Any help with this is very much appreciated! I havea 2004 CLK 500. Just recently I got an alert telling me to check my coolant level. Of course asa woman if the light goes off there's probably nothing to worry about so I didn't think twice about it. It came on a couple more times with me procrastinating and saying I'll check it tomorrow. This has been going on for about a week. Now all of a sudden the check engine light is on and I have a knocking sound once I start it up. I figured maybe it was the oil so I put some in. The knocking is still there. I haven't been driving it at all since the knocking started. A little worried that I'm going to mess it up even more. If someone has any experience with this I would appreciate your help very much. I just like to sound a little knowledgable when I go to the service center sothe don't end up sticking it to me so to speak. Thanks again!!!

 

What type of knocking noise? Is it only at start up or is it constant.? does the noise come into play all the time or on deceleration or acceleration. Depending on what the answers are maybe I can help.