380 SL Knocking - Mercedes-Benz Forum
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#1 (permalink) Old 03-13-2011, 02:37 PM
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380 SL Knocking

I have a 1981 380 SL that has developed a tapping noise that sounds like it is coming from under the center of the RH valve cover. The sound is louder at an idle and gets quieter under a load but is very annoying at a stop light. This is my first Benz but if it was an older American muscle car I would think it was a lifter. Thoughts or ideas where to start?
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#2 (permalink) Old 03-22-2012, 01:02 PM
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I have a 83 380sl and it is doing the EXACT same thing. It started tapping about 2 weeks ago when I was driving it about 65mph for about 30min or so and now it keeps making that annoying noise. I don't know where to start. Any ideas on whereto start anyone?? Thanks in advance!! James
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#3 (permalink) Old 03-22-2012, 01:05 PM
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Have you had your timing chain done?
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#4 (permalink) Old 03-22-2012, 01:10 PM
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I bought the car about 3mon ago with no history so I'll take it that it probably has not been done. I was reading some other treads about maybe a stuck lifter or something like that. I did notice that when I was on the interstate at a high speed that the sound did go away. I didn't even hear it when I was driving about 45mph. Weird????
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#5 (permalink) Old 03-22-2012, 01:21 PM
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It actually sounds like it has something to do with the timing. When I rev up the engine and listen to it, the knocking goes away but as soon as I stop revving it up, it sounds like something is rolling around towards the front of the engine. It cranks up and runs just fine otherwise with no problems.
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#6 (permalink) Old 03-22-2012, 01:39 PM
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Originally Posted by bmwbeemer7 View Post
I have a 83 380sl and it is doing the EXACT same thing. It started tapping about 2 weeks ago when I was driving it about 65mph for about 30min or so and now it keeps making that annoying noise. I don't know where to start. Any ideas on whereto start anyone?? Thanks in advance!! James
Without filling out your profile and with a username like that, you will be unlikely to get much help around here. It does sound like you should check your timing chain ASAP though. I doubt that knocks in your engine are going to make anything better. Probably best to not use the car until you get this diagnosed and/or fixed. Timing too early can cause knocks. My old car has vacuum retard to make the timing later at idle. It would probably otherwise be more likely to knock. If you feel comfortable adjusting the timing on your car, you should feel comfortable checking the timing chain. See the stickies at the top of this forum, and read about the timing chain replacement thread linked in there. The beginning of that thread shows how to check for timing chain stretch. That would be a good place to start if you will be messing with the timing.
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#7 (permalink) Old 03-22-2012, 01:45 PM
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If you would fill out your profile, there may be someone close that could stop by and take a look at it for you..................

I asume your oil pressue is good, or does it increase as the noise decreases?????????????

If you have no history on the maintenance of the car, it could be timing chain slap your hearing, and that's not a good thing. These motors are interferance fit motors,, IE. If the timing of the valves are off too much, they will hit the pistons and you will be left with a nice conversation piece.

I would invest in some new valve cover gaskets. Then remove the valve covers and check out you chain. There are alot of threads on what to look for and how to fix it..

Your car had a single row timing chain from the factory, they can be refitted with a double row chain, but that's not cheap, but either is a new motor....

RC

If I knew I was going to live this long, I would have taken better care of myself and saved more money
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#8 (permalink) Old 03-22-2012, 01:46 PM
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Thanks Fonzi! I'll start with the timing and see if that's the case. It really does sound like that's the problem. I'm afraid to drive it anyway with it running like that so I'll look at it this weekend and see what I got. Thank you sooo much. I was really thinking about just selling the darn car at a very very low price and not even messing with it.

PS...I do need to do something with my username. lol
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#9 (permalink) Old 03-22-2012, 01:50 PM
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Ok Rockcrusher. I'll look at it and see. I really do like the car and I hope it's not anything to expensive. My wife already doesn't like the car. I love it myself. I'll take a look at the chain and go from there. Thanks!!
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#10 (permalink) Old 03-22-2012, 01:55 PM
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I do like filled in profiles.

BEM be afraid, be very afraid. If your chain has not been converted to dual row it will fail. If it has then you still need to check for wear, tensioner and guides.

A "lifter" noise can be caused by worn cam lobes, cam oiler tube fitting failure, or the lifter (hydraulic compensator)

Pull the valve covers.
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