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  #1  
Old 04-17-2015, 09:19 PM
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Hypothetically speaking, what would be the symptoms of a loose rod?

Other than the knock? On a 617 diesel.

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  #2  
Old 04-17-2015, 09:46 PM
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Loose rod as in crank bearing end or piston wrist pin end?

If crank bearing end: Oil pressure starts falling off at hot idle. Possible increase of oil smoke out the exhaust. If the engine was run to temp and shut off and cooled, noise will be louder at start up, get quieter when oil pressure builds then louder as oil thins out.

If piston end, oil pressure will be unaffected unless the rod is drilled for pin oiling. Noise is more of a light double click than a hammer.
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  #3  
Old 04-18-2015, 12:22 AM
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Thank you.

I may have more serious issues than a ping.
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  #4  
Old 04-18-2015, 01:54 AM
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You can hook up a quality undampened gauge to the oil pressure port, and read the oil pressure at idle. It should be steady at the needle. If the needle is really bouncy, that's indicative of a worn rod bearing. As the rod bounces up and uncovers the oil gallery, the pressure will drop (because pressure is resistance to flow) and then when it comes down to cover it the pressure will spike. Beside physical inspection, that's probably the best way to diagnose a rod bearing.
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  #5  
Old 04-18-2015, 04:17 AM
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The only way to be 100% sure (until it becomes really obvious) is to dismantle and measure. There are, however, oil analysis people who can tell you the likely place from where bits in the oil have come. If oil analysis is not too too expensive in your area I'd try that first.
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  #6  
Old 04-18-2015, 06:42 AM
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Cut open the oil filter and pull the pleats out and look for metal. Any silvery and soft flakes are bearing material. May find ferrous metal too. Also shine bright light into the oil, if it looks anything like metallic paint, you have problems.
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  #7  
Old 04-18-2015, 08:58 AM
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Another consideration though I don't know if it applies to your engine.

Have a look at the pics in post 43 in this thread, the read the entire thing paying particular attention to my posts. ( As a side note it tends to prove that Toyota and MB don't mix ) http://www.peachparts.com/shopforum/diesel-discussion/313655-how-could-my-om617-compromised-so-quickly.html

In short the engine in question was damaged long long before the Toyota install, probably due to something bouncing around in the combustion chamber.

Also, the increased oil smoke from the exhaust I spoke of in this thread is caused by excess oil flying around overloading ( worn ) piston rings.
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  #8  
Old 04-18-2015, 11:29 AM
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Thanks for the replies, folks.

I read the thread referenced. Believe me, if there was something punching holes in pistons, I'd hear it!

My 617 has always had a bit of a tap to it that I didn't think was quite normal either, but being my first diesel, I wasn't quite sure. This last time I started it, the knock was pretty distinct. THAT I knew wasn't normal. Oil pressure was fine(oil pressure gauge plumbed to stock location on stock oil filter housing), oil was at correct level on the dipstick. It's also always had an "off" spot during cranking. All cylinders are pretty close on compression, but when cranking to bleed injectors and such the sound was whine whine whine whine (lower whine) whine whine whine whine (lower whine) whine whine. I should get video and post it up.

Going to pay one of the local experienced MBZ guys to have a listen to it and confirm, and do some basic trouble shooting. Kill injectors one at a time to see if I can localize it to one cylinder, then switch injectors and see if the sound moves, etc. Stethoscope on the bottom end.

Work is insane lately and I have a LOT of personal crap going on too. I simply do not have time for a detailed tear down and possibly fixing what's there, and going to need my truck up and running pretty quickly too. There's a local-ish guy with a 617 with 130k miles on it for sale that I think I'm going to jump on - I can swap motors in ~1 day. That's less than half the miles of my current engine, and I can swap over my Greazzer-built injectors and a couple other goodies and have some spare parts.

Any thoughts?

Thanks folks.
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Old 04-18-2015, 12:11 PM
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Quote:
Originally Posted by OM617YOTA View Post
There's a local-ish guy with a 617 with 130k miles on it for sale that I think I'm going to jump on - I can swap motors in ~1 day. That's less than half the miles of my current engine...

Any thoughts?
Go for it!
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  #10  
Old 04-18-2015, 12:18 PM
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Someone in another thread recorded engine noises and used audio editing SW to visualize sound then pinpointed where in the engine cycle the noise was coming from. They might have used vid to sync it to the engine.
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  #11  
Old 04-18-2015, 12:33 PM
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Found the audio test, post 9

http://www.peachparts.com/shopforum/tech-help/291506-w210-piston-damage.html
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  #12  
Old 04-18-2015, 01:26 PM
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I am in the process of rebuilding a gasser that spun a rod bearing.
It knocked and there was sort of a gray colored mud (the bearing babbit) in the bottom corners of the Oil Pan.

Others have found more metalic looking particles in the bottom of their Pans.

Seeing what is in the bottom of the Oil Pan could tell you.
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Last edited by Diesel911; 04-19-2015 at 11:33 AM.
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  #13  
Old 04-18-2015, 02:08 PM
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Quote:
Originally Posted by OM617YOTA View Post
... There's a local-ish guy with a 617 with 130k miles on it for sale that I think I'm going to jump on - I can swap motors in ~1 day. That's less than half the miles of my current engine, and I can swap over my Greazzer-built injectors and a couple other goodies and have some spare parts.

Any thoughts?

Thanks folks.
If you want piece of mind buy the spare engine - leave it in storage and keep driving what you've got.
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  #14  
Old 04-18-2015, 02:12 PM
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Not exactly local

http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/367592-om617-95-engine-trans-free-al.html
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1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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  #15  
Old 04-18-2015, 02:18 PM
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Somebody ought to snap that one up. It's spring and nice weather for a little road trip. I'd be tempted but I've already got a spare engine. Could be interested in the tranny...don't have a spare one of those right now (the spare I had is already in the car)

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