We often hear from customers who call saying their turbocharger has failed because it “isn’t creating boost” or “isn’t boosting” etc. In response, we have created these rules of turbocharger failure.
RULE #1 – No Boost Does NOT Mean a Failed Turbocharger
This may sound strange, but the turbocharger does not control boost. The turbocharger is nothing more than two fans connected by a shaft, and the fate of those fans is in the hands of other systems in the car. Most notably, the turbocharger actuator has the most control over the speed of the fans. Here is a VERY oversimplified map of what controls what:
Turbocharger = Controlled by Actuator
Actuator = Controlled by Vacuum
Vacuum = Modulated by Turbocharger Vacuum Solenoid (N75 valve on VWs)
Solenoid = Gets Vacuum from Vacuum System
Vacuum System = Gets vacuum from vacuum pump, check valves, etc.
RULE #2 – Airflow MATTERS!
A turbocharger will not create proper boost if there is an airflow restriction either on the intake or exhaust side. The turbo relies on high velocity airflow, so if there is a block somewhere the turbocharger won’t be able to create proper pressure. Most often, blockages from come clogged intake manifolds, failed airflow regulators or dirty catalytic converters.
RULE #3 – Don’t forget electronics
While the list above details the physical relations, don’t forget that most modern turbochargers are electronically regulated as well. Using a correct OBD diagnostic tool can gather information to help you figure out how your car’s turbocharger is being regulated.
RULE #4 – If you suspect turbocharger failure, STOP THE CAR!!!!!
As we’ve seen, a car merely not creating boost doesn’t mean the turbocharger has failed. When turbochargers DO fail, they will fail in a very dramatic fashion. A loud pop is typically heard, and the car will begin smoking VERY heavily – you may not be able to see the car behind you. This is due to engine oil getting into the motor, and when a turbo fails it will put engine oil into the intake system. Finally, the car may start running very rough and won’t have any power. STOP THE CAR!
It is vital to the health of the other components that you IMMEDIATELY stop the car, pull over and call a tow. DO NOT restart the car. Driving with a broken turbocharger will ruin your motor – the turbo may have broken into pieces that can enter the motor and damage the internals, or the turbo may be leaking so much oil that the car will run out of oil quickly or be overwhelmed and “hydrolock”. Both are very, very bad things.