My 2001 e320 has a knocking from the engine. The knocking speeds up when accelerating. I have checked oil level, which is fine. Also had an oil change 2 months ago with no initial signs of knocking, leading me to believe it is not from oil or filter. I did have a catalytic converter installed recently. Any suggestions?

 

Present in P and N too? How about with the tension off the serp belt so no accessories are turning?

 

Yes, it does still knock when in P and N. I have not tried taking tension off serp belt. Wouldn't know how to do that.

 

Present in P & N basically rules out driveline/flex disks, etc. Removing belt (and running 30 secs only - no waterprump) confirms whether or not noise is accessory related.

Realistically, it doesn't sound like you will be the one to repair it if pulling the belt is difficult. Should prob let a mechanic hear and diagnose it.

 

You said that recently had a catalytic converter installed............try checking to see if they my have bent the pipe and now its tapping the under carriage?? ………won’t hurt to look!

That’s the only thing that has changed, and has not been looked at!

Good luck to ya!

 

Thanks. I will check to see if the pipe is bent. From what I understood, lifters tend to quiet after running for awhile? This tapping/knock does not go away, even after running for hours. Also does not go away with higher speeds. Never thought to check the pipe. I will do that. Thanks again!

 

Could it be the valve lash needs to be adjusted?

 

Valve noise would be like a tap not a knock. With a knock if the frequency increases with the rpm it is likely to be a main or rod bearing. This is unusual unless the car has extremely high mileage and you did not mention the miles. In any case this ciuld be quite serious and should be looked at by a dealer or other experienced party BEFORE the car is driven any further. If you continue to run the car there is the distinct possibilty that it will let go damaging the block and that means an entire new engine with no core allowance while if it is not too late the engine could be salvaged.

 

It actually does sound more like a tapping. The car has 110,000 miles. Find it very odd that the sound occurred after having a new catalytic converter installed. Plan on checking the pipes, just curious if it could be valve related. It is a constant tapping. Very annoying.

 

Im actually going through that right now. the E420 has 181k and its been like this for a while now... But thank you! IM driving it to HMS right after work and using another car till its fixed.

 

the E420 "tick tick tick" is due to the infamous m119's plastic oil guides that pop off from poor oil change intervals or after wear and tear over the mileage, DIY is on mercedes wiki: http://www.mercedesshop.com/Wikka/M119OilGuides
that DIY applies to the m119 (4.2 liter V8 as well) with the parts from autohauz and the time to DIY you can save thousands with this DIY compared to dealer or indy doing this
I will be doing this soon..