Bad News...Serious knocking sound on 95 E300d - PeachParts Mercedes-Benz Forum

Greg300sd · #1 01-16-2006, 12:07 PM

So it started with a faint knocking sound just above the normal diesel clatter. This is the OM606, 95 E300D, 161K. I've only had it about 6 months. At first I thought sticky valve, but after reading previous posts and talking with other people I think I have a serious problem. It's really, really loud and moves with the rpm of the engine. It is constant, ie. startup, after warm up, idle, under load, etc. How painful is it going to be to keep this car now $$$$ ????

Just venting a bit...it's a real downer....I'll stop wallowing in this shortly. Good day.

Matt L · #2 01-16-2006, 12:26 PM

It could be a bad injector or delivery valve in the IP. Unfortunately, it's rather difficult to loosen the injector lines while running that engine, as this is the easiest way to diagnose this in the older engines.

Greg300sd · #3 01-16-2006, 01:29 PM

sound really loud?...I'm talking clearly above the normal engine noise. Sound as though it's at the front of the engine??? It was initially soft but above the normal engine sound...Now..WOW...it's loud. Like someone hitting the block with a ball peen hammer. I should mention that I have at least one bad glow plug. I wonder if operating with a bad glow plug could lead to injector problems???

DieselAddict · #4 01-16-2006, 02:04 PM

I'd run some Diesel Purge through the system. If anything it will tell you whether it's a combustion knock or a mechanical knock. Hopefully it's the former.

Hatterasguy · #5 01-16-2006, 04:55 PM

As your the engine is running crack the injector lines one at a time and see if the sound goes away. I have done this before on a 606 its cake.

If you crack a line and it goes away you have found the bad cylinder or more probably a bad injector. Swap that injector with another one and see if the sound follows that injector.

btw you need a special socket to pull the injectors on a 606. They are not expensive about $30 last I checked.

Rich300TDMBZ · #6 01-16-2006, 05:05 PM

Mine was knocking like that last summer. It was a clear "tock tock" noise, but it seemed to lessen after I drove the engine hard - that is, above 65 mph on the highway). In the summer, the price of diesel went up above $3, and I changed to SVO (Soy bean oil from Costco). I ran about 4 tanks of this, but changed back to dino when the price dropped. In between, the noise just disappeared

Greg300sd · #7 01-16-2006, 08:55 PM

HatterasGuy,
I would guess gaining access to the fuel lines requires removal of the intake eh? I'll get on it and crack those lines one at a time...possibly this weekend. I thought of draining the oil and filtering it somehow to check for metal shavings, etc....wouldn't that indicate a rod knock condition? I'll post again after testing. Thanks to all for the input. I can't believe as loud as this is that it would be an injector...I hope it's that simple. I have no history with this so I'll work on it.

tenknots · #8 01-16-2006, 09:03 PM

This type of noise is not uncommon on diesels. I've heard it sound just like someone was taking a hammer to the block. The odds are good it's just a bad injector.

Good luck.

POS · #9 01-16-2006, 09:32 PM

Sell it to me! I'll give you a $1000!

Don't worry about it; get it diagnosed, then freak out.

mdisav · #10 01-16-2006, 10:00 PM

I had a 96 E300 DIESEL. I had sold the car. The night before the guy came to pick it up I warmed it up and cleared off the snow. Then I took it for one last ride before it was a goner. I got on it and really reved it up. When I got back it was idling funny and sound like it was going to throw a rod. I mean it was loud. I checked the oil and it was fine. I decided to hop back in it and go for another ride. The noise did not go away when the rpms increased and it was really loud. I turned the corner and just mashed the pedal to the floor. The noise got really loud and when it reached 4500rpm or so it disappeared and never came back.

I believe it was a piece of carbon or egr/oil goop that got sucked in and bounced around in one of the combustion chambers until it got pushed out during hard acceleration.

So go give it a good italian tune up and see what happens.

Hatterasguy · #11 01-17-2006, 11:52 AM

Oh wait this is a na 606, then yeah the intake has got to come off. I am used to the turbo charged one.

Don't worry these are 606's they are extremly tough, unless you never changed the oil, the bottom end is fine. I don't care how many times you redline it these are tough motors.

TX76513 · #12 01-17-2006, 11:54 AM

Quote:

Originally Posted by mdisav

I had a 96 E300 DIESEL. I had sold the car. The night before the guy came to pick it up I warmed it up and cleared off the snow. Then I took it for one last ride before it was a goner. I got on it and really reved it up. When I got back it was idling funny and sound like it was going to throw a rod. I mean it was loud. I checked the oil and it was fine. I decided to hop back in it and go for another ride. The noise did not go away when the rpms increased and it was really loud. I turned the corner and just mashed the pedal to the floor. The noise got really loud and when it reached 4500rpm or so it disappeared and never came back.

I believe it was a piece of carbon or egr/oil goop that got sucked in and bounced around in one of the combustion chambers until it got pushed out during hard acceleration.

So go give it a good italian tune up and see what happens.

No offense but that's putting a lot of confidence on the carbon theory

mdisav · #13 01-17-2006, 12:40 PM

They are known to be quite robust. Look what Mauri has done to his 606 with a super turbo. I believe he has not done anything to the bottom end but I may be wrong. Has anyone had one of these motors fly apart yet?

tony1963 · #14 01-17-2006, 09:31 PM

You've likely got a bad fuel injector. I have my 95 E300 down for repairs right now because I had some glow plugs frozen in the cylinder head.

I have all of the tools to change everything on that engine. Bought it all.

My suggestion is to change all injectors and all glow plugs. I have a good source for Bosch injectors and glow plugs.

e-mail me at tony1963tony@excite.com

Greg300sd · #15 01-22-2006, 09:44 PM

I bought a mechanic's stethoscope and have some interesting information:

1. The metallic knocking sound seems the loudest when I position the stethoscope on the vacuum pump housing.

2. It is loud when placed on the valve cover end closest to the radiator but still not as loud as the vacuum pump cover.

More background:
This started as a soft ticking and then got louder.
More importantly another symptom I've noticed is that the engine no longer comes to an abrupt stop when I turn it off with the key(what I would previously call normal). It kind of "dribbles" down to a stop.

The engine idles normal and visibly it's not shaking or rocking side to side..all looks normal except for the knocking noise.
As of this weekend the noise is not as loud as it was previously.
Oil quantity and pressure are normal when the engine is running.

**************
So the question is can a vacuum pump going south make this type of noise.
**************

It's a rythmic metallic knocking that increases and decreases with rpm's and does not skip. I think I'm narrowing this down to an injector or vacuum pump problem. Any ideas??? Especially about the possiblity of the vacuum pump being able to generate this type of noise. I think I may order the gasket and take it off and check it first.