Turbocharger Diagnosis Tips

In today's post, we highlight some key tech tips for diagnosing turbochargers.

Vehicle manufacturers are adding turbos at a double-digit rate. Over the next five years, the turbo market is expected to grow to more than eight million turbocharged vehicles. As the number of turbocharged vehicles increases, more import technicians will see vehicles with turbocharger issues in their shops. But there's already confusion in the field. Here's a comment we recently received from the field regarding turbocharger repairs:

"It would be nice to have some diagnostic and visual checks to help know when a new turbo is needed."

To help technicians diagnose turbocharger repairs, here are a few important diagnostic and repair tips to keep in mind. As a note upfront, most turbocharger diagnoses (aside from noise and low power issues) require scan data and an understanding of operation at the technician-level.

What Causes a Turbocharger to Malfunction

Before we start, let’s highlight what causes a turbo to malfunction in the first place. Symptoms of a malfunctioning turbocharger include loss of power, excess smoke, high fuel consumption, overheating, high exhaust temperature, and oil leaks from the turbo. But it’s important to note that defects in other components can produce the same symptoms. Before wrongly attributing the issues to the turbo, remember that turbo performance can only be impaired by mechanical damage or blockage caused by debris.

Signs of a Damaged Turbocharger

Signs of a Damaged Turbocharger

If you hear whistling noises coming from the turbo, it’s likely due to an air/gas leakage caused by pre-turbine exhaust gas or air/boost leaks. Your first course of action should be checking all of the joints. If the noise continues, check the turbocharger clearances and wheels for housing contact.

If the turbocharger rotor assembly has seized up or is difficult to rotate, the problem is likely tied to the degradation of the lubricating oil. When the oil degrades, it can lead to carbon buildup in the bearing housing interior. The carbon buildup will ultimately restrict rotation. Two other issues that can cause the rotor to seize up include insufficient or intermittent drop-in oil pressure and dirt in the lubricating oil. Another important detail to keep in mind is that a turbocharger has specific axial and radial rotor clearances. Sometimes, the clearances can be misdiagnosed as worn bearings. In reality, clearances that are out of specification may be associated with a lubricating oil issue. Check for insufficient oil, dirt ingress, and oil contamination with coolant.

To determine if the turbo has been damaged by foreign material, inspect the turbine wheel or impeller. You will clearly see any foreign material that has entered through the turbine or compressor housings. If the blades are damaged, the turbo is already destroyed. Look for metal that has come off the turbo in the intake tubes. Metal particles in this area may indicate a damaged engine.

Common Trouble Codes

Two typical diagnostic trouble codes for turbos include P0299 (underboost) and P0234 (overboost). If you’re receiving an underboost code, the issue could be a wastegate that’s stuck in the open position or a leak between the compressor and throttle. Causes of overboost, on the other hand, include a wastegate that’s stuck in the closed position, a wastegate vent solenoid that’s stuck in the vent position, or leaking or disconnected control hoses.

When diagnosing and repairing boost-related trouble codes, here’s a helpful repair tip to keep in mind: turbocharger operation can be affected by a dirty intake air temperature sensor. That’s because the dirty sensor is unable to pass temperature differences quickly enough. To fix the issue, remove the intake air temperature sensor from the intake manifold and clean it using either carburetor cleaner or bead blast.

Choose the Right Replacement

Once you’ve diagnosed your turbo and determined that you need a replacement unit, remember that NAPA® Echlin® offers both 100% new and quality-remanufactured turbochargers. Using extensive research to determine the numbers needed to compete in the turbo market, NAPA® Echlin® offers full-line coverage for import and domestic applications. NAPA® Echlin® also offer an array of related components, including turbo actuators, turbo oil drain tubes, and turbo speed sensors.