1979 450 SL engine knocking/right side - Mercedes-Benz Forum

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post #1 of 8 (permalink) Old 05-18-2006, 01:50 PM Thread Starter
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Question 1979 450 SL engine knocking/right side

Recently purchased vehicle with app 80000 miles has knocking similar to valve clicking in right side of engine, but mechanic says cause of noise cannot be adjusted and that the source of the noise may be from a wrist pin. He also says engine could run like that for 100,000 more miles, but the noise is annoying. Any suggestions?
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post #2 of 8 (permalink) Old 05-18-2006, 04:57 PM
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Hi be carefull

you have a problem with the Valves on one side, you have to check the Valves

the are not Hydrauliksystem in your Engine it works Mechanikal.


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post #3 of 8 (permalink) Old 05-24-2006, 10:29 AM
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I'm fairly certain your car has hydraulic valve lifters. I worked on a 1975 or 1976, and remember reading that the next year Mercedes went to hydraulic. It is true and not true that there is no adjustment. There is no major adjustment, but there are shims on top of the valve stems that adjust the lifters to get them all to the same height from the head. If they are not hydraulic, then they definitely can be adjusted, and should be.

I doubt the shims are an issue here, but it is possible a hydraulic valve lifter has gone bad and has collapsed. It does happen, and they are replaceable. A good mechanic can take the valve cover off and check each to make sure it is working properly. The wrist pin noise is possible, but sounds like he is just guessing. There is a tool that looks like a stethoscope that can be used to pinpoint the location of a noise without guessing.
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post #4 of 8 (permalink) Old 05-24-2006, 11:12 AM
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Camshaft oil supply rail over the camshafts have tiny hiles where oil drips on camlobes. Usualy, holes get clogged and it starves lobes to dry condition. Metal on metal and no lubricant = valves start knocking.
Must do:
1. NEW plastic feeder on coper-like oil supply rail
2. good clean of same rail, holes too (3M makes good products for this, I would not use sandpaper)
3. You'll have to replace rockerarms and camshaft as needed but pointless to do unless 1. and 2. not done.

I've done it on both banks. :-(
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post #5 of 8 (permalink) Old 05-25-2006, 10:42 AM
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Same Problem


It sounds like I may have the same problem that you are experiencing. I have a 1978 450SLC and I have been hearing a tapping noise from the right valve bank. Is it possible to visually inspect the camshaft supply rail by just removing the valve cover? How would you recommend I would proceed with determining if that is indeed the cause of the noise.

Thanks in advance.
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post #6 of 8 (permalink) Old 06-09-2006, 05:08 AM
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if you're sure its on the right side, take the valve cover off and start the engine. you should be able to pinpoint which valve is making the noise. doing this will also let you see if the camshaft supply rail is actuall oiling the cam lobes
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post #7 of 8 (permalink) Old 06-09-2006, 04:08 PM
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Diagnosing wrist pin noise

..is simple,using rubber gloves or insulated pliers,just remove each plug connector in turn until the noise stops.If it doesn't stop the noise ,it's either tappets ,worn chain and tensioner rails or a cracked Piston .
in any case,ANY noise is of concern.The engine should idle smoothly and quietly with no noise what so ever.
This what happens when you ignore noises in a Mercedes V8...thats a valve head on the right hand side stuck in the broken remains of the piston.
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post #8 of 8 (permalink) Old 07-22-2010, 09:30 PM
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my 79 450sl just started doing this same knock today. i have been slowly rebuilding the car and just put a replacement distributor in it today because the advance was bad on the old one. car fired right up and actually idled for the first time without my foot on the gas. after about five minutes the car shuttered and then started knocking from the right side and then stalled. It restarts and stays running if you keep your foot on the gas a little bit but is still knocking. Any suggestions on the sudden onset of knocking and why it wont idle?
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