1. Something isn’t leakproof — fault source #1
Leak on the charge air side:
If a turbocharger is replaced after thousands of kilometers, the charge air pipes connected to it must also be removed or decoupled during the repair. The flanges normally contain sealing rings, which have been pressed into position over many years. If you open the joints and then put them back together again, this old, deformed seal becomes unusable. The charge air escapes, resulting in whistling and hissing. However, a stone chip in the charge air cooler will also manifest itself in this way. And the escaping boost pressure also reduces the vehicle’s power output.
Leak on the exhaust side:
The exhaust gases leave the engine at a very high speed and several bars of pressure.
If a used metal gasket is reused—e.g., on the manifold flange—exhaust gases can easily escape at this point. But even the best gasket is of little use if the flange areas are warped or heavily clogged. In the case of bigger leaks, power losses may occur, as insufficient exhaust gas arrives at the turbocharger’s turbine. As a result, the boost pressure falls.
2. Blockbuster: how to prevent blockages
If the turbocharger gets too little air, it will start making noises. If, for example, the air filter is not checked thoroughly and replaced regularly, the intake resistance increases substantially. In the worst case, the rotor assembly shifts axially, causing the impeller to brush against the housing—a phenomenon you can’t fail to hear!
It’s exactly the same on the other side: if the exhaust gases accumulate here and cannot flow freely out of the cylinder, disturbing flow noises will soon be produced ( see TM 03/2016). Incorrectly mounted gaskets can also cause a bottleneck in the exhaust gas system.
3. Ringing alarm bells: foreign objects in the turbocharger
A foreign object in the turbocharger—and it’s already ringing in your ears! On the exhaust side, pieces of the manifold that have broken off can grind against the turbine wheel. This causes an imbalance in the rotor assembly, the shaft breaks, and the turbocharger suffers a total failure!
Of course, foreign objects also lead to serious problems on the compressor side. Whether it’s loose nuts from previous damage ( see TM 07/2016) or other objects that hit the impeller, damage is inevitable!
Even if the vanes of the compressor are “only” bent, this can still cause significant flow noises during operation.