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Discussion Starter · #1 ·
Well my car decided to develop a knock two days ago, and it sounds like an old Mercedes diesel with 250k miles on the clock. The engine was supposedly a low-mileage engine when I bought it, it has been well-maintained since then, and I really don't beat on it, so I'll be surprised if it's something internal. The car behaves fine in traffic (save for the God awful clatter), pulls normally, and the clatter disappears suddenly around 1,500 rpm under load and doesn't reappear until the pre-shift fuel cut when the torque converter starts to let go, so I'm stumped as to what it is. It sounds like it's either coming from the #1 or #2 cylinder. I remember reading something about some sort of weird spring on the back half of the engine that made a lot of noise when it went, but I can't find where I read about that.

So...any ideas on what it is and how I should go about fixing it?
 

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I believe its the HLAs around the #1 cylinder. If i remember correctly the oil pump sometimes can have a little trouble pumping oil through there. Passage might be clogged. You said the clacking dissappears around 1500 rpms so its most likely the HLAs.
 

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Discussion Starter · #3 ·
I was kind of afraid of that. Is there any way to repair it?
 

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Run a quart of Marvel Mystery Oil through your system for about 500 miles then run a seafoam treatment. oil change then drop more mystery oil in. :)
 

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Discussion Starter · #5 ·
Well crap. I just changed the oil with synthetic blend not 700 miles ago. Thanks for the tip, though. I've only had the tap for a few days, but I'm ready to get rid of it.
 

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i wonder if it could be your friction gear also. it's another thing that's known to make noise in our engines and it's also by cylinder #1. there's stuff in the faq about replacing it with one that's better
 

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Discussion Starter · #7 · (Edited)
Scratch it. I went out tonight to give everything a onceover before I decided what to do, and it's around the #2 cylinder (which is kind of a relief), and the noise doesn't go away after 1500 rpm...it just turns into a steady buzz. Is there any way to visually check the friction gear spring without removing the valve cover and camshaft?

And is it possible that a timing belt tensioner could make a lot of noise? I pried back the fragmented mass that is my timing belt cover and noticed that the belt flutters an awful lot.
 

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Did you ever get this sorted? It sounds like my problem, except mine goes away around 2500 RPM.

I did think it was the HLAs, but now I'm leaning towards the TB tensioner. I should find out tomorrow though, I'm getting the tensioner replaced with a King6 manual one.
 

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It was the tensioner, now I have a nice quiet engine. :)

The old tensioner only had 20,000 km on it, they really are crap.
 
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