Loud Engine knocking noise !!! - Mercedes-Benz Forum
 
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post #1 of 7 (permalink) Old 02-24-2019, 04:15 PM Thread Starter
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Exclamation Loud Engine knocking noise !!!

I haven't driven one of my cars for about 5 weeks, it's a 1997 S420, and when i started the engine, it started right up, but it made a very loud knocking noise for a while, and later it went away. Now when i start it up it does not make that knocking noise anymore, but when i open the hood, i can hear the engine being a bit louder than usual....like a light knocking noise. The car drives otherwise very good as always. What could be the issue with this knocking sound ?
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post #2 of 7 (permalink) Old 02-24-2019, 08:35 PM
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Here is my theory of your problems.

Since it is cold in your area, you might have a summer blend of oil, so you might have popped the flat covers of your plastic CAM oilers. I would go in for a inspection, and for that you need to remove the valve covers, and look at each oiler for a missing cover. See this for a blown-oilier:

https://www.k6jrf.com/MB_lifter.html

While the valve covers are off, I would check the timing of the engine. Here is a thread :

https://www.benzworld.org/forums/r12...-end-work.html

If you find you have a really stretched chain, one does not need to pull the timing cover. You can get to the chronic chain guides except for one which is on the slack side which is the right. If you want to get to that one chain guide, you will need to remove the timing cover. Lift the engine as the upper oil pan needs to come out. A bigger mess to deal with...

https://www.benzworld.org/forums/w14...engine-v8.html

Hope this helps,

Martin
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post #3 of 7 (permalink) Old 02-24-2019, 09:08 PM Thread Starter
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Originally Posted by MAVA View Post
Here is my theory of your problems.

Since it is cold in your area, you might have a summer blend of oil, so you might have popped the flat covers of your plastic CAM oilers. I would go in for a inspection, and for that you need to remove the valve covers, and look at each oiler for a missing cover. See this for a blown-oilier:

https://www.k6jrf.com/MB_lifter.html

While the valve covers are off, I would check the timing of the engine. Here is a thread :

https://www.benzworld.org/forums/r12...-end-work.html

If you find you have a really stretched chain, one does not need to pull the timing cover. You can get to the chronic chain guides except for one which is on the slack side which is the right. If you want to get to that one chain guide, you will need to remove the timing cover. Lift the engine as the upper oil pan needs to come out. A bigger mess to deal with...

https://www.benzworld.org/forums/w14...engine-v8.html

Hope this helps,

Martin
Thank you Martin,

But i have replaced all the plastic cam oilers with the metal ones about 10,000 miles ago, and i have been using CastrolSyntec 10W-40 oil all the time. Chain guide has also been replaced at that time.
What do you think ?
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post #4 of 7 (permalink) Old 02-24-2019, 10:19 PM
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And the timing chain? Have you checked the timing? Was checked in the past?

It can be it is just too cold in your area.

I had a little knock for a M119 that has not been started in like 2 years, but lasted for a handful of minutes

Martin
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post #5 of 7 (permalink) Old 02-25-2019, 06:26 AM Thread Starter
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Originally Posted by MAVA View Post
And the timing chain? Have you checked the timing? Was checked in the past?

It can be it is just too cold in your area.

I had a little knock for a M119 that has not been started in like 2 years, but lasted for a handful of minutes

Martin
How do i check the timing chain ?
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post #6 of 7 (permalink) Old 02-25-2019, 09:54 AM
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How do i check the timing chain ?
Try reading Martin's first post in this thread and the links he provided.
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post #7 of 7 (permalink) Old 02-25-2019, 04:18 PM
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