83 300D Vibrating Air Filter Canister @ Idle

Hi All,
I have a 1983 300D which has developed a really bad shaking air breather at idle. It currently rattles against the throttle cable bracket on top of the
valve cover. I have replaced the air breather mount, which was broken, and all of the rubber mounts which holds the air breather to the mount. There is obviously a root cause somewhere, which caused the old one to break. If I raise the RPMs a little (~100 or so) it smoothes out. I have just replaced all fuel filters and as part of a tune up, but have not adjusted the valves in the past 10k miles. The car runs good otherwise. I don't think the dampener bolt in the injection pump has been replaced. Will this cause the air breather to vibrate at idle? The engine itself (and the car) do not shake excessively - just the air filter canister.
Any ideas?
Thanks, Jeff
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This is a problem from an inherently unbalanced (5 cylinder) motor, a too heavy air cleaner can and a poorly designed support bracket.
In my 26 year ownership the support bracket under the air filter can has broken three times - always the rear leg. The newest one has a reinforcement welded to that leg to help it take the motor's side to side oscillation. I also screwed onto the air cleaner can a metal (plumber's) strap enclosed by a piece of heater hose as a bumper between the air cleaner can and the engine's valve cover - again to reduce the air cleaner's oscillation.
Notice that I didn't even mention the three rubber mounts for the air cleaner car - their failure is assumed after about 10K miles.
1. Try to lift the air cleaner from its mounts - the can will lift if one of the rubber mounts is broken. These are about $10 each at the local stealer but cheaper on line.
2. When the motor at idle sounds like a semi automatic, the support bracket has broken and needs to be replaced. Suggest a steel semicircle arc be welded to the new bracket to stiffen its rear leg - but not so large that it won't fit.
3. The rack damper pin is adjusted correctly if the motor doesn't shake heavily (1/2" or greater oscillation) at hot idle. The shaking is awful and suddenly stops with a slight turn of the bolt - day vs. night. So, unless the whole car acts like a jumping bean at hot idle, leave it alone for its either OK, or not.
If I have further problems with this lousy design I'm going to mount the air cleaner can on the fender and pipe the air to the turbo.
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I mention this from time to time but if you add a fourth mount on the air cleaner so a 1/2" bit of rubber sits between the cleaner and valve cover, then they stop breaking. Which they did a lot before.
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Looking for the root cause? Check out your motor mounts. The shaking will be bad if the mounts are worn out. Not too expensive to buy, but a little bit of a pain to change. At least the first time it was. I have a '84 300D. Changed the mounts 2 years ago. Been smooth since then. I, too, had a problem with the air filter mounts. But it hasn't broken since I changed the mounts.
Bill

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You can get the car to the point where you can nearly balance a dime on it and that thing still vibrates. It's at a nodal frequency or something.
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Varnish inside the injection pump. Run two cans of octalnitrate throgh it. "Lubro Moly Diesel Purge" is what I like right now and I'm 99% certain if you run two cans thourgh it it'll smooth right out. You don't do this every now and then I take it? You need to to to clean the gum, varnish and other deporist than tens of thousands of gallos of gasoline leave on the inside of fuel handling machinery.
Don't go for any addiaitve in a tank stuff, you haveto run the engine on this crap for 15 minutes directly, but it's easy and bloody magic in what it does. Anything with octal nitrate should work, but most stuff i've sen is stupid expensive and the German Lubro Moly stuff seems to be the cheapest source at $4 a can or something like that.
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About the only thing I have run through it is B90 a few tanks ago. I ran about two or three of those tanks through it, but just changed the filters. I will order me a few cans of Diesel Purge and try that. Thanks,
Jeff
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(tom waits vioce) get a case.
you'll use two cans right there and if your engine is half nominal it'll purr and be so smooth you won't believe it. and now you're out.
lubro moly wants you to do this every 6 months. you'll want to do it every 3 months. it's that smooth. so try to find a good case price
the stuff is addictive. worse than heroin. people get over heroin nobody can stop using this stuff once they've tried it.
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