Okay, okay, this is a W123. But as it's the exact same engine as the 300SD, I'm hoping somebody could give some advice on what might be wrong with my engine - the last day I drove it it started making this horrible knocking sound. Since then I've changed the oil and done a diesel purge, to no avail.
Car seems to still perform very well, but I'm not driving it much like this. Any advice very welcome!
http://www.youtube.com/watch?v=LUUnLepAT50
I've no idea what that is, but I would get a stethoscope and try to pinpoint the sound. It might be an idea to remove the rocker cover and have a look.
There must be a huge amount of play in whatever it is, rod bearing perhaps?
Tim
Surely you can't mean an actual stethoscope, as I imagine the sound would be quite deafening. Do you mean something like this?
(http://3.bp.blogspot.com/_ttYBeZtXmBU/THaLk1_v-QI/AAAAAAAAAhI/yYNPKdBU1yE/s1600/broom.jpg)
...or is there some special product for cars you can buy?
I use a big old flat screw driver, great to use on a 280E before and after valve adjustment. get one and put the handle against your ear and the other on the engine, in different places.... just gets tricky with a realy bad idle :)
sounds like a seized hydraulic valve element - if the diesels have them i've no idea, but i'd be inspecting the valve train.
Quote from: Major Tom 6.9 on 18 August 2011, 04:58 PM
sounds like a seized hydraulic valve element - if the diesels have them i've no idea, but i'd be inspecting the valve train.
Would this be by taking of the valve cover, and having a look at what's underneath? If you could point at some pictures (on any engine) of what you're talking about or give me a "for dummies" breakdown I'd appreciate it. I've got no almost no experience with engine stuff yet.
I've never seen one of those engines in my life so I wont be able to help you 8)
It does however sound exactly like a company car i drove many years ago which had a sticky hydraulic valve compensating element and sounded like a sewing machine on steroids until it free'ed up usually after 5 - 10 minutes from cold. Hence my thoughts that its absolutely valve train related.
perhaps not a task for the uninitiated, might be worth getting a in independent mb specialists opinion.
I just looked at the epc, those engines look about as simple as simple can get.
there doesnt appear to be any kind of hydraulic valve compensation, it looks like the valves are adjusted manually by nuts on the stems ?
I'd take the cover off and rotate the engine by hand if possible from the front crank nut (running direction only!) and see WTF is going on in there. should be pretty obvious with that much racket.
Quote from: Raptelan on 18 August 2011, 01:23 PM
Surely you can't mean an actual stethoscope, as I imagine the sound would be quite deafening. Do you mean something like this?
(http://3.bp.blogspot.com/_ttYBeZtXmBU/THaLk1_v-QI/AAAAAAAAAhI/yYNPKdBU1yE/s1600/broom.jpg)
...or is there some special product for cars you can buy?
There are mechanic's stethoscopes available, but the old screwdriver trick is just as effective of course. 8)
MT, surely the nuts are lock nuts on tappets? 8)
Hopefully the camshaft hasn't suffered and it is in fact just a tappet/lifter issue (easy fix).
I would suggest googling or searching on YouTube for "adjusting tappets", or whatever to get an idea of what it's all about.
Tim
I'd start with the top of the motor. Remove the camshaft cover and see if anything looks out of place.
Adjusting the valves is easy, even for a non-mechanic. Here's a link to a set of instructions that are well done:
http://dieselgiant.com/valveadjustment.htm
If you don't find anything out of place under the cam cover, you can check to see if the issue is deeper in the motor with a fairly simple test.
First, get a good line wrench and loosen and retighten each injector line at each injector. There will probably be some diesel spray or leakage during this part - wear eye protection and have rags present.
Then, start the engine and allow it to come up to operating temperature.
With the engine running - fit the wrench to the first injector line, then cover wrench and line with a wrag. Crack the line open just a bit. Diesel will spray out around the loose connection, but the key is it won't spray into the engine, so that cylinder will go "dead." If the knocking is a rod, or wrist pin, the noise will go away when you get to the cylinder where the problem is.
To me, the sound appears to come from the top of the motor. Hopefully you'll find the cause when you get the cam cover off.
Quote from: wbrian63 on 19 August 2011, 07:37 AM
I'd start with the top of the motor. Remove the camshaft cover and see if anything looks out of place.
Adjusting the valves is easy, even for a non-mechanic. Here's a link to a set of instructions that are well done:
http://dieselgiant.com/valveadjustment.htm
If you don't find anything out of place under the cam cover, you can check to see if the issue is deeper in the motor with a fairly simple test.
First, get a good line wrench and loosen and retighten each injector line at each injector. There will probably be some diesel spray or leakage during this part - wear eye protection and have rags present.
Then, start the engine and allow it to come up to operating temperature.
With the engine running - fit the wrench to the first injector line, then cover wrench and line with a wrag. Crack the line open just a bit. Diesel will spray out around the loose connection, but the key is it won't spray into the engine, so that cylinder will go "dead." If the knocking is a rod, or wrist pin, the noise will go away when you get to the cylinder where the problem is.
To me, the sound appears to come from the top of the motor. Hopefully you'll find the cause when you get the cam cover off.
Thanks a lot for the clear instructions/suggestions wbrian63...somebody else also suggested the injector line check - I will try it tonight.
Today I finally got around to trying the injectors - every one was the same - I'd disconnect it a bit and the engine would start hesitating and stop if I didn't reconnect it immediately. In no case did the sound go away and it seemed there wasn't any injector that acted different than the others when disconnected.
I also removed the valve cover - I don't have a clue what I would be looking for but I don't see anything obviously broken. Sorry I don't have a camera any more, but I can record a video if need be. Any suggestion of what to look for/try now?
As a side note, I was replacing all the Bosch injectors on the 300SD with Monarks, and broke one of the new ones in the process. So now it's got 4 Monark's and a Bosch, and as a result sounds rattly, though a more random uneven sound than this one. So now I have two rattly 617 cars. :/
How did you break the injector?
Quote from: 1980sdga on 28 August 2011, 06:50 PM
How did you break the injector?
With stupidity. The internal parts weren't lined up correctly so the little pin on the top of the injector snapped when I went to bolt the injector back together. I've got a new one already though - Might see about getting them installed tonight. I've actually been running this week with the 300CD injectors transplanted into the 300SD, as that gives me a pretty smooth engine. But pretty soon it'll be the original injector housings with all new Monark nozzles fitted.
Stuff happens, it's how we learn sometimes :o
Did you pop check them and all that stuff? Didn't you get one of those testers?
I'd be interested in hearing about that!
Quote from: 1980sdga on 01 September 2011, 04:09 PM
Stuff happens, it's how we learn sometimes :o
Did you pop check them and all that stuff? Didn't you get one of those testers?
I'd be interested in hearing about that!
Yes I did, along with a set of various thickness shim washers, and an electronic caliper. Works great but I can't see holding onto this once I'm done with it, so it's for sale if you're interested. It would be really handy if you did this sort of thing all the time or intend to sell it after you're done. Two of the injectors from the CD could use some minor adjustment, but it's with 100psi which is acceptable per MB standards...
Have you checked the vacuum pump? It often makes a knocking sound before it brakes. If that brakes you can be in big trouble so get it checked. If it brakes the chain can brake as well and ruin the whole engine.
Quote from: Janse on 10 September 2011, 02:00 PM
Have you checked the vacuum pump? It often makes a knocking sound before it brakes. If that brakes you can be in big trouble so get it checked. If it brakes the chain can brake as well and ruin the whole engine.
How can I check it? The knocking is continuous and aligned with the RPM's of the engine, but I can drive around just fine. I've been driving it short distances on the weekend only.
I will check with my brother in law who loves these engines and is a mercedes mechanic. I dont know squat myself. I might be mistaken about the whole thing, as a malfunctioning vacuum pump makes more of a ticking sound than a knocking sound, but you might say that that is a poteito potato thingy... :P You will be able to drive quite some distance before the vacuum pump brakes, but I would leave the car still until You find out whats wrong.
By the way I was driving it a lot more and the oil had gotten quite low prior to this happening, so that could be related. This car leaks oil like it has an arterial wound.
Talked to my brother in law, he said that it might also be the timing chain. How many kilometers has the engine run? I prefer changing them after 300 000 km, but I have heard them breaking after much shorter distances. I think it is worth taking the car to a garage to sort out all the issues. Much better to change a few parts now instead of having to scrap the car is everything goes to hell...
Tonight I replaced the valve seals and adjusted the valves to MB specs. Visually verified all glow plugs work with injectors removed. Timing chain seems good - no play. After it was all done, the knocking persists. :(
I do have a new timing chain and tensioner that I bought for my 300SD which I could use, but I think it's beyond my ability to replace.
Hi Casey,
Earlier I did some research on an OM616 diesel MB engine which is a 4 cylinder diesel variant of the OM617. A friend of mine has a MB van 207D with this engine, that had got stuck.
I discovered something called 'piston slap' which is unfortunately not a good thing to have. I don't know much about it, other than that it makes the engine noisy. I know also that both OM616 and OM617 are one of the most reliable engines ever made and that this is not a common problem.
Some links:
http://www.youtube.com/watch?v=u4cCfipWgI8&feature=player_embedded
http://www.youtube.com/watch?v=tOhLBkBR1k0&feature=related
http://www.pistonslap.com/
I sincerely hope that this is not your problem.
Good luck!
Quote from: arman on 21 September 2011, 03:54 AM
Hi Casey,
Earlier I did some research on an OM616 diesel MB engine which is a 4 cylinder diesel variant of the OM617. A friend of mine has a MB van 207D with this engine, that had got stuck.
I discovered something called 'piston slap' which is unfortunately not a good thing to have. I don't know much about it, other than that it makes the engine noisy. I know also that both OM616 and OM617 are one of the most reliable engines ever made and that this is not a common problem.
Some links:
http://www.youtube.com/watch?v=u4cCfipWgI8&feature=player_embedded
http://www.youtube.com/watch?v=tOhLBkBR1k0&feature=related
http://www.pistonslap.com/
I sincerely hope that this is not your problem.
Good luck!
This is exactly my problem, I think. It sounds identical. Is the car safe to drive as-is? I'll replace the engine if need be.
On my local Craigslist, there's a 1985 turbo OM617 with 240k miles for $450, and a 1982 300SD with 150k miles being parted out because a tree fell on it - the engine is available.
The car was neglected like hell in by previous owners. Amongst (many) other issues, the engine bay was solid black (thick buildup) when I got it, and there was a lot of blow by and oil pooled up in the air filter housing.