WE started seeing this problem about 2.5 years ago! MB says to use the later pre-chambers from the OM603.971 engine but you also need the newer injectors & pre-chamber lock rings(all of that costs almost $1000). AT our dealer we have the "NEW" head modified(machine shop) so that the old style prechamber will fit.

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MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
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190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
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