troubleshooting & diagnostic guide:

Our turbocharger diagnostic and troubleshooting guide is designed to give technicians the clarity and confidence they need before turning a single bolt. By walking through critical pre-installation checks, root-cause diagnostics, and best-practice procedures, we help eliminate guesswork and reduce the risk of costly comebacks.

TurboFAQ is a proven resource that protects performance, safeguards warranty, and ensures every turbo installation is done right the first time.

To figure out if your turbocharger needs to be replaced, follow these steps first to properly diagnose it:

Inspecting the rotating assembly:

  • Inspect the compressor and turbine wheel for contact with the housing.

  • Push the wheel radially towards the housing - the wheel should never be able to scrape the housing.

  • Axial play should feel like zero.

  • If the rotating assembly is scraping the housing, the bearings are likely damaged, and the turbo must be replaced.

  • Ensure clean oil is being fed to the turbo see install video, priming.

What are the symptoms of failed bearings due to a lubrication issue?

Check for the following symptoms of bearing failure:

COMPRESSOR CONTACT WITH HOUSING

1

TURBINE CONTACT WITH HOUSING

2

COMPRESSOR NUT COMES OFF DUE TO A SUDDEN STOP

3

how can i ENSURe my VGT is FUNCTIONing properly?

Below you will find some ways that you can verify that your VGT Turbocharger is functioning normally:

  • The VGT lever should move freely between the end stops. If the VGT lever feels sticky or seized, the turbocharger should be replaced.

  • The VGT may have been damaged by carbon or metal passing through the exhaust. Check the EGR cooler, injectors, and pistons/rings, and valves. Check for carbon deposits in the EGR or cylinder. If an engine produces a lot of soot, it may damage the VGT.

    • If your VGT is sticking, it could be because of:

      • Foreign Object Impact Damage (F.O.I.D.)

      • Engine Issues

      • Injector Issues

      • Carbon Buildup

      • Oily Residue Buildup

what do i do if my turbocharger is leaking oil?

If oil is leaking from the turbocharger, this does NOT necessarily mean the turbo has failed.

If the turbo spins freely, VGT function is OK, and the turbo still leaks oil - there may be an underlying cause.

Check for the following before assuming it has failed:

  • Inspect the rotating assembly.

  • Ensure VGT Function.

please note:

If the cause of oil leaking is corrected quickly, no damage will have occurred to the turbo — the turbo can remain on the vehicle.

what are some Causes of turbocharger oil leaks?

Check for the following causes of turbo oil leaks to see if your turbocharger can remain on the vehicle:

EXTENDED IDLE TIME, ESPECIALLY WHEN COLD

1

RESTRICTED AIR FILTER

2

HIGH CRANKCASE PRESSURE (INSPECT FOR BLOWBY + CRANKCASE VENTILATION FILTER)

3

BOOST LEAK

4

PLUGGED DPF

5

EXHAUST LEAK

6

COLLAPSING INTAKE CONNECTOR OR ELBOW

7

WHAT should I DO IF suspect I HAVE LOW POWER OR BOOST?

Take the following steps to check for potential problems:

  • Inspect the rotating assembly.

  • Ensure VGT Function.

what are some Causes of low power or boost?

EGR STUCK OR MALFUNCTIONS

1

BOOST LEAK

2

INTAKE RESTRICTION

3

MAP SENSOR CLOGGED OR FAILING

4

Why is turbo housing cracked or leaking exhaust?

OVER-TEMPERATURE EXHAUST

What causes over-temperature exhaust?

CLOGGED DPF OR DOC

1

FUELING ISSUE (SUCH AS MODIFIED, TUNED, DELETED ENGINES)

2

CHECK FOR LEAKY INJECTORS

3

CHECK FOR EXHAUST AND INTAKE RESTRICTIONS

4

CHECK FOR IMPROPER TUNING

5

please note:

Aggressive tuning or extreme conditions may cause excessive temperatures and damage the turbocharger.

What caused my compressor damage?

Inspect the leading edge of the compressor. If an object or debris is being sucked into the turbocharger it may cause any of the symptoms listed above.

If there is damage to the leading edge of the compressor wheel, your turbocharger has experienced F.O.I.D.

Here is what it would look like: