Audi A6 2.4 coolant leak - not to find anywhere

SOURCE: speedometer and odometer not working 92 audi 100

I had similar problems with speedos in two 1990 Audi 100s, it was some time ago, but the contacts on the circuit boards on the back of the speedo deteriorate and do not give a good contact. I bought second hand speedos, only to find they had similar problems, eventually it was very easy to fix, I shaved matchsticks to chisel points and pushed them into the circuit boards to add pressure on the contacts and improve connection. After that repair drove the cars for a few years and the problem did not recur. It was a long time ago and I cannot remember exactly where the matchsticks were placed but look for soldered points near the edges of the boards. Regards, Michael

SOURCE: coolant leak into oil

head gasket!

SOURCE: I Just Bought A 1990 Audi V8 Quattro. I Changed The Oil And

YOUR OIL PRESSURE SWITCH IS DEFECTIVE

SOURCE: 2000 Audi A4 quattro with abrupt gear shifting & low oil pressure

I hope that you had the proper weight oil installed, at your oil change. If your oil is up to the proper level, and it's rattling ,this is VERY bad. White smoke usually means steam in the exhaust, and that means a blown head gasket. Check your coolant level. I wouldn't drive it anymore......until someone knowledgeable can diagnose it!!!!!

SOURCE: 1998 Audi A4 Quattro Engine Noise

the timing is too far advanced at the time of the noise, the "diesel knock" is detonation

or this could be from using fuel with a low octane rating, try premium or octane booster.

or may have carbon build up in the conbustion chamber causing fuel to ingnite while entering cylinder