mbclk550

Hello everyone i wanted to know if anyone can tell me the problem to the knocking noise on startup. most of the time i turn it on even when it is already warmed up it makes some knocking sound during start up does anyone have a solution for this or what i can do to fix it thank you for your time.

number_one_c55

Very good question. I would take it to your local dealer. Ask to speak with the service manager as well as the master tech. If your not able to bring in the vehicle - at least take a sound recording with a decent microphone - one that is clear and easy to hear. If the dealer isn't of any assistance post it on line for others on here to hear and we will do out best to diagnose the problem for you. There are so many variations of what the issue could be.

400HP55

You have to be more specific. Is it a knocking or a ticking or a thud sound? How long does it last? When was the last time you changed the oil?

essagreb

I sometimes have the same issue.
During the (short) starter operation, only when the car is warm, and not every time, i can hear one knock noise.
I've to add that it occurs 1/10 of the start ups.