Welcome to this year’s MPULSE Christmas challenge! For the whole of December you’ll be able to show off your knowledge and pick up prizes.

We want to get you involved in the run-up to Christmas and have looked out a few tricky damage scenarios for the next few weeks. With any of them, you could win a MAHLE technical package (contents: MAHLE damage brochure and technical poster) as well as a handy tool for the workshop.

And for a Christmas treat, we’ll give you a full explanation of our damage scenarios and tell you how to avoid them on December 19.


Send us an e-mail containing the subject “merry mpulse” and the correct answer (e.g., photo 1, answer c) to Or follow us on Instagram and respond under the relevant post with #merrympulse and the correct answer (a, b, or c).


Photo 1


Question: A piece is missing from the valve disk of the exhaust valve. What happened?

#Valve #Exhaustvalve #Melting #MPULSE


a) Increased wear and tear due to leaky air filter

b) Valve spring too strong

c) Inadequate valve clearance

Solution Photo 1

c) If the valve clearance is too low, the valve can no longer close completely. This prevents the heat from being transferred to the cylinder head via the valve seat. As a result, the valve plate overheats and burns out.

Photo 2


Question: The turbocharger’s impeller has broken apart in the middle. What happened?

#Turbocharger #Impeller #Fracture #MPULSE


a) Excessive exhaust temperature

b) Maximum speed exceeded

c) Inadequate lubrication

Solution Photo 2

b) The turbocharger has exceeded its maximum permissible speed. Due to the high centrifugal forces, the compressor begins to deform plastically. So much so that the aluminium begins to flow and as a result the compressor wheel tears apart in the middle. This can happen if, for example, the wastegate is jammed, the adjustment of the VTG (Variable Turbine Geometry) has been changed or if a diesel "passes through" and no speed regulation takes place (self-running).

Photo 3

Starter motor flange broken

Question: The starter motor flange is broken. How could this happen?

#Startermotor #Broken #MPULSE


a) Battery too powerful, starter motor was overloaded

b) Motor was still in motion when started

c) Pilot bearing seized, flange ripped off

Solution Photo 3

b) The engine was still moving during the starting process. However not forwards but backwards. This happens, for example, with larger construction machines when the engine is started again immediately after shutdown. If the starter starts up at the moment when the engine is swinging against the direction of rotation, the bell is broken by the enormous forces.

Photo 4


Question: Small dots can be seen on the rotor shaft of the turbocharger. What happened?

#Turbocharger #Rotor #MPULSE


a) Engine switched off while hot

b) Intake air temperature too high

c) Too much strain put on engine while cold

Solution Photo 4

a) If the engine has not cooled sufficiently before switching off, the accumulated heat from the turbocharger can no longer be removed. This can cause the engine oil to boil at the bearings in the turbo. It burns in the radial bearings on the rotor shaft and leaves these traces on the shaft.

Photo 5


Question: The piston is melted at the skirt and crown. What happened?


a) Extreme wear and tear due to defective air filter

b) Poor quality fuel

c) Defective crankcase ventilation


  • The competition starts on December 3, 2018, and ends at midnight (CET) on December 19, 2018.
  • Each participant may take part in the competition only once for each damage scenario by posting the correct answer under the relevant damage scenario on Instagram using the hashtag #merrympulse or by sending the correct answer (e.g., photo 1, answer c) by e-mail to with the subject “merry mpulse.”
  • Participation is open to all natural persons.
  • Each participant agrees not to share any illegal content.
  • All personally identifiable information will be treated as confidential and will not be disclosed to third parties.
  • This excludes service providers domiciled in Germany and who provide assistance in the implementation of this promotion (“contracted data processors,” “shipping providers”).
  • The following terms and conditions of participation [PDF; 386 KB] also apply (only german). Our general Data Protection Policy applies.


We regularly provide technical tips relating to the powertrain, thermal management, and mechatronics in automobiles.


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