I have a friend who has a 300E /1991 and this morning he called me to find out why his engine has a knocking noise when cold and it goes away when it warms up?Any ideas ??
His car has 140000miles and and otherwise seems fine.

His description is like a rod or bearing,Anybody experiance this.He bought the car in the summer.
Thanks

Mine did this off and on for the whole winter. I think that when the engines get some miles on them, they will have some carbon deposits. When they sit, the pistions can come into contact with outside air if that exhaust valve is open. The carbon can then release from the piston because of drying out and then it will knock for a minute or two...

JUST MY THEORY