300SDL engine noise
 

Hi,
I am a recently new owner of a 86 300SDL. Just the other day, I noticed that it has a knocking/rapping sound comming from what seems like one of the injectors. Can that be the case, or is it a camshaft /tappet issue? The car has not got much mileage on it and spends most of it's time sitting. any Ideas as to what to start looking at to trouble shoot this issue?

Also I would like to get some of the manuals for the car, would love suggestions as to where I might find them?
Thanks
Jason

This is a tough one to diagnose long distance. Injector knock is certainly not unheard of in these diesels, and the OM603 is known for a bit of lifter clatter. Try holding onto each of the six hard injector lines while the engine is running - you may be able to feel an injector knock.

Treatment is typically to acquire a bottle of Diesel Purge and run it through the engine. It's pretty impressive stuff. I know Performance Products sells it, not sure aboug Fastlane or Partshop here.

Lifter noise on these engines can generally be quieted down by using a good synthetic engine oil. I've run both Mobil Delvac 1 and Mobil 1 in mine; both have done a fine job.

- JimY

Take it one step further and crack the injector lines one at a time to see if you can isolate the noise to one cylinder.

There's a host of things that will help from what Jim suggested to replacing the delivery valve seals.

Sixto
95 S420
87 300SDL

Thanks guys. I will start with your suggestions next weekend and see where that leads me to. May be draining the fuel tank will help encourage the diesel purge to do it's stuff.
I will post more information as I learn and isolate some bits. If it is the injectors, or lifters, will I be doing harm by driving the car?
Jason

It won't hurt to drive it unless it's rod knock instead of injector knock.

Another thing to check is the belt tensioner shock. The rubber in the mounts goes, and it clanks just like a bad injector. Just take a screwdriver and push sideways on it while the engine is running. If the noise stops, get a new shock and install it (you must remove the visco clutch to get the lower bolt out).

Lifter noise is usually a result of not changing the o-rings on the center "bolt" of the oil filter cover. Replace them and use synthetic oil, and the noise will usually go away. Otherwise, you will have to isolate the problem one or ones and replace them (requires cam removal).

Peter

Peter,
I am adding your suggestions to the list. Thank you. Getting excited to have a look in the engine room, with a plan!
Jason

Purge
 

Do a search! Do not add Diesel Purge to the tank!. This is a waste. It is meant to run straigt from the can or a jar. So you need to unhook the supply and return lines and run them into a can of Diesel Purge. This way you are running all of it through at full strength and allowing it to do its job.

Alan,
I am planning on doing more investigating into the cause before attempting to fix any problem. In any event, your post reminds me of a diagram about how to use diesel purge. If it is needed, I will do as you suggest. Thanks
Jason