W124 300d (diesel)

[TOPMERCS]

Firstly kindly excuse me if this is the wrong section for this, thanks, now to the question - kindly help - a mate of mine owns the w124 300 diesel, has noticed , especially in the extreme heat, while driving in traffic for appx. 20-30 minutes and has got the car on idling, he has noticed a slight change of noise from the engine (he thinks), sounds like rattly / clonky, once the engine
is revved or driven, noise disappears, the funny thing is when driven in the evening when temperature is fallen, it doesn't happen - also the oil pressure gauge operates normally (like it usually does).,also the temp gauge works normally. Is there anyone who could kindly advise what it could be, although someone told him there is nothing to worry as that is normal, is this true??.

Your advise and suggestions is much appreciated, thanks.

 

[Dieselman]

It could be the EGR making a bit of a resonating noise but is probably a slightly sqiffy squirting injector. This is normally most noticeable at idle due to the very low fuel delivery.
Try running a good dose of injector cleaner through the fuel system.

A test is to crack off each of the injector lines individually. If the noise stops then that's the dodgy injector.

In all seriousness it's probably not worth bothering about.

 

[TOPMERCS]

THANKS FOR THE RESPOND,I asked the Merc specialist and he said do not worry, as in this intense heat and being held in traffic, it sounds like thinning of the oil.He said not to worry about it.?? - although what do you guys think, could this be true and if so isnt it a bad thing for the thinning of the oil???, Oil in his car is changed appx. every 5000 miles and the injectors have already been replaced.