Slight knock on OM606 turbo? - PeachParts Mercedes-Benz Forum

Parrot of Doom · #1 12-05-2006, 09:58 AM

I took the fuel filter off today, filled it with Redex injector cleaner which contains cleaning additives and a cetane booster.

Filled it to the brim, put the filter back on, and started her up. Everything runs fine, took it up the road and went for a spin, opened the engine right up and everything was sweet.

You can watch a mobile phone video of my engine here using quicktime

However there remains a nagging little bit of knocking that I can't seem to eliminate. You can only just hear it, its very faint, but if I put my finger on the 2 lines from the injector pump to the injectors of cylinders 1 and 2, I can feel the knock on one of them (the lower line of the two).

I wonder if somebody could do me a favour and see if they can feel a similar knock by putting their finger on each injector line?

I'm wondering if its worth buying the injector removal tool, pulling each injector out, and cleaning them out? What is the price of a new nozzle for these injectors (the MB system suggests you can buy all of these as service items)?

/edit: youtube version of video: http://www.youtube.com/watch?v=-9FLGsp7rdQ

scott19_68 · #2 12-05-2006, 09:04 PM

Mine sounds exactly the same and just assumed that's normal operation. I think a diesel purge helps a little bit - maybe that is worth a try before pulling the injectors?

nhdoc · #3 12-05-2006, 10:23 PM

Mine knocks a little too at idle...has since I have owned it. Sometimes it is worse than others and sometimes it is gone...I just have learned to accept it. I believe it is benign and for some reason normal. It's worse in cold weather on my car, BTW.

TMAllison · #4 12-05-2006, 10:27 PM

I think mine sounds much the same at idle; maybe mines a little quieter when it is goosed but may just be the sensitivity of the video mic I am hearing.

Many engines seem to expirience increased noise after doing delivery valves, not sure about nozzles. Unless the nozzles are fouled with carbon it is probably not necessary to replace them. A good cleaning, new shims and balanced pops would probably serve just as well. Other than the spring getting tired, which is brought back into spec with new shims, there is not much there to wear out.

scott19_68 · #5 12-06-2006, 09:13 AM

I've seen a tech. service bulletin (AF07.10-U-1800AG) that is titled "Knocking noise at idle through approx. 1500 RPM from area of fuel return line" that is supposedly applicable to most small MB diesel engines (60[1,2,3,6] & 61[5,6,7]). It references an expanded fuel return hose (008 997 64 82) to dampen pressure pulses from the fuel feed pump. I've seen this hose for sale on eBay but it does not look like it would be a drop in replacement for the feed hoses on a 606.

Have you heard of this? If all it does is disrupt the pressure pulses, maybe a small inline canister would work?

aklim · #6 12-06-2006, 09:48 AM

The question is whether the injectors need replacement. I took mine out and had them checked and one of them cleaned for $70 a few months ago. Makes the engine smoother and power seems better because of the 1 injector that had lower pop off pressure and bad spray pattern.

Parrot of Doom · #7 12-06-2006, 01:19 PM

I think that at nearly 180,000 imperial miles the injectors may well want cleaning. Trouble is that once you start thinking about these things, you want to remove and clean/service absolutely everything

I keep worrying about things like the water pump, its making no odd noises whatsoever but those plastic impellor blades.....