Turbochargers rarely fail without warning. A loss of power, unusual noise, increased oil consumption, or excessive smoke can all be signs that something in the turbocharger system needs attention.
The good news is that you may be able to spot some of the most common turbocharger failure symptoms with a quick inspection before the problem turns into unexpected downtime or a more extensive repair.
But there’s an important distinction to make:
A symptom isn’t the same thing as a diagnosis.
Many symptoms associated with a failing turbocharger can also be caused by problems elsewhere in the engine, intake, exhaust, or lubrication system. Before replacing a turbo, take the time to inspect it and determine what is actually causing the problem.
Here’s what to look for—and what a five-minute turbocharger inspection can tell you.
What Are the Most Common Signs of a Failing Turbocharger?
A failing turbocharger can show up in several ways. While no single symptom proves the turbo itself is bad, these warning signs are good reasons to investigate further.
Loss of Power or Slower Acceleration
One of the most noticeable signs of a bad turbo is a change in engine performance.
The turbocharger helps provide the airflow the engine needs to produce power. If the engine isn’t receiving the boost pressure it needs, you may notice reduced power, slower acceleration, or a truck that doesn’t respond the way it normally does.
However, low boost doesn’t automatically mean the turbocharger has failed. Charge-air leaks, intake restrictions, exhaust problems, and other engine issues can produce similar symptoms.
Unusual Whining or Whistling
Turbochargers naturally produce some noise during operation. What matters is a change from what is normal for your engine.
A new or unusually loud whining or whistling sound may indicate an airflow problem or another condition that requires inspection. Depending on the cause, changes in turbo noise can be associated with leaks, wheel damage, bearing wear, or other problems within the system.
Grinding or Scraping Noises
Grinding, scraping, or other mechanical noises are more concerning.
These sounds may indicate internal component damage or that the compressor or turbine wheel is contacting its housing. If you hear an abnormal mechanical noise coming from the turbocharger area, further inspection should be performed before continuing to operate the engine.
Excessive Exhaust Smoke
A noticeable change in exhaust smoke can also indicate that something isn’t operating correctly.
Smoke can have many causes, so it shouldn’t be used by itself to condemn a turbocharger. When excessive smoke appears alongside other symptoms—such as increased oil consumption, loss of boost, or abnormal turbo noise—it provides another reason to investigate.
Increased Oil Consumption
If the engine begins using more oil than usual, the turbocharger and its lubrication system may be among the areas worth checking.
Increased oil consumption can be associated with lubrication, sealing, drain, or other engine-related problems. Before replacing the turbocharger, determine where the oil is coming from and why.
Excessive Oil in the Compressor Housing or Charge-Air Piping
Finding oil in the turbo can immediately raise concerns, but it doesn’t automatically mean the turbocharger is bad.
A light oil film may be present under some operating conditions. Significant oil accumulation, particularly when combined with increased oil consumption or other symptoms, warrants further diagnosis.
The 5-Minute Turbocharger Inspection: What to Check
If you’ve noticed potential failing turbocharger symptoms, a quick visual inspection can help reveal obvious problems and determine whether further diagnosis is needed.
Before beginning, make sure the engine is shut down and the turbocharger has cooled sufficiently. Always follow the appropriate service procedures for your specific engine and application.
Step 1: Inspect the Compressor Wheel
Remove the intake piping as appropriate for the application so you can visually inspect the compressor wheel.
Look closely for:
- Chipped fins
- Cracked or bent blades
- Signs of contact between the wheel and housing
- Foreign-object damage
- Other visible damage or abnormal wear
The compressor wheel should rotate freely without obvious contact with the housing.
Visible blade damage or evidence that the wheel has contacted the housing is a sign that additional inspection is needed before returning the engine to service.
Step 2: Check Turbo Shaft Play
With the compressor wheel accessible, check the turbocharger shaft for abnormal movement.
This is an area where it’s especially important not to jump to conclusions.
Some side-to-side, or radial, movement may be normal depending on the turbocharger design and whether the unit has oil pressure.
What should raise concern is excessive movement, evidence that the wheel is contacting its housing, or concerning in-and-out, or axial, movement.
There isn’t one universal measurement for acceptable turbo shaft play across every diesel turbocharger. Always refer to the specifications and service information for the specific turbocharger you’re inspecting when determining whether shaft movement is within limits.
Step 3: Look for Excessive Oil
While you’re inspecting the compressor side of the turbocharger, look for excessive oil accumulation.
A light oil film doesn’t automatically indicate a failed turbo. A significant amount of oil, particularly when accompanied by increased engine oil consumption, smoke, or other symptoms, deserves further investigation.
The important question isn’t simply:
“Is there oil in the turbo?”
It’s:
“Why is the oil here?”
Oil supply and drain issues, engine operating conditions, and other problems can contribute to oil appearing around the turbocharger or charge-air system.
Treat the oil as a symptom that needs to be investigated—not a diagnosis by itself.
Not sure what you’re seeing? Call HHP at 844-304-7688. Our parts specialists can help you identify the right next step for your application.
How Much Turbo Shaft Play Is Normal?
Because turbo shaft play is commonly used to judge turbocharger condition, it’s worth looking at more closely.
The turbocharger shaft connects components that operate at extremely high speeds. Depending on the bearing system and turbocharger design, some radial movement may be present when the engine isn’t running and oil pressure isn’t present.
That doesn’t automatically mean the turbo is failing.
Excessive movement becomes more concerning when the compressor or turbine wheel can contact its housing or when there is abnormal axial movement.
Rather than relying on a universal rule for how much movement is “too much,” compare the turbocharger against the manufacturer’s specifications for that particular unit.
Is Oil in the Turbocharger Normal?
Seeing oil around a turbocharger often leads to one immediate conclusion: the turbo is bad.
That’s not necessarily the case.
There is an important difference between a light oil film and excessive oil accumulation.
If you’re finding a significant amount of oil in the compressor housing or charge-air system, additional diagnosis is appropriate. However, oil around the turbocharger doesn’t prove that the turbo itself caused the problem.
The source of the oil and the operating conditions surrounding it matter.
That’s why oil in the turbo should be treated as another diagnostic clue rather than automatic proof that the turbocharger needs to be replaced.
Do These Symptoms Always Mean the Turbo Is Bad?
No.
This is one of the most important things to remember when diagnosing diesel turbo problems.
Loss of boost, smoke, increased oil consumption, and unusual noises can point you toward the turbocharger, but other problems can create similar symptoms.
Depending on the application and symptoms, diagnosis may also need to consider:
- Charge-air leaks
- Intake restrictions
- Exhaust leaks or restrictions
- Oil supply or drain problems
- Other engine-related issues
That’s why replacing a turbocharger based on one symptom alone can lead to an expensive misdiagnosis.
Don’t ask only, “Is my turbo bad?” Ask, “What is causing this symptom?”
Inspecting the complete system can help determine whether the turbocharger is actually the root cause or simply where another problem is showing up.
Need help identifying your turbo or finding replacement options for your application? Call HHP at 844-304-7688 or shop our selection of replacement turbochargers.
What Happens If You Ignore a Failing Turbocharger?
If a turbocharger is actually damaged, continuing to operate the engine can allow the problem to become more severe.
Depending on the type of failure, potential consequences can include:
- Additional compressor or turbine wheel damage
- Loss of boost and engine performance
- Increased oil consumption
- Component or metal debris entering other parts of the system
- Additional engine or aftertreatment concerns
- Unexpected downtime
Catching an issue early gives you an opportunity to diagnose the cause before the failure progresses.
A quick inspection in the shop is considerably easier than dealing with a major failure on the road.
When Should You Inspect Your Turbocharger?
You don’t need to wait until the engine has completely lost boost or the turbocharger has stopped working.
Consider inspecting the turbocharger and related systems when you notice a new or unexplained:
- Loss of power or slower acceleration
- Whining, whistling, grinding, or scraping noise
- Increase in exhaust smoke
- Increase in oil consumption
- Oil accumulation in the compressor housing or charge-air piping
- Change in overall engine performance
A five-minute turbocharger inspection won’t diagnose every possible problem, but checking the compressor wheel, shaft movement, and oil accumulation can reveal obvious warning signs and help determine what needs to happen next.
The goal isn’t to find a reason to replace the turbo.
The goal is to correctly identify the problem before it becomes a bigger one.
Need Help Finding the Right Replacement Turbocharger?
If your inspection and diagnosis point to turbocharger replacement, Highway & Heavy Parts can help you find the correct turbo for your diesel engine application.
HHP carries replacement turbochargers for popular diesel applications, including International/Navistar engines, along with turbocharger options for other major diesel engine makes.
Have your engine information and current turbocharger information available when you call so our parts specialists can help identify the correct replacement for your application.
Call HHP: 844-304-7688
