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I recently purchased a 1985 300d with 127k miles on it. The previous owner had the car for 8 years and took excellent care of it. Even replaced the cruise control last year. He mentioned that the car has always had a heavy vibration when idle, though it never impacted the condition. I have read a few things that may cause this: engine mounts, transmission mounts, etc ... though am trying to confirm if this could cause damage to the car? He also had the engine tuned up last year.

I am also trying to find instructions how to change the fuel filter. Any ideas?

Thanks much.
 

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1985 300D W123 Cali
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a valve adjustment and engine mounts are a good place to start.

The primary (typically clear) fuel filter is in line and easily changed by loosening the pipe clamps and switching it out. The secondary filter (looks like a spin on oil filter) is also pretty easy to switch out. Fill the secondary filter prior to attaching it. You can then prime the fuel system by unscrewing(anti-clockwise) and then pumping several times. If the primer is an updated (black) primer, you simply press down several times.

If you have trouble getting it started, try priming some more. If that doesn't work, I've heard you can loosen the hard injector (#1) line and crank to get air out.

There is a lot of info here. Prior to tackling a project, first do a search and then ask questions if you can't find your answer.
 

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For the main filter, always loosen the bolt on top first. Do not attempt to use an oil filter wrench to loosen the filter without loosening the bolt first! It does not work! Use the correct size wrench on the bolt - no adjustable wrenches, as they may slip and damage the bolt.

Make sure that the idling speed is in the correct range (750-800 RPM). Too low an idling speed can cause vibration at idle too. Improperly adjusted injection pump timing can also contribute to vibration at idle.
 

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2013 MINI Copper S Clubman, '84 300CD-weekend car
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Posts #'s 2 & 3 offer good advice.
Check to see if there's a crush washer under that big bolt.
 

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'84 300D/ dakota benz trk. Sold... miss it. "88 260E '91 190E 2.6 '89 Volvo 240DL "85 300D
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i dont know what sound you are hearing, but mine had an annoying vib/rattle a while back and i found that the metal fuel lines had somehow came in contact with the cab. its where they run down behind the oil filter. i slit some fuel line and put around both of them, silence is golden...
 

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Discussion Starter #6
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It is a heavy shake when I am at a stop (also when in park after driving a bit). It tends not to happen in the morning, though as I drive more and the engine warms up, the engine has a heavy vibration. Going to try to replace the engine mounts and hope that it resolves it.
 

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You may have a rack damper bolt issue, should be able to find info on that with a search.
 

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Also, check the air cleaner rubber mounts. You would be surprised how much vibration bad air cleaner mounts can cause. In some cases the mount bracket breaks where attached to the engine block. Check this one too by removing the air cleaner assembly.
 

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It is a heavy shake when I am at a stop (also when in park after driving a bit). It tends not to happen in the morning, though as I drive more and the engine warms up, the engine has a heavy vibration. Going to try to replace the engine mounts and hope that it resolves it.
Mine's the opposite, worse on start but gets much better when the engine warms up.
 

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Mine's the opposite, worse on start but gets much better when the engine warms up.
You may have glow plug issues, how long, roughly, does it take to stop shaking?
A rack damper problem usually shoes itself after warm up.
 

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'84 300D/ dakota benz trk. Sold... miss it. "88 260E '91 190E 2.6 '89 Volvo 240DL "85 300D
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try adjusting the rack bolt you have. run it in whilst idleing and see if shake improves.
 

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Also, check the air cleaner rubber mounts. You would be surprised how much vibration bad air cleaner mounts can cause. In some cases the mount bracket breaks where attached to the engine block. Check this one too by removing the air cleaner assembly.
Just had a look at mine & took the top off to see what the filter looks like..

Felt like the bottom wasn't attached to anything & could lift it up quite a bit..

Takin the assy off next..

What is this rack dampner about?
 

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Also, check the air cleaner rubber mounts. You would be surprised how much vibration bad air cleaner mounts can cause. In some cases the mount bracket breaks where attached to the engine block. Check this one too by removing the air cleaner assembly.
Just went through mine & they were shot; missing nuts, thread bases detached from the rubbers etc. Changed them out & all snug now.
 

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You may have a rack damper bolt issue, should be able to find info on that with a search.
An engine/IP in good tune should not need the rack ramper at all. Check compression and have the injectors pop tested if there has been no recent service. Then have the IP put on the bench.
 

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An engine/IP in good tune should not need the rack ramper at all. Check compression and have the injectors pop tested if there has been no recent service. Then have the IP put on the bench.
I've had rack damper bolt issues, the spring wears out over time. Replaced it with a new one, made a few adjustments, all's well now.
 

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I have a similar issue in my 77 300d. I also have a large amount of white/light grey smoke on start up. I've been told it can be an injector/injection pump issue.
 
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