617 going bad? - PeachParts Mercedes-Benz Forum

airbus · #1 10-07-2008, 09:59 AM

I read a couple of posts about knocking 617s, so here's mine:

http://www.youtube.com/watch?v=Y1mEotCVSUg

This is the car I bought for $400, not even knowing if it was running. I did a compression test (320-300-340-300-320), adjusted the valves, had the injectors tested (all good) and I'm assuming that the diesel I bought at the local Gulf station is good. What do you think? Sounds like a rod bearing to me...

pawoSD · #2 10-07-2008, 10:06 AM

Sounds more like one or more injectors nailing, or maybe even timing chain slap. How bad is the stretch on the chain? I'd check all that stuff too before I condemned the engine....how many miles on it? Is it the one in your sig with 265k? Thats pretty low miles for a 617....

airbus · #3 10-07-2008, 10:15 AM

Believe it or not, the (used) engine has only 160k, installed by a MB dealership. I have the invoice. Everything I did (see previous post) did not change the sound at all. It is obvious, however, that the PO badly abused the car.
Timing chain stretch: How do I check this? Are there any other signs that would point there? There is nothing else unusual with this car, she runs just beautifully, lots of power and other than the knocking the engine is very smooth, oil pressure perfect, only little to moderate smoke (I opened the ALDA), etc...

Maxbumpo · #4 10-07-2008, 04:07 PM

Quote:

Originally Posted by airbus

Timing chain stretch: How do I check this? Are there any other signs that would point there?

See post #5 in this thread: http://mbca.cartama.net/showthread.php?t=24112

What are the signs that the engine/car was abused?

Timing chain stretch will give you an idea of how often the oil was changed. Using non-synthetic diesel-rated oil and changing at normal intervals of 5k miles, you should find 2 degrees or less of stretch assuming the engine has 160k miles.

An engine stethoscope would be really usefull to narrow down the location of the noise. There are more than a few external things (like air cleaner bracket broken, or totally collapsed engine mounts) that can make a lot of noise. On the OM60x engines, fossilized o-rings on the oil filter stem can cause the engine to make strange and alarming noises.

If you pull the injectors to look at the pre-chambers and check the condition of the pins, the seal rings are a one-time use item so stock up with new ones before you go that route.

If the noise is injector related, it may remain after the injector(s) is fixed because the carbon deposits in the pre-chambers are still there and will affect combustion noises until they are burned out.

Rocketrider · #5 10-07-2008, 10:25 AM

Just kidding, but my 83 300D sounds EXACTLY like that. I've posted on this problem before and was offered some great suggestions, but still no solution.

The sound isn't coming from the area of the timing chain. It is coming from the area of #3 cylinder and may include #2 or #4 as well. I don't remember. I was told the most likely cause was injector nailing. I had the injectors pop tested and cleaned/replaced the bad ones. While they were out, I rolled the engine over and the ticking was gone! I just knew that was going to fix it. Not so fast! Without compression, a rod bearing may or may not make the noise. It depends on how bad it is. I put the known good injectors back in and the noise was back. I hope not, but I really think it is bad rod bearings...for us both. Keep us posted and good luck!

Tim

coonerboy · #6 10-07-2008, 10:43 AM

Did you try a diesel purge? When running on the purge mine got significantly quieter. This way you might be able to isolate an injector problem from a rod/chain etc. problem.

kerry · #7 10-07-2008, 11:09 AM

Doesn't sound like a rod bearing to me. It's not a deep enough sound. I don't know what it is but it also sounds higher up in the engine than a rod bearing.

Rocketrider · #8 10-07-2008, 11:17 AM

It's quite possible that the sound you're hearing is the piston hitting the head. When the rod bearing goes, the piston has a longer stroke. Therefore, the sound you hear is higher up in the engine than a rod bearing. I certainly wouldn't drive it. If that's what it is, you could ruin your head as well. I hope I'm wrong, since I have the same issue.

Quote:

Originally Posted by kerry

Doesn't sound like a rod bearing to me. It's not a deep enough sound. I don't know what it is but it also sounds higher up in the engine than a rod bearing.

airbus · #9 10-07-2008, 11:45 AM

Quote:

Originally Posted by coonerboy

Did you try a diesel purge? When running on the purge mine got significantly quieter. This way you might be able to isolate an injector problem from a rod/chain etc. problem.

I ran it on MMO, no difference.

The sound is louder underneath than on top. It's loud when you start the engine and quiets down immediately. It gets louder when the engine is warm and it really hammers when accelerating. It's definitely mechanical, the question is, should I drive it until it dies (hey, it was only 400 bucks...) or should I attempt to fix it. Is it possible to remove the upper oil pan and get to the bearings with the engine in place?

Alastair · #10 10-07-2008, 11:52 AM

Whats the idle-oil pressure when hot...?

barry123400 · #11 10-07-2008, 12:17 PM

Just my two cents. Post your rate of fuel consumption. This information can sometimes indicate what might be causing the knocks that never seem to get worse. Low milage combined with the knocking could for example be pre njection by one injector. Not too likely but sound blurbs on the site are not usually difinitive. Too many variables. Also what I have mentioned is a long shot.

One gentleman posted very high milage with a knock for example. This knock never worsened. Unless piston slap that should have istill ncreased over that many miles and the sound would be worse in my opinion. What was wrong? It would not Have been a rod bearing for example in my opinion either. It could not have gone the distance in my opinion.

airbus · #12 10-07-2008, 01:49 PM

Oil pressure at idle is 2 bar. I just bought the car, I haven't driven it far, yet. Maybe 200 miles or so, but I will be driving it through the winter. Let's see what happens...

winmutt · #13 10-07-2008, 03:42 PM

Did you inspect the prechambers?

Egads I just heard the video. Pull your injectors and inspect all the prechambers and DO NOT run the engine.

winmutt · #14 10-07-2008, 04:53 PM

Did cracking the injector lines one at a time point to a specific cylinder?

airbus · #15 10-08-2008, 12:57 AM

Quote:

Originally Posted by winmutt

Did cracking the injector lines one at a time point to a specific cylinder?

Nope, I did all the "easy" stuff. Nothing changed that noise. However, I looked for metal pieces during the first oil change, couldn't find any. That is probably due to the fact that the PO had the oil pan off already and removed them. He then used that blue silicon ***** to seal it. (I guess that answers Maxbumpo's question about the abuse, too).

WTF, now I really don't know what to do. I can't rebuild that engine, no garage, no money, no time.