compressor and turbine side. Oil is meant to cool down a turbocharger and should at no point be present in the intake or exhaust housings.

The most common cause of increased crankcase pressure is a blocked crankcase breather. Every part of your diesel engine, no matter if you got a CAT 3406E or just a six-cylinder Cummins, is made to run within very specific tolerances. Take the oil cap off and feel for any excessive air. If the breather seems fine, it may be a sign that your piston rings are beginning to fail and will need a full rebuild.


Turbo Problems On The Turbine Side 

Restricted Drain Line

The drain line on a turbocharger system is meant to return the oil used to cool the system back to the engine. Sometimes, especially with old high-mileage engines, the oil return lines can become blocked off. 

If the oil has no way to get back into the crankcase, it will push its way past the seals and end up on the turbine side. In certain cases, the drain line used can end up swelling and cracking due to the extreme temperatures that a turbocharger produces. A small silicone heat-proof hose can be all that’s needed to stop any further problems. When in doubt, swap it out. 

Defective Valve or Piston Rings

The valve seals and piston rings in a diesel engine have several jobs to do, but none of them include allowing oil to thorough. Over time, both the valve and piston rings become worn to the point that oil can travel past. 

Oil can then make its way to the exhaust and in the turbine side of the turbocharger. A little oil is good for it, right? Wrong! A turbocharger should be lubricated, but not via leaking piston and valve rings. The most common sign of worn or defective piston rings is blue smoke coming from the exhaust. Most times, removing the intercooler hoses will confirm your thoughts by having leftover oil inside.

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Common Turbo Problems 

Damaged Compressor Wheel 

As previously mentioned, the turbochargers on a diesel engine can spin upwards of 60,000 times per minute. At that rate, even the smallest imperfection or foreign debris can cause havoc on the compressor wheel and housing. 

If the fins are bent, damaged, or even missing, the housing will effectively destroy itself from the inside out. The bearings on your turbocharger are also a key component. They should be inspected periodically for play or excessive wear by a qualified technician. It is one of the many services we offer here at Highway & Heavy Parts.

Damaged Turbine Wheel 

Much like the compressor, the turbine side works within extremely tight tolerances. Any damage or deformation in the fins or housing can spell disaster for a turbocharger. Why does this happen? It could be several things, but most times turbine wheel damaged is caused by foreign objects entering the exhaust manifold. 

Of course, bearings could be to blame for problems associated with damaged turbine wheels, and in severe cases, it’s the engine spitting out bits of material. Once they enter the turbo, it's just a matter of time before total destruction takes place.

Turbo Bearing Failure Common Causes

To sum it all up, turbochargers can fail one of several ways on both the compressor and the turbine wheel. Here are some of the most common causes of diesel engine turbocharger malfunction.

  • Poorly maintained system. Something as simple as not changing your air filter on time can have severe consequences later down the road. Most importantly, changing your oil regularly can help keep both your engine and turbocharger in top running condition.

  • Loose clamps. The bearings on your turbocharger are made to take a beating, but the system can't last forever. No matter if you are an owner, driver, or mechanic, periodically checking that all clamps and hoses are intact is one of the best safety precautions one can take.

  • Oil Starvation. Cooling isn’t the only thing that engine oil is used for on a turbocharger. The “black gold” as some refer it to, has another important role. This is known as lubrication. If there is a lack of oil going to the turbo bearings, the friction and heat created by metal-on-metal contact will quickly devour them. 

  • Wastegate malfunction. For a better understanding of how a wastegate operates, read our “How Does a Wastegate Work On A Diesel Engine” article. It’s important to know that a wastegate operates within set parameters and should not be removed or have any hoses “pinched off”.


Final Words

Turbochargers are ingenious and revolutionary pieces of modern engineering. Without a functional turbocharger, diesel engines would be extremely slow. As a result, your truck or heavy-duty equipment would take a long time to get up to speed. 

Highway & Heavy Part’s ASE-certified techs are standing by and ready to answer any potential questions you might have about turbochargers or diesel engines in general. Give us a call at 844-215-3406 or request a quote online today!

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