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...

Rocketrider · #4 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 · #5 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 · #6 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 · #7 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.

pawoSD · #8 10-07-2008, 11:42 AM

Could it be a bad/knocking vacuum pump? Or perhaps something else on the engine is rattling? How about the prechambers? Are the balls intact?

Alastair · #9 10-07-2008, 11:44 AM

Could be wrong, as its hard to tell with the sound reproduced from a digi-cam and Utube....(Engine sound/mechanical noises lose just so much when recorded/played back.....)t

I have three running 617 (used and abused) engines. All have a similar noise to a greater or lesser extent.

If the oil-pressure is good When Hot at idle, and the Chain is good and timing of cam and pump as well as the cam and clearances,--you've already overhauled the injectors--

It aint gonna be a rod-bearing if you have at least 1.5 bar oil-press when Fully-Hot after say, half-hour run at idle....

I really wouldn't worry about it. It is after all, a 20 odd year old Diesel-engine. It aint gonna be perfect at that age, and by your own admission was not that well taken care of....(Some would say, what is expected for a 200 quid car!)

It seems (At least with every 617 N/A engine I've seen, as well as the 4 I've owned) that piston-slap to a greater or lesser extent depending on past use/maintenance, on one or two pistons is common at the ages and mileages we see now....

Give it a lube-change, and try a can of Wynns in it, or STP--May quieten it down...

You may find, that under load the knock is reduced--generally is if its piston-slap...

I have run a 300D N/A with a similar level of 'knock' to that shown for over 80K miles. It never seemed to get any worse, and still runs, but at 380 odd K is 'tired' (bit smoky etc...)--I keep it as a 'spare'

airbus · #10 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?

airbus · #11 10-07-2008, 11:46 AM

Quote:

Originally Posted by pawoSD

Could it be a bad/knocking vacuum pump? Or perhaps something else on the engine is rattling? How about the prechambers? Are the balls intact?

Hey, my balls are none of your business

.

Alastair · #12 10-07-2008, 11:52 AM

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

barry123400 · #13 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 · #14 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 · #15 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.