Recently I have been hearing reports of broken timing guides from owners of M177 C63 and GLC63. These manifest with a tek tek tek sound that goes away after several minutes. Fixing the issue is approximately 8k from a dealer and 4k from an indy. If you let this go the car will have long starts and begin to sound horrible with a clear loose chain sound.
PTG markets a timing guide replacement set which you can buy from us or directly from PTG. This set is approximately $1700 and includes tensioners and new chains. If you are retiming an engine you may also want to put in a new water pump. This of course is slightly beyond the repair needed, but if you are dropping the engine anyway it may make sense to do everything.
This is what the engine will sound like if the issue is unfixed.
