FAULT DIAGNOSIS – INSPECTION GUIDELINES

(This chapter is meant for standard or upgrade applications, only some points are                         applicable for Truck- and Tractorpulling applications)

Very often fully functioning turbochargers are replaced, because the problem shows up at the turbo, although the turbocharger is in good condition.

Before ‘blaming’ the turbocharger, carefully read following information and try to identify the most probable ‘cause’ of the problem.

As a general rule, if both the Radial- and Axial clearances are within tolerances and there is no ‘visual’ damage to both compressor- or turbine wheel, it is most of the time very unlikely, that the turbocharger is faulty and causing the problem observed.

ENGINE SMOKING

Smoking may be due to air intake restriction, often caused by a dirty/partially blocked air filter or a collapsed intake hose. These problems affect the air/fuel ratio and give black smoke. Also if the engine cannot breathe as designed, it will pull air from other sources. Excessive closed crankcase ventilation will give smoke.

LOW ENGINE POWER / LOW BOOST PRESSURE

Air inlet restriction prevents the engine from breathing as designed, this increases the engine operating temperature. As an air leak in the compressor outlet, or a partially or blocked intercooler would restrict the engine breathing.

NOISY / WHISTLING TURBOCHARGER

Often the noise comes from air/gas leakage, due to pre-turbine exhaust gas or an air/boost leak. Check all joints, if noise continues check turbocharger clearances and wheels for housing contact.

SEIZED WHEELS / SLUGGISH TURBO

If the turbocharger rotor has seized or is hard to rotate, this is often due to lubricating oil degradation which can cause a high build up of carbon in the bearing housing interior, restricting rotation. Insufficient or an intermittent drop in oil pressure can cause the rotor to seize, as can introducing dirt into the lubricating oil.

WORN / EXCESSIVE CLEARANCE

A turbocharger has specific axial and radial rotor clearances. These are sometimes misdiagnosed as ‘worn bearings’. If the clearances are out of specifications, the cause could be attributed to a lubricating oil problem, insufficient oil, dirt ingress, oil contamination with engine coolant or fuel.

OIL LEAKAGES

Oil leakages at the turbo, provided bearing clearances are normal, are in most cases a result of an engine problem. Check crankcase pressure, carter ventilation, air filter.