Test equipment for fresh air, intake, and charge air systems

Frequently Asked Questions About the Diagnosis of Intake, Fresh Air, and Charge Air Systems

Problems in the intake and charge air systems can cause symptoms similar to those of a faulty turbocharger, sensor, or engine control system malfunction. A mechanical pressure and leak test therefore helps identify leaks and pressure losses independently of electronic diagnostic readings. Here, we answer common questions about diagnosing intake, fresh air, and charge air systems.

• What are the components of the intake and charge air system?

  The exact configuration depends on the engine design.

  In a turbocharged internal combustion engine, this may include, among other things:

  • Air filter and air intake system
  • Intake manifolds and hoses
  • Turbocharger or compressor side
  • Intercooler lines
  • Intercooler
  • Plug-in and hose connections
  • Throttle or control components
  • Intake manifold

  A leak at any of these points can affect the airflow or the built-up boost pressure.

• What is the difference between intake air and charge air?

  The term “intake air” generally refers to the fresh air supplied to the engine.
  
  In a turbocharged engine, this air is compressed by the turbocharger or supercharger. The air downstream of the supercharger is typically referred to as “charge air.”
  
  The charge air is often passed through an intercooler before it is fed into the engine.

• What is an intercooler system?

  The intercooler system delivers the air compressed by the turbocharger to the engine.

  Depending on the vehicle, this system includes, among other things:

  • Intercooler hoses
  • Pipes
  • Fittings
  • Intercooler
  • Connection points
  • Other components between the turbocharger and the engine

  This system must be sufficiently airtight during operation.

• What symptoms can a leaky intercooler system cause?

  Possible indications may include, for example:

  • Loss of power
  • Insufficient boost pressure
  • Discrepancy between target and actual boost pressure
  • Delayed response
  • Unusual noises
  • Troubleshooting codes related to boost pressure control
  • Unusual engine behavior under load

  However, these symptoms are not definitive. Therefore, the system should be inspected thoroughly.

• Can a leaky intercooler hose act like a faulty turbocharger?

  Yes.

  If air compressed by the turbocharger escapes before reaching the engine, the intended boost pressure cannot be achieved.

  This can cause symptoms similar to those of a problem with the turbocharger or its control system.

  Therefore, the integrity of the charge air system should be checked before replacing the turbocharger.

  Turbocharger test and diagnostic tools are available for further diagnosis.

• How can a charge air system be checked for leaks?

  The system—or a defined section of it—is sealed off and pressurized using a suitable testing device.
  
  The system is then monitored to determine whether the pressure is maintained or whether a leak can be located.
  
  Special leak testers for intake and charge air systems are available for this purpose. The current Leitenberger MLPS systems are equipped with pressure gauges and overpressure protection to ensure a controlled test setup.

• Can an electronic diagnostic tool replace an intercooler leak test?

  Not entirely.

  Electronic vehicle diagnostics can, for example:

  • display error codes
  • intercooler pressure sensor readings
  • air mass readings
  • setpoint/actual values
  • control information.

  A mechanical leak test, on the other hand, directly answers the question of whether the tested intercooler line is actually leak-free.

  Both diagnostic methods complement each other.

• Why is a loss of pressure in the charge air system a problem?

  If compressed air escapes from the intercooler system, the engine will not receive the intended air volume or pressure.
  
  The engine control system and boost pressure control can respond accordingly.
  
  The specific effects depend on the engine, the control strategy, and the size of the leak.

• Where do leaks in the intercooler system commonly occur?

  As a general rule, particular attention should be paid to connection and transition points.

  These include, for example:

  • Hose connections
  • Snap-fit and push-to-connect systems
  • Gaskets
  • Pipe transitions
  • Intercoolers
  • Connections to the turbocharger and engine

  The actual leak must be located on the specific vehicle.

• Could the intercooler also be leaking?

  Yes.
  
  In applicable vehicles, the intercooler is part of the pressurized charge air system and can therefore also be a potential source of a leak.
  
  A pressure test of the appropriate section of the system can help with troubleshooting.

• Is it necessary to always use the maximum possible pressure during testing?

  No.

  The permissible test pressure depends on the vehicle, the system, and the manufacturer’s specifications.

  The maximum output pressure of a test device is not a universal target test pressure for every vehicle.

  For example, the current Leitenberger MLPS test systems are equipped with a safety valve that has a maximum output of 1 bar; nevertheless, the test pressure permitted for the vehicle must be observed.

• What should be checked if the intercooler system is airtight but boost pressure problems persist?

  The diagnosis should then be expanded to include adjacent systems.

  Depending on the fault symptoms, the following may be considered, among others:

  • Turbocharger
  • Pneumatic or electronic boost pressure control
  • Sensors
  • Exhaust back pressure
  • Air mass measurement
  • Intake side before the turbocharger
  • Crankcase ventilation

  Test and diagnostic equipment for turbochargers as well as crankcase pressure gauges for blow-by gases can be used for this purpose.