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  #1  
Old 06-16-2002, 11:17 AM
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Angry intermitten engine tap

Hello everyone. Recently I just did the head over on my 86 300E. Car ran fine and all, then recently I've noticed the car has a tapping sound that comes and goes(mostly stays though). It does this at all operating temps. One minute car's quiet then all of a sudden I can hear a tapping sound coming from the front of the engine. Haven't been able to pinpoint exactly where it's coming from, then just as quickly as the sound started, it goes away(now it just stays). Is there anything that has to be readjusted when you do the head over on your car? Does the rocker arms have to be readjusted?

Thanks

P.S.: Here are other symptoms. When I'm at idle it seems as if I'm running a modified cam(like it has a miss), but when I get on it or just give it enough gas to go, it runs fine and smooth. Can a rocker have not been tighten to spec and have backed off alittle? Otherwise like I stated early the tapping noise which is coming from under the valve cover and the rough idle, does this sound like during refitting I failed to tighten a rocker arm properly, also when I give it gas the tapping increases with the motor . Love my car but it's starting to piss me off.

Once again,Thanks
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1986 300E

Last edited by rich30769; 06-16-2002 at 10:22 PM.
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  #2  
Old 06-16-2002, 10:50 PM
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Richie:
The car has a part in each rocker arm called a hydraulic compensator, it's sort of like an automatic adjuster, or like a lifter in a pushrod engine. There is a basic adjustment that should be done if any "real" changes are made to the system, such as grinding the valves, I also recommend doing this check if a new cam is installed. It takes a dial indicator and a special tool holding fixture for the dial indicator to check the addjustment. There are different thickness spacers that are used to adjust the basic position. Since the noise comes and goes, I would assume one of them is going bad, hard part would be finding which one. Another possiblity would be the small cup-washer on top of the valve stem was not installed, but again I would assume this would be a constant noise, not coming and going.
You're sure the long sheetmetal oil tube was reinstalled correctly?
Gilly
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  #3  
Old 06-17-2002, 09:28 PM
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Gilly,
Oil tube was installed correctly. So in other words, I'm not going to be able to check or adjust this noise without this tool which I definitely don't have. Started off no noise at all then all of a sudden, TAP TAP TAP just like that out of the blue.
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1986 300E
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Old 06-17-2002, 10:20 PM
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Richie:
What you can do is take the end of a hammer handle (grabbing the head of the hammer) and push down on the valve side of each rocker arm, and hold down on it hard for about 10 seconds.
Then release pressure on the handle and see if that arm is loose or not. If you find one that's loose, that's the trouble maker, you can try replacing just the hydraulic element on that particular arm.
Do this one at a time until you find the bad one or ones. Be sure to check if all the cup-shaped washers are there on top of the valve stem.
Gilly
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  #5  
Old 06-18-2002, 06:40 PM
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Gilly,
Before I even had the chance to try that, I put the resistor (that everyone's removing)back in and the tapping went away and the idle is a whole hell of alot smoother. I want to wait a few days to see if the tapping comes back. If so I'll try your method.

Thanks again..
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1986 300E
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  #6  
Old 06-18-2002, 11:00 PM
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Richie:
So you mean the resistor on the plug wire end? Maybe just a secondary ignition zap, not mechanical?
Gilly
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  #7  
Old 06-19-2002, 02:08 AM
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I think he's talking about the R16 resistor.

Perhaps he's hearing pinging??? Maybe not running Hi-test????
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  #8  
Old 06-19-2002, 06:44 PM
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Mike,
Your correct when you say the R16 resistor, but this was tapping not pinging. I had my share of cars that pinged . This was definitely a TAP TAP TAP. And if this was pinging? Mercedes pinging sounds awhole hell of alot different than American and Import pinging. Anyways, this is the second day so far and all sounds good. I'm still going to give it a few more days. Idle is still smooth also.
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1986 300E
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  #9  
Old 06-19-2002, 07:00 PM
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It might just be the small shock of the belt tensioner. If the rubber bushing is worn it will produce irritating tapping noice.
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